Understanding the catalysis mechanism of the sluggish oxygen evolution reaction (OER) involved in water splitting is of vital importance for the development of clean hydrogen energy. Earth-abundant transition-metal (oxy)hydroxide with low cost and high performance is one of the most promising OER catalysts. These catalysts often dynamically and heterogeneously transform from inactive pre-catalysts into active phases under operation conditions, and thus, the operando/in situ method is needed for the direct observation. Herein, using in situ Raman spectroscopy and density functional theory simulation, we correlate the OER activity with the dynamic crystal- and electronic-structure reconstruction of nano-sheet cobalt hydroxide. A complicated dual-transformation path is observed as the applied voltage is gradually increased; the pristine single-phase α-Co(OH)₂ catalyst transforms into the hydrous Co(OH)₂ phase through hydroxide intercalation, then to mixed β/γ-CoOOH phases through dehydration and dehydrogenation, and finally to OER-active γ-CoOOH_x and β-CoOOH_y. Moreover, the observed spectral and Tafel behaviors at different scan rates manifest the rate-dependent formation of the dual-active-phase, demonstrating the correlation between the OER ability and thermodynamics of structural reconstruction, which is critical in the fabrication of high-activity catalysts.

中文翻译：

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从原位拉曼光谱观察到的双通路动态形成双活性位点的电催化剂

了解水分解中缓慢的析氧反应（OER）的催化机理对于清洁氢能的发展至关重要。地球上丰富的过渡金属（氧）氢氧化物具有低成本和高性能，是最有前途的OER催化剂之一。这些催化剂通常在操作条件下从非活性预催化剂动态且非均相地转变为活性相，因此需要操作/原位方法进行直接观察。在此，原位使用拉曼光谱和密度泛函理论模拟，我们将 OER 活性与纳米片状氢氧化钴的动态晶体和电子结构重建联系起来。随着施加的电压逐渐增加，观察到一个复杂的双变换路径；原始单相α-Co(OH) ₂催化剂通过氢氧化物插层转化为含水Co(OH) ₂相，然后通过脱水和脱氢转化为混合β/γ-CoOOH相，最后转化为具有OER活性的γ-CoOOH _x和 β-CoOOH _y. 此外，在不同扫描速率下观察到的光谱和 Tafel 行为表明了双活性相的速率依赖性形成，证明了 OER 能力与结构重建的热力学之间的相关性，这对于制造高活性催化剂至关重要.