Porphyrin and its derivatives are widely used in cancer therapy due to their strong photon absorption capabilities and moderate light stability. Due to their hydrophobic nature, porphyrins with tetrapyrrolic macrocycles ease self-aggregation in physiological conditions. Instead, exploiting the C4 symmetry structure for self-assembly is beneficial to improve the bioavailability of porphyrin and its derivatives. Herein, this Review outlines porphyrin-based nanoformulations for therapeutic applications in cancer treatment. The typical pharmaceutical application of the integrated porphyrinic structure is systematically summarized, focusing on the typical synthetic methodologies and structure-functionality relationship. Additionally, therapeutic modalities (e.g., photothermal, photodynamic, and sonodynamic) and their synergy mechanism in regulated cell death are overviewed. Special attention is given to emerging technologies in nanocatalytic therapy, therapeutic vaccines, and proteolysis-targeting chimeras, which align with the trend toward personalization and minimal invasiveness in healthcare. Finally, we discuss the challenges and limitations of porphyrinic nanoformulations and explore their future directions in the healthcare sector, aiming to bridge the gap between research and practical clinical application.

The oxygen reduction reaction (ORR) can take place via both four-electron (4e-) and two-electron (2e-) pathways. The 4e- ORR, which produces water (H2O) as the only product, is the key reaction at the cathode of fuel cells and metal-air batteries. On the other hand, the 2e- ORR can be used to electrocatalytically synthesize hydrogen peroxide (H2O2). For the practical applications of the ORR, it is very important to precisely control the selectivity. Understanding structural effects on the ORR provides the basis to control the selectivity. Co-based electrocatalysts have been extensively studied for the ORR due to their high activity, low cost, and relative ease of synthesis. More importantly, by appropriately designing their structures, Co-based electrocatalysts can become highly selective for either the 2e- or the 4e- ORR. Therefore, Co-based electrocatalysts are ideal models for studying fundamental structure-selectivity relationships of the ORR. This review starts by introducing the reaction mechanism and selectivity evaluation of the ORR. Next, Co-based electrocatalysts, especially Co porphyrins, used for the ORR with both 2e- and 4e- selectivity are summarized and discussed, which leads to the conclusion of several key structural factors for ORR selectivity regulation. On the basis of this understanding, future works on the use of Co-based electrocatalysts for the ORR are suggested. This review is valuable for the rational design of molecular catalysts and material catalysts with high selectivity for 4e- and 2e- ORRs. The structural regulation of Co-based electrocatalysts also provides insights into the design and development of ORR electrocatalysts based on other metal elements.

The design and synthesis of metal-organic frameworks (MOFs) with outstanding light-harvesting and photoexcitation for artificial photocatalytic CO2 reduction is an attractive but challenging task. In this work, a novel aggregation-induced emission (AIE)-active ligand, tetraphenylpyrazine (PTTBPC) is proposed and utilized for the first time to construct a Zr-MOF photocatalyst via coordination with stable Zr-oxo clusters. Zr-MOF is featured by a scu topology with a two-fold interpenetrated framework, wherein the PTTBPC ligands enable strong light-harvesting and photoexcitation, while the Zr-oxo clusters facilitate CO2 adsorption and activation, as well as offer potential sites for further metal modification. Consequently, the Zr-PTTBPC and its Co/Ni derivatives not only exhibit exceptional stability and high CO2 adsorption capability (73 cm3 g-1 at 273 K and 1 atm), but also demonstrate a CO production rate of up to 293.2 µmol g h-1 under 420 nm LED light that can be reused for at least three cycles. With insights from charge-carrier dynamics and theoretical calculations, the underlying mechanism is revealed, confirming that the single-phase multi-component synergy is the key for the outstanding photocatalytic CO2 reduction. This work showcases a brand-new type of MOF photocatalyst based on AIE ligands and their promising applications in photocatalytic C1 conversion.

Heavy metal ions are one of the main sources of water pollution, which has become a major global problem. Given the growing need for heavy metal ion detection, electrochemical sensor stands out for its high sensitivity and efficiency. Metal-organic frameworks (MOFs) have garnered much interest as electrode modifiers for electrochemical detection of heavy metal ions owing to their significant specific surface area, tailored pore size, and catalytic activity. This review summarizes the progress of MOF-based materials, including pristine MOFs and MOF composites, in the electrochemical detection of various heavy metal ions. The synthetic methods of pristine MOFs, the detection mechanisms of heavy metal ions and the modification strategies of MOFs are introduced. Besides, the diverse applications of MOF-based materials in detecting both single and multiple heavy metal ions are presented. Furthermore, we present the current challenges and prospects for MOF-based materials in electrochemical heavy metal ion detection.

This research describes the functionalization of polymer-matrix-trapping porphyrins, considering that the transcendental properties of meso-substituted porphyrins, such as optical and chemical stability, combined with the strength of the polymers, can produce photoactive advanced polymeric networks. Polystyrene (PS) and O,O´-bis-(2-aminopropyl)-polyethyleneglycol-300 (2NH2peg300, APEG), or their combination, were used to confine the meso-substituted porphyrin species 5,10,15,20-tetrakis(4'-carboxy-1,1'-biphenyl-4-yl)porphyrin and 5,10,15,20-tetrakis((pyridin-4-yl)phenyl)porphyrin. The samples were characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) and fluorescence spectroscopies. The absorption and emission properties of the materials were compared to those of their respective porphyrin solutions. The fluorescence was preserved in the obtained composite through a mixture of polymers, PS, and APEG, yielding translucent polymeric networks. Moreover, analysis of individual polymeric assemblies by molecular docking was performed to support the understanding of the experimental findings. This analysis corroborates that the stronger the estimated binding energies, the stronger the interactions that occur between porphyrin and the polymer via non-polar covalent bonds.

Access to clean drinking water is a basic requirement, and eliminating pollutants from wastewater is important for saving water ecosystems. The porous structure and surface characteristics of metal-organic frameworks (MOFs) can function as a perfect scaffold for removing toxic compounds from wastewater. Porphyrins are promising building blocks for constructing MOFs. Porphyrin-based metal-organic frameworks (P-MOFs) have been fabricated using porphyrin ligands, metal clusters, or ions. These materials can harvest light from a wide region of the solar spectrum, and their framework morphology and physicochemical properties can be controlled by changing their peripheral subunits or metal ions. These porous crystalline materials have generated interest because of their distinctive characteristics, including large permanent porosity, interesting surface morphology, broad conformational diversity, high photostability, and semiconducting nature. This article discusses the recent progress and usefulness of P-MOFs. The fabrication procedures of P-MOFs are discussed, followed by the adsorptive and photocatalytic removal of contaminants from wastewater. The relationships between the geometries of P-MOFs and their light-harvesting and charge-transfer mechanisms for the photocatalytic degradation of pollutants are highlighted. Finally, some future perspectives and obstacles in the photodegradation usage of P-MOFs are discussed, along with feasible research directions to standardize efficient photocatalysts for improved photodegradation for water treatment.

