Hydrogen energy is recognized as an important renewable energy source with zero carbon emission. Hydrogen production via water splitting is considered to be one of the most promising technologies in the future hydrogen economy. The critical challenge facing this technology is to explore low-cost, efficient, and stable electrocatalysts. As one of the most promising materials in the twenty-first century, metal oxides have attracted extensive attention from researchers all over the world because of their excellent physical and chemical properties. However, before 2015, the performance of metal oxides in hydrogen evolution reaction (HER) was not satisfactory. It is encouraging that in recent years, with the continuous breakthrough of researchers in the study of metal oxide, it has gradually become one of the most potential HER electrocatalytic materials. In this chapter, we mainly present the recent progresses made by metal oxides in electrocatalytic HER, and the related challenges and future prospects are proposed.

High-voltage phosphate cathodes are a kind of promising electrode materials for constructing high-energy density sodium-ion batteries (SIBs). However, as a typical representative, Na4Co3(PO4)2P2O7 (NCPP), which commonly suffers from inevitably complicated structural evolution and sluggish kinetics resulting in generally unsatisfactory rate and cycling performance, which severely hinders its practical applications as ultra highvoltage cathode materials. Herein, Na4Co2Fe(PO4)2P2O7 (NCFPP) is designed to optimize the Co2+/Co3+ redox reaction, enabling a highly reversible single-phase transformation mechanism that displays enhanced rate capability and cycling stability. Furthermore, an entropy-regulation strategy is proposed to further strengthen the structural stability by suppressing undesirable topotactic phase transition. As a result, the designed mediumentropy cathode, Na3.7Co1.5Fe0.75(MgAlCuZn)0.2(PO4)2P2O7 (ME-NCFPP), delivers remarkably ultra-long cycling stability (80.3% capacity retention after 10,000 cycles at 10 C) and excellent two-year storage performance, far surpassing the NCFPP electrode. Additionally, the ME-NCFPP||hard carbon (HC) full cell displays excellent cycling stability. The underlying sodium-storage mechanism of the ME-NCFPP electrode is systematically unraveled through theoretical calculations combined with advanced characterization techniques, including in situ X-ray diffraction and synchrotron-based X-ray absorption spectroscopy. This work highlights the critical role of entropy engineering in suppressing multi-phase transitions, paving the way for constructing highly stable high-voltage cathodes for SIBs.

Fuel cell hybrid electric vehicles (FCHEVs) offer zero emissions, high efficiency, and fast refueling, but the slow response of proton exchange membrane fuel cells (PEMFCs) necessitates hybridization with secondary energy storage for transient power. Effective energy management is challenged by lacking real time information on key internal physicochemical states. To bridge this gap, we develop a cross scale powertrain model that links PEMFC electrochemical and mass transport mechanisms with vehicle dynamics and driver behavior, allowing real time tracking of internal stack states such as reactants concentrations, membrane water content, and catalyst layer degradation process. On the basis of this modeling platform, we propose a degradation-aware energy management strategy (DEMS) that dynamically adjusts PEMFC output according to catalyst layer states, including electrochemically active surface area, liquid water saturation ratio, and oxygen concentration. Simulations using operational data from fuel cell demonstrate that DEMS suppresses voltage drops by 3.45 % at the end of life, reduces reactant starvation, and maintains better membrane hydration than conventional strategies. System efficiency improves by 7.08 % across typical driving cycles. These results show that incorporating internal state observability and degradation dynamics into modeling and control markedly enhances FCHEV performance and durability in real world application.

Interfacial charge-transfer kinetics and the stability of Al deposition/stripping constitute pivotal determinants governing the long-term cyclability of rechargeable aluminum-ion batteries. Given the substantial challenges in regenerating the metallic Al produced...

