Extraction of non-noble metal columbite-tantalite as a highly efficient electrocatalyst for water splitting

Abstract

The development of robust and inexpensive electrocatalysts that are capable of catalyzing the overall water splitting reaction is highly essential for large scale production of hydrogen. Herein, we report the successful liquid-liquid extraction and hydrothermal synthesis of a highly stable columbite-tantalite electrocatalysts (Fe0.79Mn0.21Nb0.16Ta0.84O6) with remarkable HER and OER performance in alkaline media. The extracted Fe0.79Mn0.21Nb0.16Ta0.84O6 electrocatalyst shows a low overpotential of 190.2 and 284.8 mV at 10/mA cm-2 in current density in situ for HER and OER, respectively. The electrocatalyst also exhibited low Tafel slopes of 56.36 mV/dec for HER and 112.85 mV/dec for OER, verifying their rapid catalytic kinetics. The electrolyzer maintained the cell voltage of 1.63 V and potential-time stability close to that of Pt/C & RuO2/C. The intrinsic mechanism for the exceptional HER and OER performance was further unravelled through first-principles density functional theory (DFT) calculations, predicting very low Gibbs free energy of hydrogen adsorption (ΔGH* ≈ 0.09 eV) and low overpotential (η = 0.47 eV at the Mn sites) for OER on the Fe0.75Mn0.25Ta1.875Nb0.125O6 catalyst. Our results demonstrate that columbite-tantalite electrocatalysts offer great promise for efficient overall water splitting. Graphical abstract