Activated M,S co-doping (M = Ni, Co, Mn) inverse spinel oxides with mixed mechanisms for water oxidation

Inverse spinels with characteristic structures are one of the most popular electrocatalytic materials, but typically have limited intrinsic activities for oxygen evolution reactions (OER). Here, taking the conventional inverse spinel Fe3O4 as an example, a series of M (M = Ni, Co, Mn) and S co-doped Fe3O4 OER catalysts are selected by the guidance from theoretical simulations, and then experimentally verified by hydrothermally growing M and S co-doped Fe3O4 on iron foams (M,S-Fe3O4/IF). Based on experimentally and theoretically investigating their OER performance, M,S-Fe3O4/IF are considered to follow mixed OER mechanisms including adsorbate evolution mechanism and lattice oxygen mechanism, and Ni,S-Fe3O4/IF and Co,S-Fe3O4/IF display low overpotentials of 276 and 300 mV at 100 mA cm-2, respectively. Particularly, the Co atoms into S-Fe3O4/IF serve as promoters for in-situ Fe dissolution and redeposition of electrochemical reconstruction during alkaline OER processes. This work contributes new avenues for designing spinel-type materials with mixed OER mechanisms.