(197a) Unraveling the Impact of Ni and Mn Impurities on Coooh for Benzyl Alcohol Electrooxidation: Spectroscopic and Kinetic Insights

Electrocatalytic oxidation of small organic molecules from renewable biomass sources provides sustainable means to generate green hydrogen and value-added products. Transition metal oxyhydroxides are key electrocatalysts for organic oxidation reactions (OOR) due to their optimized M²⁺ᵟ–OH bond strength and tunable oxidation states. However, most studies have overlooked the impact of common water impurities, such as iron, nickel, or manganese, which can adsorb onto MOOHs and modulate their performance, even at trace concentrations.

Using cobalt oxyhydroxide (CoOOH) as a model catalyst and benzyl alcohol oxidation (BAOR) as a model reaction, we study the dynamics of Co active sites under catalytically active conditions in the presence of Ni and Mn impurities. Through electrochemical and spectroscopic characterization, along with kinetic modeling, we investigate the impact of Ni and Mn contaminants on the electrocatalytic activity of CoOOH in long-term, non-steady-state reactions, and explore the underlying mechanisms. STEM-EDS characterizations showed the uniform distribution of Ni and Mn impurities and Co on a nickel foam substrate. Spectroscopic characterizations (pXRD and XPS) showed that incorporating these impurities into CoOOH modulated the structural and electronic properties. Electrochemically, Ni improved CoOOH activity in BAOR by reducing potential by 100 mV due to cooperative Co-Ni sites, while Mn enhanced long-term stability. In-situ Raman spectroscopy measurements revealed that CoOOH does not readily transform into CoO₂ during BAOR, indicating a distinct reaction mechanism that avoids CoO₂ formation. Kinetic modelling revealed that BAOR over CoOOH follows a first-order series reaction with benzoic acid as a major product, and the rate-determining step is the H abstraction from the CH or OH bond of benzyl alcohol.

This work contributes to understanding the dynamics of the active sites in electrocatalysts during partial reaction of organic molecules, which can facilitate the targeted design and optimization of highly efficient catalysts towards sustainable electrocatalytic reactions.