The electronic structure of transition metal oxides for oxygen evolution reaction

Electrolysis of water to produce hydrogen and oxygen is a promising pathway for the storage of renewable energy in form of chemical fuels. The efficiency of the overall process is usually limited by the sluggish kinetics of the oxygen evolution reaction (OER) due to a complex four-electron/proton transfer mechanism. Therefore, the most crucial step for water electrolysis to become a widespread industrial process is to develop efficient electrocatalysts capable of driving the OER at a low overpotential. In this article, we present a review of the recent understanding of low-cost transition metal oxide-based catalysts for electrochemical OER. Our main focus is on the fundamental understanding of the electronic structure of these materials and its relationship with the catalytic activity and the reaction mechanism. We detail the electronic structure descriptors of the OER performance that have provided guidelines for the development of advanced electrocatalysts. Strategies to enhance the activity based on such electronic structure guidelines, including doping, strain and defect engineering are also discussed. Finally, we summarize the existing challenges and present perspectives for the future development of the field.