Aqueous aluminum-ion batteries represent a promising energy storage technology, leveraging their exceptional capacity, low cost, and inherent safety. However, their practical implementation has been hampered by severe performance degradation at subzero temperatures and a scarcity of cathode materials with high capacity. Here, we present a conjugated bipolar polymer poly(2,3-diaminonaphthalene-1,4-dione) (PDND) synthesized via continuous-flow organic electrosynthesis. This molecular design incorporates a quinone-amine redox system that unifies n-type (quinone) and p-type (amine) moieties, thereby enhancing charge storage capacity. The extended quinone-amine backbone enhances p-pi conjugation, enabling efficient pi-electron delocalization and continuous charge transport pathways along the polymer chain, resulting in high electronic conductivity. Furthermore, the planar pi-conjugated quinone units and arylamine linkages construct synergistic dual-interaction networks between the polymer chains, including dense hydrogen-bonding and strong pi-pi interaction, ensuring structural stability. Consequently, the Al//PDND battery delivers a high capacity of 302 mAh g-1, outstanding cycling stability (>= 1000 cycles), and remarkable rate capability (up to 2 A g-1). Notably, it operates effectively at -25 degrees C using a standard aqueous electrolyte without antifreeze additives, underscoring the superior low-temperature performance endowed by PDND. Through in situ/ex situ spectroscopic studies, we elucidate a multi-ion co-storage mechanism involving the reversible insertion of Al3+, H+, and ClO4- ions.

Aqueous multivalent Zn- and Al-ion batteries offer intrinsic safety and high theoretical capacities, yet the high charge density of Zn2+ and Al3+ leads to sluggish kinetics and structural instability in inorganic intercalation cathodes. Organic cathodes present a promising alternative due to their coordination-driven redox chemistry, yet the practical deployment is limited by the high solubility of small molecules. Conventional strategies like polymerization and hybridization fail to balance stability, redox activity, and energy density. Here, we adopt an intrinsic small-molecule design strategy and develop a quinone-based small molecule, NQNT, that integrates adjacent carbonyl (C & boxH;O) and imine (C & boxH;N) groups within a rigid conjugated backbone to maximize redox-site accessibility, suppress dissolution, and enable stable multivalent-ion coordination. As a result, Zn//NQNT delivers a high capacity of 235 mAh g(-1), a similar to 0.8 V discharge plateau, excellent rate capability, and ultrastable cycling over 50 000 cycles. Operando and ex situ spectroscopy reveal a highly reversible six-electron Zn2+/H+ co-storage mechanism. NQNT also exhibits efficient Al3+ storage (212 mAh g-1) and robust performance from -50 degrees C to 50 degrees C. This work establishes a generalizable molecular-design strategy for stable, high-energy organic cathodes compatible with diverse multivalent-ion chemistries.

The selective coupling between *CHO and *OH intermediates is critical for mitigating catalyst poisoning during the methanol oxidation reaction (MOR). However, achieving such selective coupling on Pt-based catalysts with atomic precision remains a grand challenge. Herein, we report an orthorhombic intermetallic Pt5Ga3 catalyst with a precisely defined atomic arrangement, in which the spatial organization of surface Pt atoms provides an optimal geometric separation that suppresses *CHO dehydrogenation and redirects MOR toward a CO-free pathway. Pt5Ga3/C delivers a peak mass activity of 1.88 A mgPGM(-1), over four times that of commercial Pt/C. Combined H-1 NMR and in situ Raman spectroscopy demonstrate that the multifold Pt ensembles on Pt5Ga3 favor a CO-free MOR pathway. Complementary density functional theory (DFT) calculations further reveal that the conventional CO-poisoning pathway is significantly inhibited on Pt5Ga3, whereas the HCOOH-mediated pathway proceeds with a lower activation barrier. Further incorporation of oxophilic metals (Rh, Ru, Pd) affords Pt4MGa3 derivatives with enhanced OH adsorption. Among them, Pt4PdGa3/C exhibits the best MOR performance, delivering nearly twice the mass activity of Pt5Ga3/C. This work establishes Pt5Ga3 as a platform for steering MOR through a CO-free route and offers a structure- and composition-guided strategy for developing CO-tolerant electrocatalysts.

Aqueous zinc metal batteries are promising for energy storage, yet their application is constrained by the thermodynamic instability of Zn anodes. A deep understanding of interfacial evolution including initial nucleation and dendrite growth is crucial to guide electrochemical performance optimization, while real-time characterization remains a major technical hurdle. Herein, a homemade Cr-modified zinc foil (Zn@Cr) is designed as the working electrode for in situ electrochemical atomic force microscopy (AFM), enabling real-time visualization of initial nucleation and subsequent plating/stripping morphology evolution from the nano- to micrometer scale. The zincophilic Cr coating promotes uniform nucleation and forms a ZnCr interphase via in situ alloying at the early stage of electrodeposition, which functions as a physical barrier against electrolyte corrosion and preserves structural integrity during cycling. Consequently, Zn@Cr symmetric cells deliver ultralow nucleation overpotential and prolonged cycling stability, completely free of Zn dendrites. This work not only demonstrates an effective alloying-based interfacial strategy for stabilizing zinc anodes but also highlights the capability of in situ AFM in revealing dynamic interfacial evolution.

