Defect-induced electronic modification and surface reconstruction of catalysts during water oxidation process

Over the past decade, defect-promoted electrochemical activity and stability have become essential concepts to a rational catalyst design. The interest in defect engineering has been increasing drastically in recent years. Defect-induced electronic modifications and surface reconstruction during water oxidation have been at the focal point of attention because they have been suggested to promote the formation of real active species and/or sites responsible for driving the anodic oxygen evolution reaction (OER). Owing to the rapid development of characterization techniques, the in-depth analysis of the dynamic reconstruction of OER catalysts under operating conditions has become possible. The intrinsic changes in catalyst surface structure, composition, and electronic configuration, which ultimately affect the reaction mechanism, are presently probed using modern in-situ and operando microscopy and spectroscopy techniques. Herein, we present a detailed overview of the different ex-situ, in-situ, and operando characterization techniques generally used to provide crucial insights into the structural, morphological, compositional, chemical, and physical properties of catalysts throughout the water oxidation process. We then elaborate on the indispensable effects of defects on the OER catalytic activity and stability by presenting up-to-date survey literature focused on the characterization of defect-rich catalysts. Finally, we draw attention to the urgent challenges of modern characterization techniques and future research directions to produce defect-enriched, stable OER catalysts that would fast-forward the advance to the future hydrogen economy.