On the efficiency of phenol and cyclohexanone electrocatalytic hydrogenation — Effect of conditioning and working pH in acetic acid solution on palladium/fluorine-doped tin dioxide supported catalyst

The electrocatalytic hydrogenation (ECH) of phenol and cyclohexanone was performed on a conductive Pd/SnO2:F catalyst. The catalyst was obtained by the impregnation method. We studied the influence of the pH of the supporting electrolyte, the conditioning pH, and the quantity of the conditioning charge passed before hydrogenation. Fourier transform infrared spectroscopy analysis showed that the functionalization of the catalyst surface by the acetic acid electrolyte depends on the pH. A direct correlation was observed between the efficiency of the hydrogenation, the pH of the electrolyte, and the electrode conditioning charge. Phenol hydrogenation was favored in acidic media, whereas cyclohexanone hydrogenation needed an acidic medium for conditioning and a basic medium for hydrogenation. The ECH rate appeared to depend on the functionalization of the catalyst surface, the adsorption of the target organic molecule on the catalyst, and its structural modification with the pH.