Hydrogenation of oxalic acid using light-assisted water electrolysis for the production of an alcoholic compound

We demonstrate the production of glycolic acid, an industrially important alcoholic compound, via the electrochemical reduction of oxalic acid, which is procurable from biomass, and electro-oxidation of water with the help of renewable light energy for the first time. In principle, this new synthesis system is achievable while minimizing the consumption of fossil resources. We built a precious-metal free electrosynthesis system by employing a TiO₂ cathode for oxalic acid reduction and a WO₃ photoanode for water oxidation. The alcohol production proceeds during the application of electric power above 2.1 V in the dark. Notably, UV-visible light irradiation of the WO₃ photoanode enables glycolic acid electrosynthesis above 0.5 V, which is lower (by 0.6 V) than the theoretical bias, i.e., 1.1 V. Glycolic acid electrosynthesis with an 80% high Faradaic efficiency was achieved on applying a bias of 1.5 V under UV-visible irradiation (λ > 300 nm).