Cosynergistic Molybdate Oxo‐Anionic Modification of FeNi‐Based Electrocatalysts for Efficient Oxygen Evolution Reaction

Abstract Catalytic synergy is an unresolved activity descriptor in energy conversion reactions. Here, this study reports the synergistically enhanced intrinsic oxygen evolution reaction activity of a FeNi model catalyst modified with molybdate oxo‐anions via concertedly boosted surface/interface interactions such as interfacial charge transfer, surface intermediate adsorption, in situ phase transformation, and gas bubble evolution. Capturing such cosynergistic impact reveals the accelerated transition of oxygen deprotonation to oxyhydroxide state, ready‐to‐function Fe and Ni active sites, the instant transformation of Fe and Ni local microenvironments to γ ‐FeOOH and β ‐NiOOH phases, and ultrafast gas bubble growth and release. The accelerated oxygen bubble evolution dynamic is monitored in operando with a decreased dynamic variation of the interfacial Faradaic resistance. Such cosynergistic molybdate modification results in a tenfold increase in oxygen evolution turnover frequency as well as a 55 mV decrease in the overpotentials to deliver 10 and 1000 mA cm −2 with respect to the FeNi‐model catalyst.