Role of High-Valence Metal Dissolution in Oxygen Evolution Kinetics of the Advanced FeNiO<i>_x</i> Catalysts

The incorporation of high-valence metals into FeNi-based oxides has been widely accepted as an efficient approach for facilitating the alkaline oxygen evolution reaction (OER), but the corresponding structure–property relationship remains unclear due to the lack of identification of the real structure. In this study, we reveal the surface evolution processes of M-doped FeNi oxides (M is Mo, V, and W) and elucidate the role of M dissolution in enhancing oxygen evolution kinetics. Taking Mo as an example, the high-valence metal Mo was doped into FeNiOx and its leaching behavior was observed during OER. By combining in situ Raman analysis, electrochemical measurement, and first-principles calculation, it was unveiled that the electro-dissolution of Mo, in the form of MoO42–, led to preferential removal of lattice oxygen, thereby facilitating the adsorption step of OH and triggering the lattice oxygen-mediated mechanism for promoting OER. Consequently, the optimized FeNiMoOx displayed an overpotential of only 235 mV to reach 10 mA/cm2 and a 30-fold enhancement in specific activity compared with that of FeNiOx at 1.53 V. Our findings provide a different perspective on the intricate association between dissolution of high-valence metal and alkaline OER performance, elucidating the key role of the dissolution-induced structure change on promoting the OER mechanism.