Defective Metal Oxides: Lessons From CO 2 RR and Applications in NO x RR.

Sluggish reaction kinetics and undesired side reactions (hydrogen evolution reaction and self-reduction) are the main bottlenecks of electrochemical conversion reactions, such as carbon dioxide and nitrate reduction reactions (CO 2 RR and NO 3 RR). To date, conventional strategies to overcome these challenges involve electronic structure modification and modulation of the charge-transfer behavior. Nonetheless, key aspects of surface modification, focused on boosting the intrinsic activity of active sites on the catalyst surface, is yet to be fully understood. Oxygen vacancy (OVs) engineering can tune surface/bulk electronic structure and improve surface active sites of electrocatalysts. The continuous breakthroughs and significant progress in the last decade position OVs engineering as a potential technique for advancing electrocatalysis. Motivated by this, we present the state-of-the-art findings of roles of OVs in both CO 2 RR and NO 3 RR. We start with a description of approaches to constructing OVs and techniques for characterizing OVs. This is followed by an overview of the mechanistic understanding of CO 2 RR and a detailed discussion on roles of OVs in CO 2 RR. Then, we offer insights into the mechanism of NO 3 RR and highlights the potential of OVs on NO 3 RR based on early findings. Finally, the challenges in designing CO 2 RR/NO 3 RR electrocatalysts and perspectives in studying OVs engineering are provided. This article is protected by copyright. All rights reserved.