Efficient oxygen evolution reaction (OER) electrocatalyst is essential for water electrolysis. Herein, high-performance NiFe-based layered double hydroxides (LDH), phosphide and sulfide OER pre-catalysts were fabricated and their distinct activity was unveiled. The as-prepared Ni_xFe_1−xS exhibits ultralow OER overpotential of 122 mV at 10 mA cm⁻² in 1 M KOH. The alkali-electrolyzer using Ni_xFe_1−xS electrodes achieve superior performance exhibiting a voltage of 1.46 V at 10 mA cm⁻². Experimental analysis reveals that, during OER, Fe dissolution into electrolyte occurs for NiFe LDH and Ni_xFe_1−xP, which were both converted into NiOOH, well explaining their similar activity. Interestingly, Fe dissolution is significantly mitigated in Ni_xFe_1−xS, forming partially oxidized Fe₂O₃/FeOOH species. Theoretical calculations confirmed that Fe₂O₃/FeOOH is responsible for the enhanced OER energetics of Ni_xFe_1−xS. These observations provide new insights on the distinct activity of NiFe-based electrocatalysts, guiding their rational design as well.

高效的析氧反应 (OER) 电催化剂对于水电解至关重要。在此，制备了高性能 NiFe 基层状双氢氧化物 (LDH)、磷化物和硫化物 OER 预催化剂，并展示了它们独特的活性。所制备的 Ni _x Fe _1-x S在 1 M KOH 中在 10 mA cm ^{-2 下}表现出 122 mV 的超低 OER 过电位。使用 Ni _x Fe _1-x S 电极的碱电解槽实现了优异的性能，在 10 mA cm ^{-2 下}表现出 1.46 V 的电压。实验分析表明，在 OER 过程中，NiFe LDH 和 Ni _x Fe _1-x发生 Fe 溶解到电解质中P，两者都转化为 NiOOH，很好地解释了它们的相似活性。有趣的是，Fe 溶解在 Ni _x Fe _1-x S 中显着减轻，形成部分氧化的 Fe ₂ O ₃ /FeOOH 物种。理论计算证实，Fe ₂ O ₃ /FeOOH 是导致 Ni _x Fe _1-x S 的OER 能量增强的原因。这些观察结果为 NiFe 基电催化剂的独特活性提供了新的见解，也指导了它们的合理设计。