Understanding and designing versatile electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolyte is of great interest and importance towards overall water splitting. Here we investigated the crystal-plane-dependent electrocatalytic activity of NiCo₂O₄ crystals by combining experimental studies and theoretical calculations for the first time. It is revealed that NiCo₂O₄ nanosheet exposing {1 1 0} crystal planes shows higher catalytic activity for both HER and OER than that of NiCo₂O₄ octahedron exposing {1 1 1} crystal planes and NiCo₂O₄ truncated octahedron exposing {1 1 1} and {1 0 0} crystal planes. Furthermore, we grew the nanosheet with {1 1 0} planes on nickel foam (NF), which could guarantee fast electron and ion transport, rapid release of evolved bubbles and good structural stability, leading to the improved electrochemical performance. Acting as both anode and cathode electrocatalysts with a two-electrode electrolyzer in alkaline medium, NiCo₂O₄ nanosheet array produced a small cell voltage of 1.59 V to drive a current density of 10 mA cm⁻². The research presented here is of both fundamental and instructional significance because it unveils that selectively exposing specific crystal planes is very effective to receive promising catalysts for overall water splitting.

理解和设计用于碱性电解液中氢释放反应（HER）和氧释放反应（OER）的多功能电催化剂，对整体水分解具有重要意义和重要性。在这里，我们首次结合实验研究和理论计算，研究了NiCo ₂ O ₄晶体的晶面依赖性电催化活性。结果表明，暴露{1 1 0}晶面的NiCo ₂ O ₄纳米片对HER和OER的催化活性均高于暴露{1 1 1}晶面和NiCo ₂ O ₄的NiCo ₂ O ₄八面体。截断的八面体，暴露{1 1 1}和{1 0 0}晶面。此外，我们在镍泡沫（NF）上生长了具有{1 1 0}面的纳米片，这可以保证快速的电子和离子传输，快速释放生成的气泡和良好的结构稳定性，从而改善电化学性能。NiCo ₂ O ₄纳米片阵列在碱性介质中同时充当双电极电解槽的阳极和阴极电催化剂，产生了1.59 V的小电池电压，以驱动10 mA cm ^-2的电流密度。此处提出的研究具有基础和指导意义，因为它揭示了选择性地暴露特定的晶面对于接受有希望的整体水分解催化剂非常有效。