High Selective Electrochemical Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol on RuO₂–SnO₂–TiO₂/Ti Electrode

Abstract

Electrocatalytic hydrogenation is a promising method to synthesize high value-added chemicals under mild conditions. However, in the case of converting cinnamaldehyde (CAL) into cinnamyl alcohol (COL), this approach is accompanied by the competitive side reactions, including hydrodimerization, C═C saturation, and hydrogen evolution. In this work, a high selectivity to cinnamyl alcohol of 88.86% at 58.00% conversion was successfully achieved on a thermally decomposed RuO2–SnO2–TiO2/Ti cathode with a rutile sosoloid crystal structure, which surpasses the low selectivity (<15%) over various metal electrodes. Density functional theory calculation findings demonstrate that CAL interacts with the active RuO2 sites preferentially via C═O rather than C═C, with the energy barrier of CAL hydrogenation toward COL being significantly reduced. The introduction of SnO2 is efficient to improve the Faradaic efficiency by restraining hydrogen evolution, but would result in dimers as the main products at high content. In addition, low pH value and high electrode overpotential benefit the generation of COL and the inhibition of dimerization products.