Highly Selective Electrooxidation of Glycerol to Tartronic Acid Over a Single-Atom Rhodium Catalyst Supported on...

The electrooxidation of biodiesel-derived glycerol offers an effective approach for the sustainable production of valuable C₃ compounds. However, highly selective synthesis of a specific C₃ compound, such as tartronic acid (TA), by glycerol electrooxidation remains a big challenge due to the competitive dehydrogenation between C_αH₂(OH) and C_βH(OH). Herein this study reports a glycerol electrochemical oxidation reaction (GEOR) for the selective production of TA, which is catalyzed by a single-atom rhodium catalyst supported on indium oxide (Rh₁-In₂O₃) in an alkaline medium. At a potential of 1.40 V versus reversible hydrogen electrode, the Rh₁-In₂O₃-catalyzed GEOR achieves an optimal TA selectivity of 93.2% and a productivity of 4.6 mmol cm^-2 h^-1, outperforming all previously reported electrocatalytic systems for the GEOR. Experimental results, complemented by density functional theory calculation, reveal that the single-atom Rh catalyst improves glycerol oxidation by facilitating hydroxyl oxidation to active oxygen species and greatly decreasing the energy barrier for C_αH₂(OH) dehydrogenation in the GEOR process, thus resulting in high TA selectivity. Furthermore, an integrated electrolyzer, combining GEOR with the hydrogen evolution reaction, achieves a current density of 100 mA cm^-2 at a cell voltage of 1.50 V. A techno-economic analysis demonstrates the economic feasibility of this integrated system.