Reduction of Transition-Metal Columbite-Tantalite as a Highly Efficient Electrocatalyst for Water Splitting

We successfully report a liquid-liquid chemical reduction and hydrothermal synthesis of a highly stable columbite-tantalite electrocatalyst with remarkable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in acidic media. The reduced Fe0.79Mn0.21Nb0.16Ta0.84O6 (CTr) electrocatalyst shows a low overpotential of 84.23 mV at 10 mA cm(-2) and 103.7 achieved at 20 mA cm(-2) current density in situ for the HER and OER, respectively. The electrocatalyst also exhibited low Tafel slopes of 104.97 mV/dec for the HER and 57.67 mV/dec for the OER, verifying their rapid catalytic kinetics. The electrolyzer maintained a cell voltage of 1.5 V and potential-time stability close to that of Pt/C and RuO2. Complementary first-principles density functional theory calculations identify the Mn sites as most active sites on the Fe0.75Mn0.25Ta1.875Nb0.125O6 (100) surface, predicting a moderate Gibbs free energy of hydrogen adsorption (Delta G(H*) approximate to 0.08 eV) and a low overpotential of eta = 0.47 V. The vertical bar Delta GMn(H*)vertical bar = 0.08 eV on the Fe0.75Mn0.25Ta1.875Nb0.125O6 (100 surface is similar to that of the well-known and highly efficient Pt catalyst (vertical bar Delta GPt(H*)vertical bar approximate to 0.09 eV).