EARTH-ABUNDANT 3d-TRANSITION METAL METASILICATES AS EFFECTIVE ELECTROCATALYSTS FOR ALKALINE HER: CuZnSiO3 OUTPERFORMS CuSiO3 AND ZnSiO3.

Abstract

Hydrogen evolution reaction (HER) is a key reaction in electrochemical water splitting for hydrogen production leading to the development of potentially sustainable energy technology. Importantly, the catalysts required for HER must be earth-abundant for their large-scale deployment; silicates representing one such class. Herein, we have synthesized a series of transition mono- and bi- metal metasilicates (with SO32- group) using facile wet-chemical method followed by calcination at a higher temperature. The structural and morphological studies their unique crystal structure and distinctive morphology, as well as the surface texture, with the band gap ranges 1.49-2.24 eV. Interestingly, CuZnSiO3, with all earth-abundant elements, exhibits a band gap of 1.67 eV, shows impressive electrocatalytic properties. We show that CuZnSiO3 exhibits HER activity with much lower overpotential (h = 151 mV) at 10 mA cm-2 under alkaline conditions. The CuZnSiO3 electrode also shows good electrocatalytic stability (ΔE = 24 mV) even after 25 hours of chronoamperometric stability test and the performance is comparable to the commercial Pt/C catalyst under similar conditions. Finally, detailed electronic structure studies employing density functional theory (DFT) as well as electronic transport studies were performed to understand and elucidate the superior performance of CuZnSiO3 over the CuSiO3 and ZnSiO3 electrocatalysts.