Facet-Dependent Surface Restructuring on Nickel (Oxy)hydroxides: A Self-Activation Process for Enhanced Oxygen Evolution Reaction
Yunduo Yao, Guangming Zhao, Xuyun Guo, Pei Xiong, Zhihang Xu, Longhai Zhang, Changsheng Chen, Chao Xu, Tai‐Sing Wu, Y. L. Soo, Zhiming Cui, Molly Meng‐Jung Li, Ye Zhu
Abstract
Unraveling the catalyst surface structure and behavior during reactions is essential for both mechanistic understanding and performance optimization. Here we report a phenomenon of facet-dependent surface restructuring intrinsic to β-Ni(OH) 2 catalysts during oxygen evolution reaction (OER), discovered by the correlative ex situ and operando characterization. The ex situ study after OER reveals β-Ni(OH) 2 restructuring at the edge facets to form nanoporous Ni 1– x O, which is Ni deficient containing Ni 3+ species. Operando liquid transmission electron microscopy (TEM) and Raman spectroscopy further identify the active role of the intermediate β-NiOOH phase in both the OER catalysis and Ni 1 –x O formation, pinpointing the complete surface restructuring pathway. Such surface restructuring is shown to effectively increase the exposed active sites, accelerate Ni oxidation kinetics, and optimize *OH intermediate bonding energy toward fast OER kinetics, which leads to an extraordinary activity enhancement of ∼16-fold. Facilitated by such a self-activation process, the specially prepared β-Ni(OH) 2 with larger edge facets exhibits a 470-fold current enhancement than that of the benchmark IrO 2, demonstrating a promising way to optimize metal-(oxy)hydroxide-based catalysts.