Recent advancements in defect engineering have significantly improved catalysis by modulating the electronic structure and enhancing the intrinsic abilities of catalysts. However, establishing a clear structure-property relationship at the atomic level remains a challenge due to the inherent polydispersity of catalysts, which hinders a comprehensive understanding of the defect catalysts. Atomically precise metal nanoclusters can serve as model catalysts because of their perfect monodispersity and well-defined structure. While, the understanding about defects in atomically precise metal nanoclusters is insufficient. This review encompasses various types of defects (such as heteroatom incorporation, vacancies, ligand deficiencies, etc.) in atomically precise coingage metal clusters, characterization methods, and their applications within the realm of catalysis. At the conclusion of this review, we propose several prospects, including the controllable construction of defects, further enhancement of the performance of clusters with defects, and monitoring the in-situ evolution of defects in clusters during catalysis. The purpose of this review is to deepen the understanding of defects in atomically precise clusters, establish the relationship between defect structure and catalytic performance, and offer valuable insights for the designing and developing of efficient defect-rich cluster catalysts.

Electrocatalytic reduction reactions play a crucial role in electrochemical energy conversion and storage technology, which are emerging technologies to ameliorate environmental problems. Spinel oxides are widely explored in electrocatalytic oxidation reactions but have a poor intrinsic ability to reduction reactions, making their electrocatalytic ability less effective. To improve this, defect engineering is a valuable method for regulating the electronic structure and coordination environment. Herein, this manuscript discusses the use of defect spinel oxides in electrocatalytic reduction reactions, including the different types of defects, construction methods, and characterization techniques. It also outlines the various applications of defect spinel oxides in different electrocatalytic reduction reactions. Finally, it goes over the challenges and future outlooks for defect spinels. This review aims to thoroughly explain how defect spinels work in electrocatalytic reduction reactions and serve as a helpful guide for creating effective electrocatalysts.