Developing highly active and low-cost heterogeneous catalysts toward overall electrochemical water splitting is extremely desirable but still a challenge. Herein, we report pyrite NiS₂ nanosheets doped with vanadium heteroatoms as bifunctional electrode materials for both hydrogen- and oxygen-evolution reaction (HER and OER). Notably, the electronic structure reconfiguration of pyrite NiS₂ is observed from typical semiconductive characteristics to metallic characteristics by engineering vanadium (V) displacement defect, which is confirmed by both experimental temperature-dependent resistivity and theoretical density functional theory calculations. Furthermore, elaborate X-ray absorption spectroscopy measurements reveal that electronic structure reconfiguration of NiS₂ is rooted in electron transfer from doped V to Ni sites, consequently enabling Ni sites to gain more electrons. The metallic V-doped NiS₂ nanosheets exhibit extraordinary electrocatalytic performance with overpotentials of about 290 mV for OER and about 110 mV for HER at 10 mA cm^–2 with long-term stability in 1 M KOH solutions, representing one of the best non-noble-metal bifunctional electrocatalysts to date. This work provides insights into electronic structure engineering from well-designed atomic defect metal sulfide.

中文翻译：

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通过工程杂原子缺陷向黄铁矿NiS ₂ 进行电子结构重构，促进了总水分解

向整体电化学水分解开发高活性和低成本的非均相催化剂是非常需要的，但仍然是一个挑战。在这里，我们报告掺杂有钒杂原子的黄铁矿NiS ₂纳米片作为氢和氧逸出反应（HER和OER）的双功能电极材料。值得注意的是，通过工程钒（V）位移缺陷，从典型的半导体特性到金属特性，可以观察到黄铁矿NiS ₂的电子结构重构，这已通过实验性温度依赖性电阻率和理论密度泛函理论计算得到了证实。此外，详尽的X射线吸收光谱测量显示NiS _2的电子结构重配置X射线源于电子从掺杂的V到Ni的转移，因此使Ni能够获得更多的电子。金属V掺杂的NiS ₂纳米片表现出非凡的电催化性能，在10 mA cm ^–2下，OER的过电势约为290 mV，HER的过电势约为110 mV，在1 M KOH溶液中具有长期稳定性，代表了最好的非催化性能之一。迄今为止，贵金属双功能电催化剂。这项工作为精心设计的原子缺陷金属硫化物提供了有关电子结构工程的见识。