Elongated M–O Bonds Facilitate Dynamic Active Phase Reconfiguration for Enhanced Water Electrolysis Efficiency

Controlling active phase reconstruction is critical for enhancing the oxygen evolution reaction (OER) performance in water electrolysis. In this study, a series of catalysts D-Ni/NiMO (M = Fe, Co, Mn) with varying M–O bond lengths were synthesized using nickel oxide as a model electrocatalyst. Among them, Ni/NiCoO, featuring the longest M–O bond length, received particular attention. Comprehensive in situ and ex situ characterizations, including synchrotron radiation X-ray absorption spectroscopy, revealed that elongation of M–O bonds promotes the dynamic formation of active OER phases. A quantitative relationship was established: longer M–O bond lengths correlate with improved catalytic performance. Mechanistic studies revealed that stretched M–O bonds facilitate electron depletion from the z² orbital, enhancing metal–oxygen electron delocalization, and promoting the generation of highly active species (e.g., high-valent Ni³⁺) during the reconstruction process. As a result, the D-Ni/NiCoO catalyst exhibits superior OER performance, requiring an ultralow overpotential of only 300 mV at a current density of 100 mA cm^–2, while maintaining long-term stability over 60 h. Under industrially relevant operating conditions, the fully assembled D-Ni/NiCoO||Pt/C device showcased a superior performance profile, requiring a cell voltage of just 2.1 V to achieve 1000 mA cm^–2 and demonstrating robust operational durability for 50 h. This study provides fundamental insights into the relationship between M–O bond lengths and active phase reconstruction, offering a rational strategy for designing high-performance OER catalysts suitable for operation under industrial-level current densities.