Transition metal chalcogenides will be in situ transformed into metal oxyhydroxides during oxygen evolution reaction (OER) process in alkaline medium. However, most of these compounds only undergo surface reconstruction under operating conditions, which contains a large percentage of inactive atoms in the core, thus limiting the exposure of the active sites. Here, we synthesize a Ni-Mo-Se precatalyst with three-dimensional hierarchical structure and develop a facile on-site electrochemical activation strategy for achieving deep reconstruction of the precatalyst. Using the combination of multiple spectroscopic characterizations and high resolution electron microscopy techniques, we unravel that the Ni-Mo-Se precatalyst is deeply reconstructed into γ-NiOOH with co-leaching of Mo and Se after the anodic oxidation. Such flower-like γ-NiOOH is constituted by distorted ultrathin nanosheets with a thickness of ∼4.5 nm and contains abundant intercalated species such as water and OH^-/CO₃^2-, thus offering a large quantity of accessible active sites. To reach the current density of 10 mA cm^-2, the derived electrode requires an overpotential of only 244 mV, outperforming almost all the reported analogues. This work highlights the reconstruction chemistry and provides a simple method for the preparation of efficient OER electrocatalyst.

在碱性介质中的析氧反应 (OER) 过程中，过渡金属硫属化物将原位转化为金属羟基氧化物。然而，这些化合物中的大多数仅在操作条件下进行表面重建，其核心中含有大量非活性原子，从而限制了活性位点的暴露。在这里，我们合成了具有三维分级结构的 Ni-Mo-Se 预催化剂，并开发了一种简便的现场电化学活化策略，以实现预催化剂的深度重构。结合多种光谱表征和高分辨率电子显微镜技术，我们发现 Ni-Mo-Se 预催化剂在阳极氧化后通过 Mo 和 Se 的共浸而被深度重构为 γ-NiOOH。^- /CO ₃ ^2-，从而提供大量可访问的活性位点。为了达到 10 mA cm ^-2的电流密度，衍生电极只需要 244 mV 的过电位，几乎优于所有报道的类似物。这项工作突出了重建化学，并为制备高效的 OER 电催化剂提供了一种简单的方法。