The ion effect on electrocatalytic oxidation reactions

The electrode/electrolyte interface has a profound impact on the chemical environment of electrocatalysis. Specifically, changing the type or concentration of ions in electrolyte composition may modulate the activity and selectivity of the target product, which is often called the ion effect. The cation effect has been widely recognized for greatly impacting cathodic reactions, such as the hydrogen evolution reaction and carbon dioxide reduction reaction. Comparatively, the ion effect for anodic reactions has been less studied. However, owing to the significant contribution of anodic reactions to the overall efficiency of electrolytic systems and emerging interest in synthetic electrochemistry, researchers have revived interest in exploring the ion effect on anodic reactions. In this review, we summarize the recent progress on the anodic ion effect. The reactions span from the widely studied oxygen evolution reaction under different pH conditions to alcohol oxidation and even electro-synthetic reactions. The ion effect on activity and selectivity are outlined, from which general principles and influencing mechanisms are clarified. Through the summary of the anodic ion effect, we eventually propose the challenges and prospects for the general ion effect and their wide applications in electrocatalysis.