Developing high-performance aqueous Zn-ion batteries from sustainable biomass becomes increasingly vital for large-scale energy storage in the foreseeable future. Therefore, γ-MnO2 uniformly loaded on N-doped carbon derived from grapefruit peel is successfully fabricated in this work, and particularly the composite cathode with carbon carrier quality percentage of 20 wt% delivers the specific capacity of 391.2 mAh g-1 at 0.1 A g-1, outstanding cyclic stability of 92.17% after 3000 cycles at 5 A g-1, and remarkable energy density of 553.12 Wh kg-1 together with superior coulombic efficiency of ~ 100%. Additionally, the cathodic biosafety is further explored specifically through in vitro cell toxicity experiments, which verifies its tremendous potential in the application of clinical medicine. Besides, Zinc ion energy storage mechanism of the cathode is mainly discussed from the aspects of Jahn-Teller effect and Mn domains distribution combined with theoretical analysis and experimental data. Thus, a novel perspective of the conversion from biomass waste to biocompatible Mn-based cathode is successfully developed.

Current artificial nanochannels rely more on charge interactions for intelligent mass transport. Nevertheless, popular charged nanochannels would lose their advantages in long-term applications. Confined water, an indispensable transport medium in biological nanochannels, dominating the transport process in the uncharged nanochannels perfectly provides a new perspective. Herein, we achieve confined-water-dominated mass transport in hydrogel nanochannels (HNCs) constructed by in situ photopolymerization of acrylic acid (PAA) hydrogel in anodic alumina (AAO) nanochannels. HNCs show selectivity to Na+ transport and a high transport rate of molecules after introducing Na+/Li+, compared with other alkali metal ions like Cs+/K+. The mechanism given by ATR-FTIR shows that the hydrogen-bonding structure of confined water in HNCs is destabilized by Na+/Li+, which facilitates mass transport, but is constrained by Cs+/K+, resulting in transport inhibition. This work elucidates the relationship between confined water and mass transport in uncharged nanochannels while also presenting a strategy for designing functional nanochannel devices.

In this work, we report a robust bifunctional electrocatalyst composed of 2D Ni- organic frameworks (Ni-MOF) and nitrogen doped carbon nanotubes encapsulated Ni nanoparticles (Ni-MOF@Ni-NCNT) for CN and HO bonds dissociation. Due to the presence of Ni-NCNT, adsorption of OH- species is enhanced and CO2 binding strength is simultaneously weakened leading to a boosted urea oxidation reaction performance reflected by decrement in potential at 100 mA cm-2 by 69 mV. The loosened binding strength with CO2 specie is highlighted by in-situ electrochemical impedance spectroscopy (EIS) test and DFT calculation. Moreover, the alkaline hydrogen evolution reaction (HER) performance of Ni-MOF@Ni-NCNT is better than Ni-MOF and Ni-NCNT evidenced by the overpotential at 50 mA cm-2 decreased by 224 mV and 900 mV ascribed to the synergistic effect, in which Ni-MOF, Ni nanoparticles and Ni-Nx-C facilitates water adsorption, dissociation and adsorption/combination of hydrogen ions, respectively. The assembled HER- urea oxidation reaction (UOR) system requires only 1.33 V to reach 10 mA cm-2, 70 mV lower than water splitting driven by Pt/C-IrO2.

Metalloporphyrin compounds have excellent electron transfer and visible light absorption ability, demonstrating broad application prospects in the field of photocatalysis. In this work, the nitrogen vacancies (NVs) were successfully introduced into zinc porphyrin (ZnTCPP) ultrathin nanosheets through surface N2 plasma treatment, which is environmentally friendly and can react in low temperatures. Furthermore, the prepared nitrogen vacancies-zinc porphyrin (NVs-ZnTCPP) materials exhibited excellent photocatalytic CO2 reduction activity and selectivity, specifically, the CO production rate of ZnTCPP-1 (N2 plasma treatment, 1 min) achieved as high as 12.5 µmol g-1h-1, which is about 2.7 times greater than that of untreated ZnTCPP. Based on the experimental and density functional theory calculation (DFT) results, it is found that the promoted photocatalytic performance of NVs-ZnTCPP could be mainly attributed to nitrogen vacancy-induced spin polarization by reducing the reaction barriers and inhibiting the recombination of photoexcited carriers. This work provides a new perspective for the construction of vacancy-based metalloporphyrin, and further explores the intrinsic mechanism between the electron spin property and the performance of the photocatalyst.

Sodium-ion batteries (SIBs) are attracting worldwide attention due to their multiple merits including abundant reserve and safety. However, industrialization is challenged by the scarcity of high-performance carbon anodes with high specific capacities. Here, we report the metal-assisted microcrystalline structure regulation of carbon materials to achieve high-capacity sodium storage. Systematic investigations of in situ thermal-treatment X-ray diffraction and multiple spectroscopies uncover the regulation mechanism of constructing steric hindrance (C-O-C bonds) to restrain the aromatic polycondensation reaction. The carbon precursor of polycyclic aromatic hydrocarbon-type pitch contributes to a high carbon yield rate (40%) compared with those of resin and biomass precursors. The as-synthesized carbon materials deliver high capacities of up to 390 mAh g-1, surpassing many reported carbon anodes for SIBs. Through correlating specific capacity with ID/IG values in Raman spectra and theoretical calculation of carbon materials regulated by different metal elements (Mn, Nb, Ce, Cr, and V), we identify and propose the binding energy as the descriptor for characterizing the capability of regulating the carbon microcrystalline structure to promote sodium storage. This work provides a universal method for regulating the carbon structure, which may lead to the controlled design and fabrication of carbon materials for energy storage and conversion and beyond.

