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

Abstract

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 TiO2 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 Ti3+/Ti4+ redox pair plays an important role in the reduction of oxalic acid.

Highly Efficient Electrosynthesis of Glycine over an Atomically Dispersed Iron Catalyst

“…NO 2 – is the main product of NO 3 – RR over the N–C-700 catalyst, which indicates that the Fe–N configuration is crucial for producing NH 2 OH to realize the C–N coupling. As mentioned above, GX is the key intermediate in the process of glycine formation; however, it can be over-reduced to GC. , During the OARR, production of GX suppresses that of GC at −0.9 V versus RHE over the N–C-700 catalyst (Figure S20). In contrast, N–C-600 with a lower pyrrolic N content of 2.49 atom % (Figure S21) exhibits a lower FE GX than N–C-700 (Figure S22), evincing that a rich pyrrolic N content could facilitate the OARR to GX.…”

“…From an economic perspective, using upstream carbonaceous molecules as reactants could offer a cost-competitive route for amino acid production with a reduced number of chemical production steps. Oxalic acid (OA) is a highly electrochemical reactive reagent , and could be obtained from CO 2 or biomass transformation, such as CO 2 electroreduction and glucose oxidation . OA can be selectively electro-reduced to GX, , which could further react with NH 2 OH to produce glycine. , However, this C–N coupling process involves multiple electron and proton transfer steps, which increases the possibility of side reactions, thus decreasing the selectivity toward glycine.…”