Abstract Efficient electrocatalysts based on earth-abundant elements are urgently required for promoting the efficiency of electrochemical water splitting. In this work, heterostructures of CoNi2S4/Ni3S2 on nickel foam (CoNi2S4/Ni3S2@NF) are synthesized by a facile one-step hydrothermal method as promising bifunctional electrocatalysts. To achieve an electrocatalytic current density of 10 mA cm−2 in 1 M KOH solution, the CoNi2S4/Ni3S2@NF electrode requires overpotential as low as 171 mV and 243 mV for HER and OER, respectively. Furthermore, the overall water splitting device with CoNi2S4/Ni3S2@NF electrode as both cathode and anode requires 1.65 V to offer current density of 10 mA cm−2. Density functional theory calculations reveal that the strong coupling interactions between CoNi2S4 and Ni3S2 synergistically optimized the electronic structure, thus enhancing the electrochemical water splitting performances. Surfaces oxidation of CoNi2S4/Ni3S2@NF electrode is considered to hinder the electrochemical activities for OER. The present work not only provides a promising bifunctional electrocatalyst for water splitting but also expands the applications of CoNi2S4 based materials.

中文翻译：

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泡沫镍上的花状 CoNi2S4/Ni3S2 纳米片簇作为双功能电催化剂用于整体水分解

摘要 为了提高电化学分解水的效率，迫切需要基于地球丰富元素的高效电催化剂。在这项工作中，通过简便的一步水热法合成了泡沫镍上的 CoNi2S4/Ni3S2 异质结构（CoNi2S4/Ni3S2@NF），作为有前景的双功能电催化剂。为了在 1 M KOH 溶液中实现 10 mA cm-2 的电催化电流密度，CoNi2S4/Ni3S2@NF 电极对 HER 和 OER 的过电位分别需要低至 171 mV 和 243 mV。此外，以 CoNi2S4/Ni3S2@NF 电极作为阴极和阳极的整个水分解装置需要 1.65 V 以提供 10 mA cm-2 的电流密度。密度泛函理论计算表明 CoNi2S4 和 Ni3S2 之间的强耦合相互作用协同优化了电子结构，从而提高电化学水分解性能。CoNi2S4/Ni3S2@NF 电极的表面氧化被认为会阻碍 OER 的电化学活性。目前的工作不仅为水分解提供了一种有前途的双功能电催化剂，而且还扩展了 CoNi2S4 基材料的应用。