One of the biggest obstacles to the development of aqueous proton batteries (APBs), despite numerous optimization techniques, is the preparation and use of high-performance electrode materials. In this work, to improve the high solubility, limited capacity and poor cycle life of small organic molecules in APBs, homogeneous dispersed quinone-amine polymer nanospheres (PQANS) (average diameter: 220 nm) were synthesized by a polymerization reaction based on 3,3'-diaminobenzidine (DAB) and benzoquinone (BQ), making them suitable for proton storage in aqueous systems. As an anode for APBs, the obtained PQANS exhibits an improved reversible capacity of 126.2 mAh/g at 1 A/g after 300 cycles. The durable stable measurement of PQANS at 10 A/g was also conducted with a specific capacity of 66.8 mAh/g after 12,000 cycles. A series of in situ or ex situ measurements were used to establish the superior H+ storage mechanism of PQANS. A novel reaction mechanism of redox enhancement was revealed due to the existence of more carbonyl groups after the first cycle. Theoretical calculations were conducted to help illustrate the principle of binding protons with functional groups in PQANS. Finally, a PQANS anode-based aqueous proton full battery was constructed to demonstrate its potential application, which exhibits a specific capacity of 50.6 mAh/g at 1 A/g (600 cycles). This work provides a reference for preparing high-performance polymer-based electrode materials in aqueous batteries.

Compared with single-atom catalysts, clusters not only possess more metal-loadings and stability but also provide flexible active sites to break the linear scaling relationship of multistep reactions. However, exploring precise structure-activity relationships and the synergistic effect between clusters and nanosheets is still in its infancy. Here, based on first-principles and nonequilibrium Green's function simulation, the C2N-supported Fe and Co tetrahedral clusters exhibit remarkable bifunctional catalytic performance with a very low overpotential of hydrogen (0.12 and 0.07 V) /oxygen (0.20 and 0.55 V) evolution reactions (HER/OER), respectively. The C2N-regulated Fe and Co clusters have suitable d-band centers around the Fermi surface for HER. In turn, the Fe and Co clusters activate the subadjacent dual-carbon sites for OER. Simultaneously, the cluster enhances the electronic conductivity of C2N, and the initial current only needs ultralow bias voltage around 0.1-0.4 V. The desired metal cluster regulation strategy offers cost-effective potential for advancing clean energy technology.

The use of conductive MOFs (c-MOFs) in zinc-based batteries has been a popular research direction. Zinc-based batteries are widely used with the advantages of high specific capacity and safety and stability, but they also face many problems. c-MOFs have excellent conductivity compared with other primitive MOFs, and therefore have better applications in zinc-based batteries. In this paper, the transfer mechanisms of the unique charges of c-MOFs: hop transport and band transport, respectively, are discussed and the way of electron transport is further addressed. Then, the various ways to prepare c-MOFs are introduced, among which solvothermal, interfacial synthesis, and postprocessing methods are widely used. In addition, the applications of c-MOFs are discussed in terms of their role and performance in different types of zinc-based batteries. Finally, the current problems of c-MOFs and the prospects for their future development are presented.

The development of efficient and affordable electrode materials is crucial for clean energy storage systems, which are considered a promising strategy for addressing energy crises and environmental issues. Metal phosphorous chalcogenides (MPX3 ) are a fascinating class of two-dimensional materials with a tunable layered structure and high ion conductivity, making them particularly attractive for energy storage applications. This review article aims to comprehensively summarize the latest research progress on MPX3 materials, with a focus on their preparation methods and modulation strategies. Additionally, the diverse applications of these novel materials in alkali metal ion batteries, metal-air batteries, and all-solid-state batteries are highlighted. Finally, the challenges and opportunities of MPX3 materials are presented to inspire their better potential in energy storage applications. This review provides valuable insights into the promising future of MPX3 materials in clean energy storage systems.

Water splitting, an efficient technology to produce purified hydrogen, normally requires high cell voltage (>1.5 V), which restricts the application of single atoms electrocatalyst in water oxidation due to the inferior stability, especially in acidic environment. Substitution of anodic oxygen evolution reaction (OER) with hydrazine oxidation reaction (HzOR) effectually reduces the overall voltage. In this work, the utilization of iridium single atom (Ir-SA/NC) as robust hydrogen evolution reaction (HER) and HzOR electrocatalyst in 0.5 m H2 SO4 electrolyte is reported. Mass activity of Ir-SA/NC is as high as 37.02 A mgIr -1 at overpotential of 50 mV in HER catalysis, boosted by 127-time than Pt/C. Besides, Ir-SA/NC requires only 0.39 V versus RHE to attain 10 mA cm-2 in HzOR catalysis, dramatically lower than OER (1.5 V versus RHE); importantly, a superior stability is achieved in HzOR. Moreover, the mass activity at 0.5 V versus RHE is enhanced by 83-fold than Pt/C. The in situ Raman spectroscopy investigation suggests the HzOR pathway follows *N2 H4 →*2NH2 →*2NH→2N→*N2 →N2 for Ir-SA/NC. The hydrazine assisted water splitting demands only 0.39 V to drive, 1.25 V lower than acidic water splitting.

Water splitting is a promising technique in the sustainable "green hydrogen" generation to meet energy demands of modern society. Its industrial application is heavily dependent on the development of novel catalysts with high performance and low cost for hydrogen evolution reaction (HER). As a typical non-precious metal, cobalt-based catalysts have gained tremendous attention in recent years and shown a great prospect of commercialization. However, the complexity of the composition and structure of newly-developed Co-based catalysts make it urgent to comprehensively retrospect and summarize their advance and design strategies. Hence, in this review, the reaction mechanism of HER is first introduced and the possible role of the Co component during electrocatalysis is discussed. Then, various design strategies that could effectively enhance the intrinsic activity are summarized, including surface vacancy engineering, heteroatom doping, phase engineering, facet regulation, heterostructure construction, and the support effect. The recent progress of the advanced Co-based HER electrocatalysts is discussed, emphasizing that the application of the above design strategies can significantly improve performance by regulating the electronic structure and optimizing the binding energy to the crucial intermediates. At last, the prospects and challenges of Co-based catalysts are shown according to the viewpoint from fundamental explorations to industrial applications.

Nickel(II) porphyrins typically adopt a square planar coordination geometry, with the nickel atom located at the center of the porphyrin ring and the coordinating atoms arranged in a square plane. The additional atoms or groups coordinated to the nickel atom in nickel(II) porphyrins are called ligands. Porphyrins have been investigated as potential agents for imaging and treating cancer due to their ability to selectively bind to tumor cells and be used as sensors for a variety of analytes. Nickel(II) porphyrins are relatively stable compounds, with high thermal and chemical stability. They can be stored in a solid state or in solution without significant degradation. In this study, we compute several connectivity indices, such as general Randi'c, hyper Zagreb, and redefined Zagreb indices, based on the degrees of vertices of the chemical graph of nickel porphyrins. Then, we compute the entropy and heat of formation NiP production, among other physical parameters. Using MATLAB, we fit curves between various indices and the thermodynamic properties parameters, notably the heat of formation and entropy, using various linearity- and non-linearity-based approaches. The method's effectiveness is evaluated using [Formula: see text], the sum of squared errors, and root mean square error. We also provide visual representations of these indexes. These mathematical frameworks might offer a mechanism to investigate the thermodynamical characteristics of NiP's chemical structure under various circumstances, which will help us understand the connection between system dimensions and these metrics.

