Anion exchange membranes for electrically rechargeable zinc–air batteries: Structure-transport-degradation relationships and design strategies

Eco-friendly electrolyte modification using neem leaf extract for enhanced aluminium–air battery performance

Advances in heterostructured and atomically dispersed metallic carbon catalysts for efficient oxygen reactions in zinc–air batteries

Fe single-atom catalysts with well-defined porous architectures and optimized Fe–Nx microenvironments show great potential for enhancing the oxygen reduction reaction. Herein, we report Fe–N5 single-atom catalysts, where each Fe atom coordinates with 4 pyridinic N and 1 axial pyrrolic N, for efficient oxygen reduction. A dual-confinement strategy, combining the wood framework with Fe3+ coordination, directs self-assembly of cellulose nanocrystals (CNCs) into a porous wood-derived architecture. Subsequent pyrolysis yields Fe–N5 catalysts anchored on N, S-codoped carbon with hollow, hierarchically interconnected 3-dimensional pores. Notably, coordination between CNCs and Fe3+ guides the formation of Fe–Nx moieties within a tailored microenvironment, enabling control over the coordination number, heteroatom doping, and the electronic structure. X-ray absorption spectroscopy and density functional theory calculations reveal that FeN5 moieties are optimized through 3 synergistic factors: Fe coordination with 4 pyridinic N and 1 axial pyrrolic N, S doping from residual sulfate ester groups in CNCs, and adjacent micropores. Collectively, these effects lower the *OH desorption barrier, accelerating the adsorption/desorption of oxygenated intermediates. Consequently, Fe–N5 single-atom catalysts exhibit an exceptional oxygen reduction reaction activity with a half-wave potential of 0.964 V. This dual-confinement strategy enables high-performance non-precious-metal catalysts for metal–air batteries, as evidenced by Fe–N5-based zinc–air batteries outperforming Pt/C.

The development of highly efficient, stable, and cost-effective non-precious metal electrocatalysts to replace conventional platinum-based materials holds profound significance for accelerating the commercialization of advanced energy conversion devices, such as zinc–air batteries (ZABs). Herein, we propose a facile and highly efficient strategy to prepare a defect-rich, highly active nitrogen-doped porous carbon-based electrocatalyst (denoted U-Fe-N-C, urea-assisted iron–nitrogen–carbon material), via high-temperature co-pyrolysis of heme with urea. Our results demonstrate that urea not only serves as an excellent nitrogen source during pyrolysis, introducing abundant topological defects and heteroatom doping sites, but also induces the carbon substrate to form a hierarchical sponge-like porous structure with a high specific surface area. This unique microenvironment effectively prevents the agglomeration of iron species at high temperatures, achieving enhanced dispersion of iron species stabilized within the nitrogen-rich carbon matrix. Electrochemical evaluations reveal that under the optimal synthesis conditions (a precursor mass ratio of 1:3, calcination at 900 °C), U-Fe-N-C exhibits excellent oxygen reduction reaction (ORR) catalytic performance, delivering a half-wave potential of 0.731 V vs. RHE, and shows long-term operational durability that significantly surpasses that of commercial Pt/C. Furthermore, liquid rechargeable zinc–air batteries assembled with U-Fe-N-C as the air cathode deliver remarkable cycling stability, operating for up to 270 h of charge–discharge cycling without noticeable performance degradation. This study not only provides useful insights into the mechanisms of pore formation and assistance but also offers a practical perspective for the rational design and scalable synthesis of high-performance metal–nitrogen–carbon (M-N-C) electrocatalysts.

