Auto-programmed construction of an iron-incorporated cobalt-molybdenum complex towards enhanced electrocatalytic water oxidation

Development of metal complexes which can be used directly as electrocatalysts for oxygen evolution reaction (OER) is arousing great interest although still in its infancy. Here, an amorphous iron-incorporated cobalt-molybdenum-dithiooxamide (Dto) complex, Fe-CoMo(Dto), which can be applied directly for water oxidation, has been developed using an one-step room-temperature coordination polymerization and self-assembly process. In-situ electrochemical activation of Fe-CoMo(Dto) during electrocatalytic operation promotes structural evolution to form electrocatalytically active species for OER. Detailed investigation of the intermediates obtained after different cyclic voltammetry (CV) cycles of OER measurement showed that amorphous spherical Fe-CoMo(Dto) nanoparticles evolve gradually into corresponding metal (oxyhydr)oxides with hexagonal nanoplate shapes, which have been identified to be real active species for enhanced OER activity. Consequently, the so-activated Fe-CoMo(Dto) complex exhibits remarkable electrocatalytic activity for OER, with a low overpotential of 294 mV at a current density of 10 mA cm−2 and a reduced Tafel slope of 66 mV dec−1.