Conventional nitrogen vacancies with a symmetric coordination of metal cations (i.e., M1-Nv-M1) play a crucial role in tuning the local environment of the metal sites in metal nitrides and improving their electrochemical activity in the hydrogen evolution reaction (HER). However, the symmetric Nv sites, which feature a uniform charge distribution on adjacent metal sites, suffer from sluggish water dissociation kinetics and a poor capability for hydrogen desorption. Here, we fabricated Cr-doped and Nv-rich Co4N nanorods grown on a Ni foam (Cr-Co4N-Nv/NF) with asymmetric Cr-Nv-Co sites to effectively catalyze hydrogen evolution under alkaline conditions, with a low overpotential of 33 mV at a current density of 10 mA cm-2 and a small Tafel slope of 37 mV dec-1. The experimental characterizations and theoretical simulations collectively reveal that the construction of asymmetric Cr-Nv-Co sites gives rise to the upshift of the d-band center, thus promoting water adsorption and activation. Moreover, asymmetric Nv sites allow a balance between hydrogen adsorption and desorption, which avoids the limited desorption process over the symmetric Co-Nv-Co sites.

Proton exchange membrane water splitting (PEMWS) technology has high-level current density, high operating pressure, small electrolyzer-size, integrity, flexibility, and has good adaptability to the volatility of wind power and photovoltaics, but the development of both active and high stability of the anode electrocatalyst in acidic environment is still a huge challenge, which seriously hinders the promotion and application of PEMWS. In recent years, researchers have made tremendous attempts in the development of high-quality active anode electrocatalyst, and we summarize some of the research progress made by our group in the design and synthesis of PEMWS anode electrocatalysts with different nanostructures, and makes full use of electrocatalytic activity points to increase the inherent activity of Iridium (Ir) sites, and provides optimization strategies for the long-term non-decay of catalysts under high anode potential in acidic environments. At this stage, these research advances are expected to facilitate the research and technological progress of PEMWS, and providing some research ideas and references for future research on efficient and inexpensive PEMWS anode electrocatalysts.

Linear-conjugated polymers (LCPs) are excellent semiconductor photocatalysts. However, its inherent amorphous structures and simple electron transport channels restrict efficient photoexcited charge separation and transfer. Herein, "2D conjugated engineering" is employed to design high-crystalline polymer photocatalysts with multichannel charge transport by introducing alkoxyphenyl sidechains. The electronic state structure and electron transport pathways of the LCPs are investigated using experimental and theoretical calculations. Consequently, the 2D B←N-containing polymers (2DPBN) exhibit excellent photoelectric characteristics, which enable the efficient separation of electron-hole and rapidly transfer photogenerated carriers to the catalyst surface for efficient catalytic reactions. Significantly, the further hydrogen evolution of 2DPBN-4F heterostructures can be achieved by increasing the fluorine content of the backbones. This study highlights that the rational design of LCP photocatalysts is an effective strategy to spur further interest in photofunctional polymer material applications.

Developing highly active and robust oxygen catalysts is of great significance for the commercialization of Zn-air batteries (ZABs) with long-life stability. Herein, heterostructured catalysts comprising molybdenum carbide and metallic Co are prepared by a simple dicyandiamide-assisted pyrolysis strategy. Importantly, the crystalline phase of molybdenum carbide in the catalysts can be carefully regulated by adjusting the CoMo-imidazole precursor and dicyandiamide ratio. The electronic configuration of Co and Mo centers as well as the phase-dependent oxygen reduction reaction performance of these heterostructures (β-Mo2C/Co, β-Mo2C/η-MoC/Co, and η-MoC/Co) was disclosed. A highly active η-MoC/Co cathode enables ZABs with outstanding long-term stability over 850 h with a low voltage decaying rate of 0.06 mV·h-1 and high peak power density of 162 mW·cm-2. This work provides a new idea for the rational design of efficient and stable cathode catalysts for ZABs.

Coproporphyrin (CP)-I and CP-III are the markers of organic anion-transporting polypeptides' (OATPs) activities, and they are porphyrin metabolites that originate from heme synthesis. Furthermore, CP-I and CP-III, which are OATP1B endogenous metabolites, have gradually attracted the attention of scientists and researchers in recent years. Previous studies have also observed CP-I and CP-III levels as clinical biomarkers for predicting OATP1B inhibition in drug-drug interaction studies. To establish an accurate ultra-high performance liquid chromatography-mass spectrometry method for the quantitation of CP-I and CP-III, we reviewed previous methodological publications and applied them to a clinical pharmacology study using a human urine matrix. We used 13.25 M formic acid as a working solution for internal standards (CP-I 15N4 and CP-III d8) to avoid isobaric interference. The calibration curve showed good linearity in the range of 1-100 ng/mL, with a correlation coefficient (R2) higher than 0.996 in each validation batch. Both the between-run and within-run assays achieved good precision and accuracy, and we found that both CP-I and CP-III were stable in the pre-study validation. The method exhibited suitable dilution integrity, allowing for the re-analysis of samples with concentrations exceeding the upper limit of quantification through dilution. Overall, the application of the described method in a clinical study revealed that it can be utilized effectively to monitor drug-drug interactions mediated by OATP1B.

Ever-growing demands for rechargeable zinc-air batteries (ZABs) call for efficient bifunctional electrocatalysts. Among various electrocatalysts, single atom catalysts (SACs) have received increasing attention due to the merits of high atom utilization, structural tunability, and remarkable activity. Rational design of bifunctional SACs relies heavily on an in-depth understanding of reaction mechanisms, especially dynamic evolution under electrochemical conditions. This requires a systematic study in dynamic mechanisms to replace current trial and error modes. Herein, fundamental understanding of dynamic oxygen reduction reaction and oxygen evolution reaction mechanisms for SACs is first presented combining in situ and/or operando characterizations and theoretical calculations. By highlighting structure-performance relationships, rational regulation strategies are particularly proposed to facilitate the design of efficient bifunctional SACs. Furthermore, future perspectives and challenges are discussed. This review provides a thorough understanding of dynamic mechanisms and regulation strategies for bifunctional SACs, which are expected to pave the avenue for exploring optimum single atom bifunctional oxygen catalysts and effective ZABs.

