Exploring Hydroxyl Group-Mediated Phase Transformations in Transition Metal Catalysis: A Combined Theoretical and Experimental Investigation

Abstract

An in-depth exploration of hydroxyl group-mediated phase transformations, which regulate catalytic activity, is crucial for the development of high-performance catalysts. This study systematically examined the impact of four phase structures (TM3O4, TM2O3, TM(OH)2, and TMOOH) on the local atomic environments, electronic structures, and catalytic activity of five-coordinated transition metal (TM = Fe, Co, and Ni) active sites using density functional theory. A progressive increase in coordinated hydroxyl groups from TM2O3/TM3O4 to TMOOH and subsequently to TM(OH)2 phase induced significant variations, with TM cations in the TM(OH)2 phase showing elongated TM-O bonds, reduced d-electron densities, and enhanced catalytic performance. Experimental validation using FeCoNi-based catalysts confirmed that the prepared S-Fe5Ni4Co1 specimen with TM(OH)2 phase exhibited superior oxygen evolution reaction performance, achieving overpotentials of 246/296 mV at current densities of 10/100 mA cm-2, a Tafel slope of 42.8 mV dec-1, high turnover frequency (0.033 s-1), and excellent stability. This study highlights the critical role of phase structure in catalytic activity and offers a strategy for designing efficient TM-based catalysts via precise phase composition control.

Keywords: Phase Transition, Coordinated hydroxyl groups, Theory-experiment synergy, Oxygen evolution reaction