The electrocatalytic hydrogenation of o-xylene in a proton-exchange membrane (PEM) reactor with various cathode catalysts was carried out as a study of a model reaction for hydrogen storage. o-Xylene introduced in a PEM reactor underwent electrocatalytic hydrogenation to provide cis-1,2-dimethylcyclohexane as the main stereoisomer with moderate to good current efficiencies. The reaction proceeded in accordance with the Langmuir-Hinshelwood mechanism.