The realization of solar-charging within rechargeable batteries has been a dream of several generations of scientists, marking a transformation in sustainable energy storage. The key challenge is that the photo-rechargeable electrodes need to simultaneously possess high photovoltaic efficiency and cycling stability. Herein, through dynamic reconfiguration of sp-hybridized carbon networks via direct photoexcitation, we present nitrogen-substituted graphdiyne as a metal-free photoelectrode for integrated solar-charging in rechargeable batteries. Nitrogen-substituted graphdiyne accelerates oxygen evolution reaction kinetics by the synergistic effect of improved intermediate adsorption and hole-mediated oxidation under light excitation. Nitrogen-substituted graphdiyne-based photo-coupled positive electrodes are applicable to multiple metal||air batteries (Zn||air, Li||O2, Mg||air, Fe||air, and Al||air), including a low charging voltage of 1.33 V and 96.9% energy efficiency in Zn||air batteries, along with stability over 230 cycles at 100 mA cm-2. The Li||O2 battery achieved an efficiency of 96.3%, while Mg||air, Fe||air, and Al||air systems exhibited reduced charging voltages. This research has pioneered a class of photoelectrodes whose active sites are directly and dynamically defined by light, opening avenues for high-efficiency solar-driven energy conversion and storage.

Design and engineering of gas–liquid–solid interfaces in rechargeable zinc–air batteries

Curcumin as a sustainable electrolyte additive for Zn–air batteries: Corrosion inhibition, interfacial dynamics, and enhanced discharge performance

Perovskite catalysts show great promise for the oxygen evolution reaction (OER) but still face challenges in activity and stability. Here, we report boron incorporation into Sr2(FeCo0.6Mo0.4)O5+δ to tailor the Co-O-Fe covalency and electronic states, delivering 300mV at 10mAcm- 2 and a 67mVdec- 1 Tafel slope with > 140h durability in 1m KOH. Spectroscopy shows lowered Co/Fe valences and an increased fraction of lattice oxygen, while Density Functional Theory(DFT) (ELF/DOS/free-energy) indicates strengthened Transition Metal-Oxygen (TM─O) bonding and reduced reaction barriers. These findings support a shift toward an adsorbate evolution like pathway with suppressed lattice oxygen participation, rationalizing both the enhanced activity and robustness. Flexible Zn air batteries using Sr2(FeCo0.6Mo0.4)0.9B0.1O5+δ exhibit lower charging overpotentials and superior cycling stability than Pt/C+RuO2, highlighting device relevance. This work establishes metalloid doping enabled covalency engineering as a general strategy to boost OER performance and stability in perovskites.

Superior Fe-doped α-MnO2 bifunctional catalyst for zinc–air batteries: comparative analysis of cycle stability and performance in transition metal-doped α-MnO2 systems

The main goal of this study was to develop and validate a laboratory-scale prototype of a rechargeable metal hydride (MH)–air battery integrating gas diffusion electrodes (GDEs) and MH electrodes with stable performance over extended operation (>500 h) and repeated charge–discharge cycling (>100 cycles). This work addresses the critical transition from optimized electrode materials to a functioning system by investigating its operation under deep-discharge conditions, a key but still insufficiently explored regime in the context of stationary renewable energy storage. In this respect, this study explicitly targets the practical applicability of the developed system rather than focusing solely on material-level performance. The most efficient electrode materials, previously optimized, were successfully integrated into a single-cell configuration and systematically evaluated under various operating conditions. By determining the limiting current density for stable GDE operation, an appropriate operating window was defined, enabling maximum capacity utilization without compromising electrode integrity. At a current density of 10 mA, the maximum depth of discharge was achieved at a cell voltage of 575 mV, ensuring operation in a regime that limits GDE degradation while maintaining high energy efficiency. In addition, the electrode retains its mechanical stability after operation is interrupted, indicating good structural robustness. Furthermore, the performance of two identical cells connected in series was investigated to assess system scalability. The cells were operated under near-limit conditions and exhibited stable behavior. Overall, the present results confirm that the developed MH–air battery system extends beyond laboratory-scale validation and shows strong potential for implementation in stationary energy storage applications.