Low room-temperature conductivity, narrow electrochemical stability window, and insufficient mechanical strength restrict the further application of solid polymer electrolytes in solid-state sodium metal batteries (SMBs). Here, we reported a 50 & micro;m-thick fiber-reinforced fluorinated polymer plastic crystal electrolyte (PPCE) prepared via in-situ polymerization. The fluorinated polymer effectively disrupts the ordered structure of the plastic crystal, thus increasing the proportion of amorphous phase that provides rapid Na+ transport pathways. Meanwhile, the fluorohydrocarbon and ether units within polymer weaken its binding energy with Na+, which facilitates Na+ dissociation and achieves high room-temperature conductivity (2.34 mS cm- 1). Furthermore, the fluorine-rich groups enhance PPCE's oxidation resistance and deliver a robust, inorganic F-rich interphase, which stabilize the electrode/electrolyte interface and extend high-voltage tolerance (4.83 V). The integration of a 34 & micro;m-thick polyethylene fiber-reinforced substrate (tensile strength: 8.50 MPa) and the copolymer skeleton provides critical mechanical support. When paired with various cathodes, including Na3V4(PO4)3, Prussian white, Na3V2(PO4)2F3, or NaNi0.33Fe0.33Mn0.33O2, the cells deliver high capacity, stable cyclability, and excellent rate performance. This work demonstrates a highly compatible and robust PPCE design, highlighting its broad application prospects in advanced solid-state sodium batteries.

Organic materials are promising candidates as cathodes for high-performance aqueous Zn-ion batteries (AZIBs) owing to their high capacity, structural adjustability, and sustainability. However, their practical application is hindered by limited redox activity and low electronic conductivity under harsh operating conditions. Here, we report an organic polymer cathode prepared using a simple one-pot method, poly(mellitic trianhydride-phenazine) (PMPZ), featuring a fully conjugated structure and abundant active functional groups. The incorporation of heterocyclic conjugated units into the conjugated polymer structure enhances its electron affinity and p-electron delocalization, resulting in high redox activity and significantly elevated conductivity. Meanwhile, multiple C=O and C=N redox-active centers act cooperatively to enable a multielectron redox process through this delocalization pathway, thereby improving charge storage and reaction kinetics. Through combined theoretical and operando synchrotron experimental studies, we further elucidate that this fully conjugated structure facilitates reversible Zn2+/H+ co-storage with multiple electron transfers. Consequently, the PMPZ cathode demonstrates exceptional electrochemical performance with remarkable rate capability and outstanding cycling stability across a wide temperature range from-50 degrees C to 50 degrees C, even with seawater-based electrolytes. This work provides a novel design strategy for developing high-performance AZIB cathodes capable of operating under extreme conditions.

Four-electron aqueous Zn-iodine batteries (4eZIBs) can, in principle, double the iodine-based capacity of conventional two-electron Zn-I2 cells via sequential I-/I2/I+ redox chemistry. Their practical operation, however, is plagued by an inherent water-activity dilemma: sufficient water guarantees fast ion transport, whereas reactive free water accelerates I+ hydrolysis, polyiodide shuttling, Zn corrosion, hydrogen evolution, and dendritic Zn deposition. Here, we report a water-content-regulated hydrated eutectic electrolyte, denoted EMIC-1260, formulated from ZnSO4·7H2O, 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl), and an optimized amount of water. The sulfate/chloride-rich eutectic ion–dipole network reorganizes the hydrogen-bonding environment and Zn2+ solvation sheath, lowering water activity without compromising interfacial ion transport. This electrolyte reduces the Zn2+ desolvation barrier, suppresses water-induced parasitic reactions, and enables uniform Zn deposition. On the iodine cathode, the chloride-rich environment promotes reversible ICl-mediated I2/I+ conversion, while the tuned water environment mitigates hydrolysis and restrains I3- accumulation. As a result, Zn||Zn cells cycle stably for 10000 h, Zn||Cu cells deliver an average Coulombic efficiency of 99.77% over approximately 2400 cycles, and Zn||I2 full cells sustain stable operation for more than 40000 cycles at 10 C with a retained capacity of 138.03 mAh g-1. This work establishes water-activity regulation in hydrated eutectic electrolytes as a reliable chemical design principle for constructing high-rate and long-life 4eZIBs.

