Selective Electroreduction of Oxalic Acid to Glycolic Acid by Mesoporous TiO2 Spheres

Graphical Mesoporous TiO 2 spheres with large specific surface area were synthesized by a simple two-step method for the electrocatalytic reduction of oxalic acid. The maximum Faradaic efficiency for glycolic acid reached 73.9 % at −0.5 V at ambient temperature, exceeding most recently reported results. Reducing oxalic acid to glycolic acid electrochemically remains a significant challenge due to the high overpotential and low selectivity and stability. This study uses mesoporous TiO 2 spheres of anatase phase as catalysts to reduce oxalic acid to glycolic acid with low overpotential. The maximum Faradaic efficiency of glycolic acid reaches 73.9 % at −0.5 V vs RHE. The mesoporous structure not only increases the specific surface area, but also limits the escape of intermediate glyoxalic acid from the catalyst surface due to the space-limiting effect of the mesoporous channel, such that oxalic acid can be deeply reduced to glycolic acid. Moreover, a mechanism for oxalic acid reduction is proposed, and the Ti 3+ /Ti 4+ redox pair plays an important role in the reduction of oxalic acid.