The rise of flexible electronics calls for efficient microbatteries (MBs) with requirements in energy/power density, stability, and flexibility simultaneously. However, the ever-reported flexible MBs only display progress around certain aspects of energy loading, reaction rate, and electrochemical stability, and it remains challenging to develop a micro-power source with excellent comprehensive performance. Herein, a reconstructed hierarchical Ni-Co alloy microwire is designed to construct flexible Ni-Zn MB. Notably, the interwoven microwires network is directly formed during the synthesis process, and can be utilized as a potential microelectrode which well avoids the toxic additives and the tedious traditional powder process, thus greatly simplifying the manufacture of MB. Meanwhile, the hierarchical alloy microwire is composed of spiny nanostructures and highly active alloy sites, which contributes to deep reconstruction (≈100 nm). Benefiting from the dense self-assembled structure, the fabricated Ni-Zn MB obtained high volumetric/areal energy density (419.7 mWh cm-3 , 1.3 mWh cm-2 ), and ultrahigh rate performance extending the power density to 109.4 W cm-3 (328.3 mW cm-2 ). More surprisingly, the MB assembled by this inherently flexible microwire network is extremely resistant to bending/twisting. Therefore, this novel concept of excellent comprehensive micro-power source will greatly hold great implications for next-generation flexible electronics.

In this work, a new alkaline-stable boron imidazolate framework (BIF-90) was rationally designed and successfully synthesized by solvothermal reaction. Due to its potential electrocatalytic active sites (Co, B, N, and S) and chemical stabilities, BIF-90 was explored as a bifunctional electrocatalyst toward electrochemical oxygen reactions, namely, oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). This work will open new avenues toward the design of stable, cheap, and more active BIFs as bifunctional catalysts.

Exploring efficient, affordable and stable electrocatalyst toward hydrogen evolution reaction (HER) is of great scientific significance for the practical implementation of the water splitting. The heteroatom doping represents a serviceable strategy to further elevate the catalytic performance for a transition metal-based electrocatalyst because of the electronic regulation effect. Herein, a reliable self-sacrificial template-engaged approach is proposed to synthesize O-doped CoP (denoted as O-CoP) microflowers, which simultaneously considers the regualtion of electronic configuration via anion doping and sufficient exposure of active sites via nanostructure engineering. The suitable O incorporation content in CoP matrix could tremendously modify the electronic configuration, accelerate the charge transfer, promote the exposure of active sites, strengthen the electrical conductivity, and adjust the adsorption state of H*. Consequently, the optimized O-CoP microflowers with optimal O concentration display a remarkable HER property with a small overpotential of 125 mV to afford a current density of 10 mA cm-2 , a low Tafel slope of 68 mV dec-1 and long-term durability for 32 h under alkaline electrolyte, manifesting a considerable potential application for hydrogen production at large scale. The integration of anion incorporation and architecture engineering in this work will bring in a depth insight for the design of low-cost and effective electrocatalysts in energy conversion and storage systems.

Reduced CO2 emissions, conversion, and reuse are critical steps toward carbon peaking and carbon neutrality. Converting CO2 into high-value carbon-containing compounds or fuels may effectively address the energy shortage and environmental issues, which is consistent with the notion of sustainable development. Photocatalytic CO2 reduction processes have become one of the research focuses, where single-atom catalysts have demonstrated significant benefits owing to their excellent percentage of atom utilization. However, among the crucial challenges confronting contemporary research is the production of efficient, low-cost, and durable photocatalysts. In this paper, we offer a comprehensive overview of the study growth on single-atom catalysts for photocatalytic CO2 reduction reactions, describe several techniques for preparing single-atom catalysts, and discuss the advantages and disadvantages of single-atom catalysts and present the study findings of three single-atom photocatalysts with TiO2, g-C3N4 and MOFs materials as carriers based on the interaction between single atoms and carriers, and finally provide an outlook on the innovation of photocatalytic CO2 reduction reactions.

The urgent need to promote the development of sustainable energy conversion requires exploration of highly efficient oxygen evolution reaction (OER) electrocatalysts. Defect engineering is a promising approach to address the inherent low electrical conductivity of metal oxides and limited reaction sites, for use in clean air applications and as electrochemical energy-storage electrocatalysts. In this article, oxygen defects are introduced into La₂CoMnO_6-δ perovskite oxides through the A-site cation defect strategy. By tuning the content of the A-site cation, oxygen defect concentration and corresponding electrochemical OER performance have been greatly improved. As a result, the defective La_1.8CoMnO_6-δ (L_1.8CMO) catalyst exhibits exceptional OER activity with an overpotential of 350 mV at 10 mA cm^-2, approximately 120 mV lower than that of the pristine perovskite. This enhancement can be attributed to the increase in surface oxygen vacancies, optimized e_g occupation of transition metal at the B-site, and enlarged Brunauer-Emmett-Teller surface area. The reported strategy facilitates the development of novel defect-mediated perovskites in electrocatalysis.

In recent years, with pressing needs such as diabetes management, the detection of glucose in various substrates has attracted unprecedented interest from researchers in academia and industry. As a relatively new glucose sensor, non-enzymatic target detection has the characteristics of high sensitivity, good stability and simple manufacturing process. However, it is urgent to explore novel materials with low cost, high stability and excellent performance to modify electrodes. Metal-organic frameworks (MOFs) and their composites have the advantages of large surface area, high porosity and high catalytic efficiency, which can be utilized as excellent materials for electrode modification of non-enzymatic electrochemical glucose sensors. However, MOFs and their composites still face various challenges and difficulties that limit their further commercialization. This review introduces the applications and the challenges of MOFs and their composites in non-enzymatic electrochemical glucose sensors. Finally, an outlook on the development of MOFs and their composites is also presented.

