Replacing Anodic Oxygen Evolution Reaction with Organic ­Oxidation: The Importance of Metal (Oxy)Hydroxide Formation as the Active Oxidation Catalyst

AbstractHybrid water electrolysis has been explored for the electrochemical oxidation of biomass, glucose, alcohols, amines, urea, etc. to produce value-added products. The integration of cathodic hydrogen evolution reaction (HER) with anodic organic reaction (AOR) improves the energy efficiency of the electrolyzer by reducing the cell voltage of the overall process. Tremendous progress has been achieved in AOR by using transition-metal-based catalysts. These transition-metal-based catalysts undergo anodic activation in the alkali medium to form metal (oxy)hydroxide [M(O)x(OH)y] as the active catalyst. The atomic and electronic structure of M(O)x(OH)y essentially controls the conversion efficiency and product selectivity for AOR. In this Account, we have described the design of the AOR precatalyst, its anodic activation, and the basic principles of the integration of cathodic HER with AOR. The structural features of the precatalyst and the active catalyst have been described with representative examples. The recent progress and advancement in this field have been explained, and the future scope and challenges associated with AOR have been addressed.1 Introduction2 Anodic Organic Oxidation Reactions3 Activity and Selectivity of Anodic Organic Reaction4 Anodic Activation of Transition-Metal-Based Catalysts5 Mechanism of Anodic Organic Oxidation6 Perspective and Outlook