Size-controlled synthesis of spinel nickel ferrite nanoparticles by electrochemical method for metal-air batteries

NiFeCo-PA@Mo2CTx hybrid catalyst for enhancing the oxygen evolution reaction and Zn–air battery performance through complete reconstruction

NiFeS4/Ni3S4/NiS multiphase sulfides integrated with carbon nanotubes for efficient and high-performance electrode in cobalt-free rechargeable zinc–air batteries: A demonstration of rare compounds by an interrupted chemical reaction

Electronically coupled FeMn dual-atom sites for demetallation-resistant and mechanism-tailored oxygen electrocatalysis toward rechargeable Zn–air batteries

Carboxylate-functionalized hydrogel electrolyte for ultralong-life flexible zinc–air batteries

Mechanistic insights into LYNF perovskite zinc–air battery

ABSTRACT The energy−efficient urea oxidation reaction (UOR), crucial for hydrogen production and environmental remediation, faces dual challenges of sluggish kinetics and competing oxygen evolution reaction (OER). To overcome these challenges, we construct a Ni 3 P/Ni 3 Mo 3 N heterostructure with a built−in electric field. Experimental and theoretical results collectively verify that pronounced electron transfer from Ni 3 P to Ni 3 Mo 3 N establishes a strong built−in electric field at the interface, creating distinct electron−deficient and electron‐rich regions. This field thus steers the oriented adsorption of urea molecules, with −NH 2 anchoring on Ni 3 P and C═O favoring Ni 3 Mo 3 N. This not only promotes urea activation and lowers the rate−determining step energy barrier but also enables efficient *COO desorption, ultimately overcoming the activity–stability compromise. Consequently, the catalyst delivers exceptional UOR performance, requiring only 1.46 V versus RHE to achieve 500 mA cm −2 , indicating superior UOR selectivity. In a urea−assisted water electrolyzer, the system operates at 1.72 V for 500 mA cm −2 , significantly outperforming conventional electrolysis (∼2.05 V), and exhibits robust stability over 450 h. Furthermore, the Zn−urea−air battery configuration demonstrates energy−efficient operation, excellent rechargeability, and electrochemical durability, highlighting its practical potential for energy storage. This work offers insights into built−in electric field−modulated UOR reaction pathways and provides a promising strategy for advanced energy‐saving catalysts.

ABSTRACT Lithium – air batteries (LABs) are a technology beyond lithium-ion batteries that have high energy density, but they can only operate in high-O2 atmosphere because of their low power output capability. The localized oxygen reduction reaction (ORR) clogs the porous air-electrode, prematurely stopping power generation in an air atmosphere that is ~21% O2. Here, we have developed a carbon nanotube (CNT)-based air-electrode combined with a carbon paper (CP) gas diffusion layer (GDL), denoted as CNT-with-CP. X-ray computed tomography (XCT) and mercury porosimetry reveal a hierarchical pore architecture between the CNT/CP layers. This architecture has a continuous pore distribution between the nanopores of the CNT layer and micrometer-sized CP voids, which is artificially supported inside the high porosity CP. This pore structure allows continuous O2 inhalation without the air-electrode pores being clogged, facilitating uniform ORR across the air-electrode under low-O2 gas atmosphere. This enables a fast discharge under an atmospheric O2 environment and extends the cycle life of LAB cells. Multiple stacks of CNT-with-CP air-electrodes and lithium foil anodes produced a lightweight Ah-class LAB with high energy density that operates under atmospheric O2. This battery had a discharge capacity of 1.6 Ah at a current of 0.10 A per a 5.2 g device, corresponding to an energy density of 740 Wh kg−1 at a power density of 48 W kg−1. This is the first study demonstrating a step toward ‘true’ LAB working with atmospheric O2 to provide a feasible power output in ambient air.

Highly dispersive and ultrasmall PdCu alloy anchored on PAA-grafted carbon nanotube as electrocatalysts for rechargeable zinc−air batteries