In order to improve the electro-microstructural physiognomics of electrode materials for applications in better efficiency supercapacitors, herein graphitic carbon nitride (GCN)-heterostructurized CoS-NiCo₂S₄ is designed using a controlled material growth synthesis procedure. The developed CoS-NiCo₂S₄/GCN possesses ample hydrophilicity, possible charge transfer between GCN and CoS-NiCo₂S₄, uniform phase distribution, and distinctive microstructural characteristics. The preliminary electrochemical studies in the three-electrode setup show GCN-induced lower charge transfer resistance and very unique Warburg profile corresponding to extremely low diffusion resistance in CoS-NiCo₂S₄/GCN as compared to pristine CoS-NiCo₂S₄. Furthermore, GCN is found to significantly induce surface-controlled (capacitive-type) charge storage and frequency-independent specific capacitance up to 10 Hz in CoS-NiCo₂S₄. Furthermore, the CoS-NiCo₂S₄||N-rGO and CoS-NiCo₂S₄/GCN||N-rGO all-solid-state hybrid supercapacitor (ASSHSC) devices were fabricated using N-rGO as the negative electrode material, and the inducing effect of GCN on the supercapacitive charge storage performance of the devices is thoroughly studied. Results demonstrate that the mass specific capacitance and areal capacitance of CoS-NiCo₂S₄/GCN||N-rGO are ∼2 and ∼4 times more than those of the CoS-NiCo₂S₄||N-rGO ASSHSC device, respectively. Furthermore, the CoS-NiCo₂S₄/GCN||N-rGO offers more energy density, rate energy density, and additional charge-discharge durability (over ∼10,000 cycles) than the CoS-NiCo₂S₄||N-rGO ASSHSC device. The multifold performance improvement of CoS-NiCo₂S₄ with GCN heterostructurization is ascribed to GCN-induced supplemented porosity and pore widening, ionic nonstoichiometry (Ni^2±δ, Co^2±δ, and Co^3±δ), wettability, integrated enhancement in the conductivity, and electroactive-ion accessibility in the CoS-NiCo₂S₄/GCN heterocomposite. The present study offers vital physicoelectrochemical insights toward the future development of low cost and high-performance electrode materials, and their implementation in high-rate and operationally stable all-solid-state hybrid supercapacitor devices, for application in the next-generation front-line technologies.

Nickel-doped iridium echinus-like nanosheets (NiIr-ENS) have a superior acidic oxygen evolution reaction (OER) activity with a TOF of 1.72 s^-1 at an overpotential of 300 mV, 8.6-fold higher than that of IrO₂.

Porous carbon materials have demonstrated exceptional performance in various energy and environment-related applications. Recently, research on supercapacitors has been steadily increasing, and porous carbon materials have emerged as the most significant electrode material for supercapacitors. Nonetheless, the high cost and potential for environmental pollution associated with the preparation process of porous carbon materials remain significant issues. This paper presents an overview of common methods for preparing porous carbon materials, including the carbon-activation method, hard-templating method, soft-templating method, sacrificial-templating method, and self-templating method. Additionally, we also review several emerging methods for the preparation of porous carbon materials, such as copolymer pyrolysis, carbohydrate self-activation, and laser scribing. We then categorise porous carbons based on their pore sizes and the presence or absence of heteroatom doping. Finally, we provide an overview of recent applications of porous carbon materials as electrodes for supercapacitors.

The efficient CO₂ electroreduction into high-value products largely relies on the CO₂ adsorption/activation or electron-transfer of electrocatalysts, thus site-specific functionalization methods that enable boosted related interactions of electrocatalysts are much desired. Here, an oriented coordination strategy is reported to introduce N-rich auxiliary (i.e., hexamethylenetetramine, HMTA) into metalloporphyrin metal organic frameworks (MOFs) to synthesize a series of site-specific functionalized electrocatalysts (HMTA@MOF-545-M, M = Fe, Co, and Ni) and they are successfully applied in light-assisted CO₂ electroreduction. Noteworthy, thus-obtained HMTA@MOF-545-Co presents approximately two times enhanced CO₂ adsorption-enthalpy and electrochemical active surface-area with largely decreased impedance-value after modification, resulting in almost twice higher CO₂ electroreduction performance than its unmodified counterpart. Besides, its CO₂ electroreduction performance can be further improved under light-illumination and displays superior FE_CO (≈100%), high CO generation rate (≈5.11 mol m^-2  h^-1 at -1.1 V) and energy efficiency (≈70% at -0.7 V). Theoretical calculations verify that the oriented coordination of HMTA can increase the charge density of active sites, almost doubly enhance the CO₂ adsorption energy, and largely reduce the energy barrier of rate determining step for the boosted performance improvement. This work might promote the development of modifiable porous crystalline electrocatalysts in high-efficiency CO₂ electroreduction.

The realization of commercialization of proton electrolyte membrane water splitting technology significantly depends on the anodic electrocatalyst working at a high potential and strong acidic conditions requiring superior oxygen evolution reaction activity and stability. In this work, we devise the construction of ultrasmall Pd@Ir core-shell nanoparticles (5 nm) with atomic layer Ir (3 atomic layers) on carbon nanotubes (Pd@Ir/CNT) as an exceptional bifunctional electrocatalyst in acidic water splitting. Due to the core-shell structure, strain generated at heterointerfaces leads to an upshifted d band center of Ir atoms contributing to a 62-fold better mass activity at 1.63 V vs RHE than commercial IrO₂; besides, the electronic hybridization suppresses the electrochemical dissolution of Ir; as a result, robust stability is also achieved. In hydrogen evolution reaction catalysis, Pd@Ir/CNT exhibits a 3.7 times higher mass activity than Pt/C. Furthermore, only 1.7 V is required to reach a water splitting current density of 100 mA cm^-2, 251 mV lower than that of Pt/C-IrO₂, indicating its superiority in acidic water splitting.

The present research work facilitates a ligand-mediated effective strategy to achieve different morphological surface structures of bimetallic (Ni and Co) metal-organic frameworks (MOFs) by utilizing different types of organic ligands like terephthalic acid (BDC), 2-methylimidazole (2-Melm), and trimesic acid (BTC). Different morphological structures, rectangular-like nanosheets, petal-like nanosheets, and nanosheet-assembled flower-like spheres (NSFS) of NiCo MOFs, are confirmed from the structural characterization for ligands BDC, 2-Melm, and BTC, respectively. The basic characterization studies like scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller revealed that the NiCo MOF prepared by using trimesic acid as the ligand (NiCo MOF_BTC) with a long organic linker exhibits a three-dimensional architecture of NSFS that possesses higher surface area and pore dimensions, which enables better ion kinetics. Also, the NiCo MOF_BTC delivered the highest capacity of 1471.4 C g^-1 (and 408 mA h g^-1) at 1 A g^-1 current density, compared to the other prepared NiCo MOFs and already reported different NiCo MOF structures. High interaction of trimesic acid with the metal ions confirmed from ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy leads to a NSFS structure of NiCo MOF_BTC. For practical application, an asymmetric supercapacitor device (NiCo MOF_BTC//AC) is fabricated by taking NiCo MOF_BTC and activated carbon as the positive and negative electrode, respectively, where the PVA + KOH gel electrolyte serves as a separator as well as an electrolyte. The device delivered an outstanding energy density of 78.1 Wh kg^-1 at a power density of 750 W kg^-1 in an operating potential window of 1.5 V. In addition, it displays a long cycle life of 5000 cycles with only 12% decay of the initial specific capacitance. Therefore, these findings manifest the morphology control of MOFs by using different ligands and the mechanism behind the different morphologies that will provide an effective way to synthesize differently structured MOF materials for future energy-storage applications.

