Stoichiometry-Dependent Oxygen Evolution Electrocatalysis on Open-Tubular Nitrogen-Doped Carbon Column Supported Transition Metal Oxides

Ni-, Co-, and Fe-based transition metal oxides have been extensively studied as heterogeneous electrocatalysts for water oxidation in alkaline media. Here, we investigated how metal composition affects the oxygen evolution electrocatalysis and plotted the intrinsic catalytic response to metal stoichiometries in 21 unary, binary, and ternary transition metal oxides. For the first time, we developed a charge transfer complex [metal-7,7,8,8-tetracyanoquinodimethane (M@TCNQ)]-templated strategy to prepare transition metal oxides supported on open-tubular nitrogen-doped carbon columns, containing Ni, Co, and Fe with excellent stoichiometric controllability as well as element distribution uniformity. We observed strong synergistic effects between different metal components; in particular, a small concentration of Fe significantly improves the electrocatalytic activity and the presence of Co dramatically reduces the Tafel slopes. Through contour mapping of the intrinsic kinetic parameters, the best electrocatalytic parameters of the series were attained with a composition of Ni40Co40Fe20Ox, showing a geometric current density of 10 mA cm(-2) at 220 mV overpotential, alongside a Tafel slope of similar to 60 mV dec(-1) and a good stability over 50 h. This work illuminates the importance of synergistic effects between various metal compositions and provides a solid foundation for the broad exploration of other mixed transition metal oxide combinations.