Achieving high activity and stability while reducing Pt loading remains a major challenge in developing cathode oxygen reduction reaction (ORR) catalysts for H2/air fuel cell. Here, a novel low-Pt intermetallic nitride catalyst (PtFe3N) consisting of a strained Pt shell and an antiperovskite-type PtFe3N core on a confinement-effect carbon support are synthesized via an initial impregnation-co-reduction strategy. The MEA with PtFe3N/DMC as cathode yields a current density of 1370 mA cm-2 at 0.6 V and maximum power density of 0.92 W cm-2, significantly outperforming that of Pt/C benchmark (1170 mA cm-2 and 0.79 W cm-2). Besides, the PtFe3N/DMC enabled MEA has a lower performance decay rate (1.9%) compared to the MEA with Pt/C (48.2%). EXAFS, XPS and DFT calculations jointly support that the cooperative strain effects induced by Fe and N endows PtFe3N with an optimal Pt d-band center position and accelerated kinetics. Furthermore, the introduction of N elements promoted the strong metal-N interactions, which effectively suppress Fe dissolution and significantly improve the ORR durability under operating conditions. This work provides a novel strategy for low-Pt intermetallic to enhance the corrosion resistance of 3d transition metals and to improve the ORR activity.

Low-platinum (low-Pt) alloys are widely regarded as a promising alternative to commercial Pt/C catalysts, owing to their excellent balance of cost reduction and enhanced catalytic performance. However, they have long been hindered by a critical challenge-poor durability-primarily stemming from the dissolution of non-noble metals. Herein, we report a series of high-performance, stable low-Pt high-entropy intermetallic catalysts with the composition Pt(FeCoNi)3-xInx (where x = 0.25, 0.5, 0.75, 1), and systematically elucidate the role of entropy in regulating both the dissolution behavior of non-noble metals and the overall catalytic performance. The optimized high-entropy intermetallic Pt(FeCoNi)2.5In0.5 (PFCNI) exhibited significantly superior stability to its binary counterparts. PFCNI delivered an initial mass activity of 1.04 A mgPt-1, with only a 14.3% loss after 30 000 accelerated durability test (ADT) cycles-outperforming both commercial Pt/C and the binary reference catalysts. When integrated into a membrane electrode assembly (MEA), PFCNI retained 74.1% of its maximum power density after 30 000 accelerated stress test (AST) cycles. In contrast, the MEA based on PtNi3 (a binary counterpart) retained merely 16.8% of its maximum power density even after a shorter duration of 20 000 AST cycles. This study demonstrates that the high-entropy effect remarkably enhances the stability of typical PtM3-type catalysts for the acidic oxygen reduction reaction (ORR), thereby offering a promising strategy for the development of low-Pt catalysts with long-term durability.

Ruthenium (Ru) is a promising alternative to platinum for hydrogen oxidation (HOR) and evolution (HER), yet its intrinsically strong hydrogen binding, governed by its atomic geometry, limits activity. Herein, we report a highly efficient and durable RuGa intermetallic catalyst with an atomically ordered structure that disrupts the geometric symmetry of Ru, thereby optimizing hydrogen adsorption. The catalyst achieves a specific exchange current density of 1.02 mA cm- 2 and a mass activity of 1850 mA mgRu - 1 for HOR, 5.5- and 3-fold higher than Ru/C, respectively. For HER, it requires only 11 mV to reach 10 mA cm- 2 and shows a 7.4-fold higher mass activity than Ru/C. Remarkably, it exhibits negligible degradation after 1000 HOR and 10 000 HER cycles. Density functional theory calculations and in situ Raman analyses reveal that geometric engineering enhances Ru 4d-H 1s hybridization, weakens Ru-H bonding, and lowers hydrogen adsorption energy, thus accelerating HER/HOR kinetics and preventing active-site poisoning. This work establishes a paradigm for designing high-performance Ru-based electrocatalysts through atomic-level geometric modulation.