In the field of solid-state lithium metal batteries (SSLMBs), constructing vertically heterostructured poly(ethylene oxide) (PEO)-based solid electrolytes is an effective method to realize their tight contact with cathodes and Li anodes at the same time. Succinonitrile (SN) has been widely used in PEO-based solid electrolytes to improve the interface contact with cathodes, enhance the ionic conductivities, and obtain a high electrochemical stability window of PEO, but its application is still hindered by its intrinsic instability to Li anodes, which results in corrosion and side interactions with lithium metal. Herein, the cellulose membrane (CM) is introduced creatively into the vertically heterostructured PEO-based solid electrolytes to match the PEO-SN solid electrolytes at the cathode side. With the advantage of the interaction between -OH groups of CM and -C≡N groups in SN, the movement of free SN molecules from cathodes to Li anodes is limited effectively, resulting in a stable and durable SEI layer. In specific, the Li||LiFePO₄ battery with the CM-assisted vertically heterostructured PEO-based solid electrolyte by in situ preparation delivers a discharge capacity of around 130 mAh g^-1 after 300 cycles and capacity retention of 95% after 500 cycles at 0.5 C. Our work provides a solution to construct PEO-based solid electrolytes feasible to match cathodes and Li anodes effectively by intimate contact with electrodes.

Metal-organic frameworks (MOFs) have exhibited appreciable potential as catalytic agents in the field of material science. The research of new MOFs with dual functions in electrocatalysis and photocatalysis under ultraviolet (UV) irradiation is extremely pivotal for renewable energy applications. Hence, we synthesized a series of three-dimensional MOFs, namely, [Cd(bimb)₂(HITA)₂]_n (Cd-MOF 1), {[Cd(bimb)₆](NO₃)₂}_n (Cd-MOF 2), and [Cd(bimb)₄(ONO₂)₂]_n (Cd-MOF 3) (bimb = 1,4-bis(imidazol-1-ylmethyl)benzene; H₂ITA = 5-hydroxyisophthalic acid), with applicability in the oxygen evolution reaction process and Fenton-like photocatalysis. The obtained results show that Cd-MOF 1 exhibited the most remarkable catalytic performance, affording a current density of 10 mA cm^-2 at a very low overpotential of 279 mV and the smallest Tafel slope of 85.13 mV dec^-1. Meanwhile, these MOFs can generate hydroxyl radicals (•OH) under UV light irradiation with the existence of H₂O₂, enabling the rapid degradation of organic pollutants. This study provides a valuable direction for producing multifunctional and environmentally friendly catalysts.

The use of metal-organic frameworks (MOFs) in solid-state electrolytes (SSEs) has been a very attractive research area that has received widespread attention in the modern world. SSEs can be divided into different types, some of which can be combined with MOFs to improve the electrochemical performance of the batteries by taking advantage of the high surface area and high porosity of MOFs. However, it also faces many serious problems and challenges. In this review, different types of SSEs are classified and the changes in these electrolytes after the addition of MOFs are described. Afterward, these SSEs with MOFs attached are introduced for different types of battery applications and the effects of these SSEs combined with MOFs on the electrochemical performance of the cells are described. Finally, some challenges faced by MOFs materials in batteries applications are presented, then some solutions to the problems and development expectations of MOFs are given.

Since the discovery of graphene, research on the family of 2D materials has been a thriving field. Metal phosphorous chalcogenides (MPX₃ ) have attracted renewed attention due to their distinctive physical and chemical properties. The advantages of MPX₃ , such as tunable layered structures, unique electronic properties, thermodynamically appropriate band alignments and abundant catalytic active sites on the surface, make MPX₃ material great potential in electrocatalysis. In this review, the applications of MPX₃ electrocatalysts in recent years, including hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction, are summarized. Structural regulation, chemical doping and multi-material composite that are often effective and practical research methods to further optimize the catalytic properties of these materials, are introduced. Finally, the challenges and opportunities for electrocatalytic applications of MPX₃ materials are discussed. This report aims to advance future efforts to develop MPX₃ and related materials for electrocatalysis.

The oxygen reduction reaction (ORR) is a key process in green energy conversion technology. Heteroatom doping has been proven to be a prospective strategy to prepare metal-free carbon-based electrocatalysts, but such methods often suffer from uncontrollable catalyst frameworks and imprecise active sites. Herein, an organic heterocyclic strategy is adopted to modulate the charge redistribution of alkynyl-containing conjugated microporous polymers (CMPs) by introducing varied five-membered heterocyclic structures. Among these CMPs, the S, 2N-containing thiadiazole heterocyclic molecule (CMP-Tdz) with carbonized alginate materials (C_CA ) displays a remarkable quasi-four-electron-transfer ORR pathway, exhibiting an excellent half-wave potential (E_1/2 ) of 0.77 V, coupled with superior methanol tolerance and electrochemical stability, which are among the highest performance in the metal-free organic catalytic material systems. Density functional theory calculations prove that the high catalytic performance of these catalysts originates from the sp-hybridized C atom (site-2) which is activated by their adjacent heterocyclic structures. Importantly, the five-membered heterocyclic structures can also modulate the local charge distribution, and increase dipole moment, with significantly improved catalytic kinetics. This incorporation of chemically designed heterocyclic-containing alkynyl-CMPs provides a new approach to developing efficient metal-free carbon-based electrocatalysts for fuel cells.

Aqueous zinc-ion batteries (AZIBs) stand out among many monovalent/multivalent metal-ion batteries as promising new energy storage devices because of their good safety, low cost, and environmental friendliness. Nevertheless, there are still many great challenges to exploring new-type cathode materials that are suitable for Zn2+ intercalation. Vanadium-based compounds with various structures, large layer spacing, and different oxidation states are considered suitable cathode candidates for AZIBs. Herein, the research advances in vanadium-based compounds in recent years are systematically reviewed. The preparation methods, crystal structures, electrochemical performances, and energy storage mechanisms of vanadium-based compounds (e.g., vanadium phosphates, vanadium oxides, vanadates, vanadium sulfides, and vanadium nitrides) are mainly introduced. Finally, the limitations and development prospects of vanadium-based compounds are pointed out. Vanadium-based compounds as cathode materials for AZIBs are hoped to flourish in the coming years and attract more and more researchers' attention.

