Vacancy defect tuning of electronic structures of transition metal (hydr)oxide-based electrocatalysts for enhanced oxygen evolution

Abstract

Electrocatalytic water splitting has already been regarded as a promising approach to generate pure hydrogen (H₂) and oxygen (O₂). However, the oxygen evolution reaction (OER) occurring at the anode during water splitting is very sluggish, because it involves four-electron oxidation steps. Therefore, developing highly efficient and cost-effective electrocatalysts to accelerate its reaction rate and lower its reaction barrier is of great significance, but still remains a big challenge. Strikingly, transition metal (hydr)oxide-based electrocatalysts have attracted wide research interest owing to their high intrinsic activity and low-cost feature. Unfortunately, these transition metal (hydr)oxide-based electrocatalysts always suffer from relatively low conductivity. To address this problem, some efficient strategies have been reported to enhance their conductivity by tuning the electronic structures, further boosting their performances. In this review, three state-of-the-art defect-tuning strategies, including oxygen vacancy defects, metal cation vacancy defects and multivacancy defects, for boosting the OER performances of transition metal (hydr)oxide-based electrocatalysts are summarized. It is found that defects can rationally regulate the electronic structures of transition metal (hydr)oxide-based electrocatalysts, improve the conductivity, optimize the adsorption ability with intermediates and lower the reaction energy barrier of the OER, consequently enhancing their electrocatalytic performances. These defect-tuning strategies open a new avenue for boosting the electrocatalytic performances of low-cost transition metal (hydr)oxide-based nanomaterials, making them promising candidates for replacinge noble metal catalysts for large-scale electrochemical water splitting.