Synthesis of Concentrated Methylcyclohexane as Hydrogen Carrier through Photoelectrochemical Conversion of Toluene and Water.

A photoelectrochemical (PEC) cell consisting of a Pt-loaded carbon black (Pt/C)-based membrane electrode assembly (MEA) and a particulate SrTiO3 photoanode effected selective PEC conversion of toluene and water into methylcyclohexane (MCH) at concentrations up to >99 vol %. This cell exhibited 100 % faradaic efficiency (FE) and 18 % incident-photon-to-current conversion efficiency (IPCE) at 320 nm without an external bias voltage in the PEC hydrogenation of pure toluene. It was also found that strong alkaline conditions are beneficial with the present MEA to suppress the competitive side reaction of hydrogen evolution, resulting in a high FE of 94 % even during MCH production from 1 vol % toluene in MCH. This study successfully demonstrated that the present PEC system is capable of producing concentrated MCH as a promising hydrogen carrier and that MCH production from toluene and water represents a means of artificial photosynthesis.