Constructing atomically dispersed active sites with densely exposed and dispersed double metal-S_x catalytic sites for favorable OER catalytic activity remains rare and challenging. Herein, we design and construct a Fe₁S_x@Co₃S₄ electrocatalyst with Fe single atoms epitaxially confined in Co₃S₄ nanosheets for catalyzing the sluggish alkaline oxygen evolution reaction(OER). Consequently, in ultralow concentration alkaline solutions(0.1 mol/L KOH), such a catalyst is highly active and robust for OER with low overpotentials of 300 and 333 mV at current densities of 10 and 30 mA/cm², respectively, accompanying long-term stability without significant degradation even for 350 h. In addition, Fe₁S_x@Co₃S₄ shows a turnover frequency(TOF) value of 0.18 s⁻¹, nearly three times that of Co₃S₄(0.07 s⁻¹), suggesting the higher atomic utilization of Fe single atoms. Mössbauer and in-situ Raman spectra confirm that the OER activity of Fe₁S_x@Co₃S₄ origins from a thin catalytic layer of Co(Fe)OOH that interacts with trace-level Fe species in the electrolyte, creating dynamically stable active sites. Combined with experimental characterizations, it suggests that the most active S-coordinated dual-metal site configurations are 2S-bridged (Fe-Co)S₄, in which Co-S and Fe-S moieties are shared with two S atoms, which can strongly regulate the adsorption energy of reaction intermediates, accelerating the OER reaction kinetics.

构建具有密集暴露和分散的双金属-S _x催化位点的原子分散活性位点以获得有利的 OER 催化活性仍然很少见且具有挑战性。在此，我们设计并构建了一种 Fe ₁ S _x @Co ₃ S ₄电催化剂，其中 Fe 单原子外延限制在 Co ₃ S ₄纳米片中，用于催化缓慢的碱性析氧反应 (OER)。因此，在超低浓度碱性溶液（0.1 mol/L KOH）中，这种催化剂对 OER 具有高活性和鲁棒性，在 10 和 30 mA/cm ^{2的电流密度下具有 300 和 333 mV 的低过电势}，分别伴随着长期稳定性，即使在 350 小时内也没有显着退化。此外，Fe ₁ S _x @Co ₃ S ₄的转换频率（TOF）值为 0.18 s ^{- 1 ，几乎是 Co} ₃ S ₄（0.07 s ^{- 1} ）的三倍，表明 Fe 单原子利用率更高原子。穆斯堡尔和原位拉曼光谱证实了 Fe ₁ S _x @Co ₃ S _{4的 OER 活性}起源于薄薄的 Co(Fe)OOH 催化层，该催化层与电解质中的痕量 Fe 物种相互作用，产生动态稳定的活性位点。结合实验表征，表明最活跃的 S 配位双金属位点配置是 2S 桥接 (Fe-Co)S ₄，其中 Co-S 和 Fe-S 部分与两个 S 原子共享，可以强烈调节反应中间体的吸附能，加速OER反应动力学。