Synergistic interface engineering of FeNi-LDH/N-doped carbon hybrids for an ultra-low bifunctional voltage gap in zinc-air batteries.

Bifunctional electrocatalysts are pivotal in addressing the sluggish kinetics of the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in rechargeable zinc-air batteries. While carbon-based non-noble metal catalysts and transition metal hydroxides have demonstrated promising monofunctional catalytic performance in oxygen-related reaction processes, their integration into bifunctional catalysts with synergistic advantages, such as cost-effectiveness, extended cycle life, and high activity compared to commercial noble-metal benchmarks, remains scientifically challenging. Specifically, the rational design principles for achieving optimal bifunctionality and the underlying mechanism of component interactions require further elucidation. In this work, we develop low-loading FeNi layered double hydroxide (LDH) porous carbon composites (Fe/Ni-NC@LDH) via the hydrothermal method, achieving an ultralow bifunctional voltage gap (ΔE = 0.649 V). The assembled zinc-air battery demonstrates outstanding durability with 300 cycles at 10 mA cm-2, retaining 53.8% voltage efficiency after 100 hours of continuous operation, significantly outperforming Pt/C + IrO2 counterparts, which suffered from severe polarization in less than 10 hours. Combined XPS characterization and DFT calculations indicate that hydrothermal FeNi-LDH deposition modifies the surface coordination environment and the local electronic structure of the carbon-based matrix, providing a plausible interfacial origin for the improved bifunctional electrocatalytic behavior. Remarkably, the designed catalyst not only preserves the inherent ORR advantages of carbon-supported non-precious metal systems but also substantially boosts OER capability, resulting in significantly improved charge-discharge durability. This interfacial engineering strategy provides fundamental insights for developing advanced non-noble metal bifunctional electrocatalysts toward next-generation metal-air battery technologies.