Electrochemical hydrogenation of non-aromatic carboxylic acid derivatives as a sustainable synthesis process: from catalyst design to device construction.

Electrochemical hydrogenation of a carboxylic acid using water as a hydrogen source is an environmentally friendly synthetic process for upgrading bio-based chemicals. We systematically studied electrochemical hydrogenation of non-aromatic carboxylic acid derivatives on anatase TiO2 by a combination of experimental analyses and density functional theory calculations, which for the first time shed light on mechanistic insights for the electrochemical hydrogenation of carboxylic acids. Development of a substrate permeable TiO2 cathode enabled construction of a flow-type electrolyser, i.e., a so-called polymer electrode alcohol synthesis cell (PEAEC) for the continuous synthesis of an alcoholic compound from a carboxylic acid. We demonstrated the highly efficient and selective conversion of oxalic acid to produce glycolic acid, which can be regarded as direct electric power storage into an easily treatable alcoholic compound.