Enhanced electrocatalytic performance of bismuth-doped zinc stannate towards OER and HER through oxygen vacancies: p-block metal ion doping empowering d-block

Abstract

In order to meet the future energy requirements of society, electrocatalytic water splitting is considered as one of the efficient methods to produce pure hydrogen fuel on a large scale. Doping has been established as a very effective strategy to engineer the active sites of electrocatalysts to improve their efficacy towards various electrochemical reactions. Herein, we have synthesized Zn₂SnO₄ doped with different metal ions such as Mn²⁺, Bi³⁺, Co³⁺ and Fe³⁺ and studied the electrocatalytic activities of these samples. Among the dopants investigated, Bi³⁺ exhibited the best catalytic activity towards hydrogen evolution reaction (HER) with good stability, high endurance and durability, with a faradaic efficiency (FE) of 88%. The Zn₂SnO₄:Bi³⁺ composition also showed significant catalytic activity towards oxygen evolution reaction (OER) with a FE of 78%. Considering the bifunctional activity of the catalyst, a full cell was configured to carry out overall water splitting. The high catalytic activity of the bismuth-doped samples can be explained on the basis of enhanced electrochemically active surface area aided by the presence of high density of oxygen vacancies.