Bromide–Borate Coupling Enables Selective Electrochemical Oxidation of Glycerol to Dihydroxyacetone

ABSTRACT Selective electrochemical valorization of biodiesel‐derived glycerol is challenged by competing oxidation pathways that generate complex product mixtures. Here, we report a bromide–borate‐mediated indirect glycerol electrooxidation for selective dihydroxyacetone (DHA) production on carbon electrodes. Bromide is electrochemically converted into soluble oxidized bromine species that mediate homogeneous glycerol oxidation, whereas borate provides a weakly alkaline bromine‐speciation window and coordinates glycerol to bias C3‐product formation toward DHA. At identical pH, borate favored DHA formation, whereas phosphate shifted selectivity toward glyceric acid. Under optimized conditions using 100 mM glycerol and 100 mM KBr in 1 M borate buffer solution (pH 8.2), divided H‐cell electrolysis afforded DHA with 75% relative selectivity and high overall Faradaic efficiency (FE). Recirculating flow‐cell operation increased DHA selectivity to 80% while maintaining high overall FE, and one‐way flow‐cell achieved a DHA production rate of 1205 mmol m −2 h −1 .