Enhanced Local Electric Field for Efficient Water Splitting and Zn–Air Batteries Enabled by Ultrasmall CoNi-VN Derived from Polyoxovanadoborates

Enhancing local electric fields (LEFs) near catalytic centers is a pivotal strategy to elevate electrocatalytic efficiency by accelerating electron transport and ion enrichment. Herein, a high-performance nanocomposite multifunctional electrocatalyst with high-curvature nanostructures was designed to generate strong LEFs, addressing slow reaction kinetics and high thermodynamic barriers. Ultrasmall vanadium nitride (VN) and cobalt–nickel alloy (CoNi) nanocomposite electrocatalyst systems were constructed by incorporating polyethylenimine (PEI) as a soft template and polyoxometalates (POMs) as precursors. This approach effectively prevents nanoparticle agglomeration and enhances active site exposure. Finite-element simulations revealed that the ultrasmall CoNi-VN nanoparticles generated strong LEFs, significantly enhancing electron transport and ion concentration around active sites. Meanwhile, the integrated ultrahigh-specific surface area, heteroatom doping, and effective mass transfer of the carbon nanotube structure endowed CoNi/VN/BNCNT with excellent HER (η10, 109 mV), OER (η50, 362 mV), and ORR (E1/2, 0.85 V) activities. The rechargeable Zn–air batteries achieved a high specific capacity of 810 mAh g–1, a peak power density of 220 mW cm–2 at 350 mA cm–2, a high open-circuit voltage of 1.51 V, and a low charging/discharging voltage gap of 0.89 V. Moreover, CoNi/VN/BNCNT requires cell voltages of 1.52 and 1.67 V to achieve current densities of 10 and 50 mA cm–2 for water splitting. This work addresses the agglomeration of alloy and VN nanoparticles while regulating the intensity of the local electric field, providing a promising pathway for advanced energy conversion and storage technologies.增强催化中心附近的局部电场（local electric fields, LEFs）是通过加速电子传输与离子富集来提升电催化效率的关键策略。本文设计了一种具备高曲率纳米结构的高性能纳米复合多功能电催化剂以产生强局部电场，解决了反应动力学迟缓与热力学能垒过高的难题。通过以聚乙烯亚胺（polyethylenimine, PEI）作为软模板、多金属氧酸盐（polyoxometalates, POMs）作为前驱体，构建了超小尺寸氮化钒（vanadium nitride, VN）与钴镍合金（cobalt–nickel alloy, CoNi）组成的纳米复合电催化剂体系。该方法可有效抑制纳米粒子团聚并提升活性位点暴露率。有限元模拟结果显示，超小CoNi-VN纳米粒子可产生强局部电场，显著强化活性位点周围的电子传输与离子富集。与此同时，碳纳米管结构所兼具的超高比表面积、杂原子掺杂特性与高效传质能力，赋予CoNi/VN/BNCNT优异的析氢反应（hydrogen evolution reaction, HER，η₁₀=109 mV）、析氧反应（oxygen evolution reaction, OER，η₅₀=362 mV）与氧还原反应（oxygen reduction reaction, ORR，E₁/₂=0.85 V）催化活性。所制备的可充电锌空电池展现出810 mAh g⁻¹的高比容量、在350 mA cm⁻²下达到220 mW cm⁻²的峰值功率密度、1.51 V的高开路电压，以及0.89 V的低充放电电压差。此外，CoNi/VN/BNCNT用于水分解反应时，仅需1.52 V和1.67 V的电池电压即可分别达到10和50 mA cm⁻²的电流密度。本研究不仅解决了合金与VN纳米粒子的团聚问题，还实现了局部电场强度的精准调控，为先进能源转换与存储技术提供了极具前景的发展路径。