The large-scale multiscenario application of sodium-ion batteries (SIBs) remains constrained by critical challenges, such as suboptimal fast-charging performance and poor temperature adaptability. The ideal electrolyte must simultaneously possess intrinsic nonflammability, rapid charge-transfer kinetics, and robust interphases, yet balancing these key parameters poses significant challenges. Herein, a multifunctional cosolvent (ethoxy(pentafluoro) cyclotriphosphazene, PFPN), featuring weak coordination capability, F/N/P-rich, and nonflammable characteristics, is employed to revolutionize the carbonate electrolyte. The weak coordination ability of PFPN creates an anion-reinforced solvation chemistry, greatly enhancing the charge-transfer kinetics. Meanwhile, the F/N/P-rich characteristic of PFPN and the unique anion-reinforced solvation chemistry facilitate the construction of robust, inorganic-rich electrode/electrolyte interfaces, effectively preventing continuous electrolyte decomposition and the dissolution of transition metals. Furthermore, PFPN endows the electrolyte with a wide electrochemical window and inherent nonflammable properties. As a result, the Prussian blue parallel to hard carbon (PB parallel to HC) full cell demonstrates favorable fast-charging performance (with a capacity retention of up to 72.5% after 600 cycles at 3.0 C) and temperature adaptability (-20 to 80 degrees C). Furthermore, 18650-type cylindrical cells and Ah-level PB parallel to HC pouch cells deliver reliable electrochemical performance, indicating the practical viability of the designed electrolyte for SIBs across diverse operating scenarios.

Four-electron aqueous zinc-iodine batteries (4eZIBs) offer high energy density but suffer from irreversible I+ hydrolysis, polyiodide shuttling, poor zinc anode stability, and a limited operating temperature range. Here, we propose a coordination competition and hydrogen-bond reconstruction strategy using a hybrid electrolyte of Zn(ClO4)2·6H2O, ZnCl2, InCl3, and polyethylene glycol 400 (PEG400), which enables reversible I+/I2/I- conversion for large-capacity Zn‖I2 batteries over a wide temperature range. Specifically, In3+ ions suppress polyiodide formation through preferential coordination with I- and electrostatic shielding that blocks charge exchange between I- and I2, and they are also preferentially reduced to metallic indium on the zinc anode surface, forming a protective indium layer that inhibits hydrogen evolution and corrosion. Meanwhile, PEG400 reduces the activity of free water by reconstructing the hydrogen-bond network of water molecules, and its polar segments can confine the ICl intermediate to suppress I+ hydrolysis. This synergistic chemistry enables an ultra-long Zn anode lifespan (over 4000 h), excellent Zn‖I2 full cell stability (over 10 000 cycles), record wide-temperature operation (-50 °C to 70 °C), and scalable Ah-level pouch-cell stability. This work provides a robust strategy for simultaneously managing complex interhalogen chemistries and stabilizing the zinc anode, paving the way toward practical aqueous energy storage.

Sodium-ion batteries (SIBs) are promising for large-scale energy storage due to the natural abundance and low cost of sodium. Hard carbon (HC) derived from coal tar pitch (CTP) is a competitive candidate, but its limited interlayer spacing and undeveloped pore structure restrict sodium storage capacity and rate performance. Herein, we demonstrate an Fe species-catalyzed strategy to precisely regulate the microstructure of CTP-derived HC. During carbonization, Fe3+ ions coordinate with oxygen-containing functional groups of oxidized CTP, ensuring molecular-level dispersion, and are sequentially reduced to form uniformly encapsulated Fe3C nanoparticles (∼4.9 nm). The resulting Fe3C species play a dual catalytic role: they promote localized graphitization to enhance electrical conductivity, while simultaneously regulating carbon ordering to preserve an expanded interlayer spacing (d002 = 0.391 nm) and promote closed-pore formation, as confirmed by SAXS and HRTEM analyses. The modified HC-Fe0.5 exhibits a reversible capacity of 409 mA h g−1 at 0.03 A g−1 and demonstrates excellent rate performance from 0.03 to 2.0 A g−1. The strategy in this work provides a catalytic regulation route of stable HC microstructure, for the utilization of coal-based materials in the field of energy storage.

