Design of Novel transition metal based multiphase stannate: An efficient electrocatalyst for oxygen evolution reaction

Abstract

The crystal phase dependency of stannate based sample was well-understood here. The electrocatalytic activity and stability of ZnSnO3 and Zn2SnO4 have been investigated for the production of O2 gas from water. The well-defined perovskite phase of ZnSnO3 and Ruddlesden-Popper phase of Zn2SnO4 nanoparticles was synthesized via the hydrothermal route. Changing the tin precursor results in the phase transformation of the perovskite phase of ZnSnO3 into the Ruddlesden-Popper phase of Zn2SnO4 which was characterized by XRD analysis, as well as by high-resolution transmission electron microscopy. It was found that the transformation of phase from perovskite to the Ruddlesden-Popper phase affects the overpotential value for zinc stannate which changes electrochemical catalytic activity resulting from the active site distribution, oxygen vacancy concentration, and electrical conductivity changes a lot. The perovskite phase of ZnSnO3 exhibits better catalytic activity for oxygen evolution reaction (OER) with an onset potential of 430 mV than the Ruddlesden-Popper phase in an alkaline medium. Furthermore, their performance can be enhanced by changing two factor such as i) replacing A site with different transition metal (Mn, Fe, Co) cations and ii) annealing under a hydrogen atmosphere. We established a relationship for the activity of the catalyst for oxygen evolution reaction by changing zinc with other transition metal cations. This relationship exhibits trends in reactivity (Zn < Mn < Fe < Co), which is governed by the strength of the metal oxygen bond, electronegativity of metal, and the number of ‘d’ electrons in antibonding orbitals.