Selective Electrochemical Hydrogenation of Phenol with Earth-abundant Ni-MoO 2 Heterostructured Catalysts: Effect of Oxygen Vacancy on Product Selectivity.

Herein, we report highly efficient carbon supported Ni-MoO 2 heterostructured catalysts for the electrochemical hydrogenation (ECH) of phenol in 0.10 M aqueous sulfuric acid (pH 0.7) at 60 °C. Highest yields for cyclohexanol and cyclohexanone of 95 % and 86 % with faradaic efficiencies of ∼50 % are obtained with catalysts bearing high and low densities of oxygen vacancy (O v ) sites, respectively. In situ diffuse reflectance infrared spectroscopy and density functional theory calculations reveal that the enhanced phenol adsorption strength is responsible for the superior catalytic efficiency. Furthermore, 1-cyclohexene-1-ol is an important intermediate. Its hydrogenation route and hence the final product are affected by the O v density. This work opens a promising avenue to the rational design of advanced electrocatalysts for the upgrading of phenolic compounds.