Effects of Carbon Supports on Ru Electrocatalysis for the Electrohydrogenation of Toluene to Methylcyclohexane

Electrochemical hydrogenation of toluene (TL) to methylcyclohexane (MCH) using a polymer electrolyte membrane electrolysis cell (PEEC) has been paid attention for application to hydrogen storage system. Although a 50 wt% Pt/Ketjenblack (KB) electrocatalyst was active for the electrohydrogenation of TL, we have found that KB supported only 1 wt% Ru electrocatalyst (Ru/KB) which was active for the electrohydrogenation. In this work, effects of carbon support on Ru electrocatalysis for the electrohydrogenation were investigated. Electrohydrogenation activities of Ru using various carbon materials, carbon blacks, graphenes, and carbon fiber were evaluated, and strong carbon-support effects were observed. Carbon black-supported Ru cathodes showed superior electrohydrogenation activities to compare with that of graphene or carbon fiber-supported Ru cathodes. A Black Pearls® 3500 supported Ru (Ru/BP3500) cathode showed an especially high electrohydrogenation activity even at a higher current density of 400 mA cm −2 in galvanostatic electrolysis. The Ru/carbon materials were characterized by N 2 adsorption, X-ray diffraction (XRD), high-angle annular dark-field scanning transmitting electron microscope (HAADF-STEM), CO-pulse adsorption, and X-ray photoelectron spectroscopy (XPS). These characterization data indicated that Ru particle sizes and Ru surface areas of cathodes were very similar though their electrocatalytic activities were different. Effects of the carbon supports on the electrohydrogenation were discussed on a basis of the reaction mechanism reported previously. Graphical Abstract A 1 wt% Ru/carbon-black (BP-3500) cathode shows excellent electrocatalytic activity for electrohydrogenation of toluene to methylcyclohexane.