Electrocatalysis as an efficient alternative to thermal catalysis over PtRu bimetallic catalysts for hydrogenation of benzoic acid derivatives

Abstract

The electrocatalytic hydrogenation of aromatic rings in benzoic acid derivatives has arisen as a notionally engaging substitute for thermal catalysis under mild conditions. However, the utilization of organic solvents and low faradaic efficiency are incompatible with the principles of green chemistry and energy conservation. Herein, bimetallic PtRu supported on carbon paper developed by co-electrodeposition with optimized atomic ratios maintains an inspiring high conversion of 92.9%, high selectivity of 100% and a high faradaic efficiency of 62.2% for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid in an acidic aqueous electrolyte without external H₂, which is the best result to date. The optimized electrocatalyst also exhibits outstanding stability and universality for the electrocatalytic hydrogenation of benzoic acid derivatives. In situ Raman results and theoretical calculations prove that the synergistic effect generated by Ru modifying the electronic structure of Pt simultaneously enhances the capture of benzoic acid molecules and interfacial active hydrogen species and lowers the reaction energy barrier. After adsorbing benzoic acid, more accumulation of electrons around the Ru atom reduces the electron density of phenyl, thereby activating the reaction. Meanwhile, the uniform alloy nanoclusters anchored to the carbon paper surface ensure highly efficient electronic transmission and high dispersion of active components, reducing excessive agglomeration. A proton-exchange membrane reactor is also used to certify the potential of the electrocatalytic hydrogenation of benzoic acid derivatives for large-scale application.