The stabilization of Ru-based materials for acid oxygen evolution reaction (OER) is critical to developing efficient and cost-effective proton exchange membrane water electrolyzers (PEMWE). However, inhibiting Ru dissolution caused by overoxidation under operating conditions remains a major challenge. Here, we manipulate the octahedral Ru-O covalency in a Ru-Bi pyrochlore framework to reinforce the Ru-O bond, achieving highly stabilized and efficient OER in acid. By partially substituting Ru sites with Mn, we rationally tune the band alignment of O 2p and Ru 4d orbitals, reducing their overlap and thereby increasing the energy barrier for Ru dissolution. Moreover, Mn incorporation induces a reconstructed interfacial water structure to boost OER kinetics. The resulting Mn-RuBiO catalyst exhibits ultrastable OER performance at 100 mA cm- 2 over 2200 h, with a superhigh stability number of 9446,000, and demonstrates favorable durability in a PEMWE for over 550 h. Additionally, Mn-RuBiO achieves a 25-fold increase in mass activity and a 34-fold increase in specific activity, requiring only 213 mV at 10 mA cm- 2 and enabling a low cell voltage of 1.63 V at 1 A cm- 2 on PEMWE. This work presents a practical strategy to stabilize Ru species, enabling durable and high-performance PEMWE catalysts.

Aqueous four-electron zinc-iodine batteries (4eZIBs) hold great promise for long-term energy storage, but their practical application is severely hindered by the multiple drawbacks, including Zn dendrite growth, polyiodide shuttle, and I+ hydrolysis. Such limitations can be effectively mitigated by employing biphasic electrolytes featuring a liquid-liquid interface, which enables efficient immobilization of the dissolved reaction intermediates. However, such systems frequently employ toxic organic solvents, which not only pose flammability risks but also struggle to adapt to extreme temperature conditions. Herein, we design a novel self-stratified biphasic electrolyte via liquid-liquid phase separation of choline chloride (ChCl)-trifluoroacetamide (TFA) deep eutectic solvent (DES) and ZnSO4/H2O/ ethylene glycol solution. The upper DES phase effectively confines polyiodide anions, suppresses shuttle effect and stabilizes I+ species, while the bottom aqueous phase regulates Zn2+ solvation structure and inhibits dendrite formation and side reactions. Benefiting from the synergistic functional separation, the Zn-I2 battery realizes highly reversible four-electron conversion, effectively suppresses battery self-discharge, and delivers superior cycling stability over 21000 cycles as well as wide temperature tolerance ranging from -30°C to 50°C. This work offers novel insights into the design of safe and eco-friendly biphasic electrolytes and provides an effective strategy for the construction of high-performance 4eZIBs.

Interfacial hydrogen bond connectivity (HBC) of electrical double layer (EDL) has been identified as a critical factor for many electrocatalytic reactions, However, there is a lack of systematic investigation on the correlation between HBC and oxygen evolution reaction (OER) kinetics, and the advanced strategies to rationally manipulate HBC. Herein, we proposed an interfacial charge manipulation (ICM) methodology to engineer HBC and enhance OER kinetic of various electrocatalysts including Ni3FeN and the benchmark oxides (RuO2, Ni(OH)2, Co(OH)2, FeNi LDH, and FeCo LDH). With Ni3FeN as a model catalyst, we systematically studied the influence of different anion chemisorption (NO3-, SO42-, and PO43-) on HBC and establishing a positive correlation between OER activity and the charge of anions. Electrochemical tests show that the modified Ni3FeN catalysts with NO3-, SO42-, and PO43-exhibit 1.1-, 1.4-, and 2.3-fold activity enhancements at 1.5-1.6 V vs. RHE relative to the raw Ni3FeN, respectively. The in-situ spectroscopy and AIMD reveal that high anion charges increase four-hydrogen-bonded water populations, strengthening HBC to promote proton transfer across the EDL during deprotonations step and lower energy obstacle of the rate-determining step. This work has offered a new paradigm to regulate the interfacial HBC at molecular scale for promoting OER. (c) 2026, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.