Selective oxidation of alcohols to their corresponding aldehyde or carboxylic acid is one of the most important classes of organic synthesis reactions. In addition, electrochemical alcohol oxidation is considered a viable anode reaction that can be paired with H<sub>2</sub> evolution or other reductive fuel production reactions in electrochemical and photoelectrochemical cells. NiOOH, a material that has been extensively studied as an oxygen evolution catalyst, is among the most promising electrocatalysts for selective alcohol oxidation. Electrochemical alcohol oxidation by NiOOH has been understood since the 1970’s to proceed through a hydrogen atom transfer to NiOOH. In this study, we establish that there is a second, more dominant general alcohol oxidation pathway on NiOOH enabled at more positive potentials. Using a newly developed electrochemical procedure, we deconvoluted the currents corresponding to these two pathways for various alcohols and aldehydes. The results show that alcohols and aldehydes have a distinct difference in their respective preferences for the two oxidation pathways. We also examined the effect of pH and the concentration of aliphatic and aromatic alcohols and aldehydes to determine the key factors and steps that affect the kinetics of the two oxidation pathways. Through these experiments we provide a comprehensive mechanistic understanding of the two pathways.

Unraveling two pathways for electrochemical alcohol and aldehyde oxidation on NiOOH

ACS Spring 2022

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