Photocatalytic overall water splitting with two-dimensional materials is a promising strategy to solve the problems of environmental pollution and energy shortage. However, conventional photocatalysts are often limited to a narrow visible photo-absorption range, low catalytic activity, and poor charge separation. Herein, given the intrinsic polarization facilitating the improvement of photogenerated carrier separation, we adopt a polarized g-C₃N₅ material combining the doping strategy to alleviate the abovementioned problems. Boron (B), as a Lewis acid, has a great chance to improve the capture and catalytic activity of water. By doping B into g-C₃N₅, the overpotential for the complicated four-electron process of the oxygen reduction reaction is only 0.50 V. Simultaneously, the B doping-induced impurity state effectively reduces the band gap and broadens the photo-absorption range. Moreover, with the increase of B doping concentration, the photo-absorption range and catalytic activity can be gradually improved. Whereas when the concentration exceeds 33.3%, the reduction potential of the conduction band edge will not meet the demand for hydrogen evolution. Therefore, excessive doping is not recommended in experiments. Our work affords not only a promising photocatalyst but also a practical design scheme by combining polarizing materials and the doping strategy for overall water splitting.

Beta-cyclodextrin (β-CD) stabilized cerium oxide nanoparticles (β-CD@CeO₂ NPs) were synthesized through a hydrothermal route. The electronic properties, surface functional group, surface composition, size, and morphologies of the as-synthesized β-CD@CeO₂ NPs were characterized using UV-visible spectroscopy, FTIR analysis, high resolution X-ray photoelectron spectroscopy (HRXPS), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The pH-dependent variation of the ζ-potential of β-CD@CeO₂ NPs and the catalytic activity of the NPs for the hydrolysis of paraoxon were investigated. The observed pseudo-first-order rate constant (k_obs) for the hydrolysis of paraoxon is increased with increasing pH and the ζ-potential of β-CD@CeO₂ NPs. The kinetics and mechanism of hydrolysis of paraoxon in the aqueous and cationic micellar media have been discussed.

The idealized urea electrocatalyst is crucial to boost the CN coupling reaction and simultaneously suppress their isolated reduction process after adsorbing N₂ and CO₂ molecules. Therefore, the dispersed MN₃ -M'N₄ moiety is investigated systematically, including 26 homonuclear and 650 heteronuclear di-metal systems. After, 205 stable systems are selected using lowest-energy principle and ab initio molecular dynamics simulations. According to three possible pathways, NCON, CO, and OCOH to produce urea, a five-step high-throughput screening method for excellent catalytic activity and a five-aspect high-throughput screening strategy for outstanding catalytic selectivity are proposed, respectively. The potential determined steps and the limiting potential through three pathways are identified. The data indicates both CO pathway and OCOH pathway are more competitive at lower Gibbs free energy. Significantly, the most favorite RuN₃ -CoN₄ combination possesses an extremely low limiting potential of -0.80 V for urea production, meanwhile it exists a strong foundation for experimental preparation. This work not only broadens electrocatalytic potentiality of developing di-metals as two active sites, but also provides a feasible high-throughput screening recipe for urea production.

Covalent organic frameworks (COFs) are excellent candidates for rationally designed metal-coordinated catalysts due to their porous structures and adjustable organic building blocks. In this work, a two-dimensional (2D) COF with novel fxt topology was synthesized. The newly devised COF had been fully characterized by a range of spectroscopic and microscopic techniques. The COF was further metallized by the gold species to form a heterogeneous catalyst that enabled the one-pot synthesis of flavone and its derivatives. The Au@COF catalyst showed high catalytic activity and good recyclability. This work demonstrates the great potential of metallized COFs with unique well-defined pores in organic catalysis.

The rational design of ingenious strategies to boost the intrinsic activity and stability of ruthenium (Ru) is of great importance for the substantial progression of water electrolysis technology. Based on Mott-Schottky effect, electronic regulation within a metal/semiconductor hybrid electrocatalyst represents a versatile strategy to boost the electrochemical performance. Herein, a typical Mott-Schottky hydrogen evolution reaction (HER) electrocatalyst composed of uniform ultrafine Ru nanoclusters in situ anchored on N-doped carbon nanofibers (abbreviated as Ru@N-CNFs hereafter) through a feasible and scalable "phenolic resin-bridged" strategy is reported. Both spectroscopy analyses and density functional theory calculations manifest that such rectifying contact can induce the spontaneous electron transfer from Ru to N-doped carbon nanofibers to generate a built-in electric field, thus enormously promoting the charge transfer efficiency and HER intrinsic activity. Moreover, the seamless immobilization of Ru nanoclusters on the substrate can prevent the active sites from unfavorable migration, coarsening, and detachment, rendering the excellent structural stability. Consequently, the well-designed Ru@N-CNFs afford prominent pH-universal HER performances with small overpotentials of 16 and 17 mV at 10 mA cm^-2 and low Tafel slopes of 31.8 and 28.5 mV dec^-1 in acidic and alkaline electrolytes, respectively, which are superior to the state-of-the-art commercial Pt/C and Ru/C benchmarks.

The construction of strong interactions and synergistic effects between small metal clusters and supports offers a great opportunity to achieve high-performance and cost-effective heterogeneous catalysis, however, studies on its applications in electrocatalysis are still insufficient. Herein, it is reported that W18 O49 nanowires supported sub-nanometric Ru clusters (denoted as Ru SNC/W18 O49 NWs) constitute an efficient bifunctional electrocatalyst for hydrogen evolution/oxidation reactions (HER and HOR) under acidic condition. Microstructural analyses, X-ray absorption spectroscopy, and density functional theory (DFT) calculations reveal that the Ru SNCs with an average RuRu coordination number of 4.9 are anchored to the W18 O49 NWs via RuOW bonds at the interface. The strong metal-support interaction leads to the electron-deficient state of Ru SNCs, which enables a modulated RuH strength. Furthermore, the unique proton transport capability of the W18 O49 also provides a potential migration channel for the reaction intermediates. These components collectively enable the remarkable performance of Ru SNC/W18 O49 NWs for hydrogen electrocatalysis with 2.5 times of exchange current density than that of carbon-supported Ru nanoparticles, and even rival the state-of-the-art Pt catalyst. This work provides a new prospect for the development of supported sub-nanometric metal clusters for efficient electrocatalysis.