Trifunctional robust electrocatalysts based on 3D Fe/N‐doped carbon nanocubes encapsulating Co₄N nanoparticles for efficient battery‐powered water electrolyzers

Abstract Herein, we have designed a highly active and robust trifunctional electrocatalyst derived from Prussian blue analogs, where Co₄N nanoparticles are encapsulated by Fe embedded in N‐doped carbon nanocubes to synthesize hierarchically structured Co₄N@Fe/N–C for rechargeable zinc–air batteries and overall water‐splitting electrolyzers. As confirmed by theoretical and experimental results, the high intrinsic oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction activities of Co₄N@Fe/N–C were attributed to the formation of the heterointerface and the modulated local electronic structure. Moreover, Co₄N@Fe/N–C induced improvement in these trifunctional electrocatalytic activities owing to the hierarchical hollow nanocube structure, uniform distribution of Co₄N, and conductive encapsulation by Fe/N–C. Thus, the rechargeable zinc–air battery with Co₄N@Fe/N–C delivers a high specific capacity of 789.9 mAh g⁻¹ and stable voltage profiles over 500 cycles. Furthermore, the overall water electrolyzer with Co₄N@Fe/N–C achieved better durability and rate performance than that with the Pt/C and IrO₂ catalysts, delivering a high Faradaic efficiency of 96.4%. Along with the great potential of the integrated water electrolyzer powered by a zinc–air battery for practical applications, therefore, the mechanistic understanding and active site identification provide valuable insights into the rational design of advanced multifunctional electrocatalysts for energy storage and conversion.