Electrochemical oxidation of glycerol to hydroxypyruvic acid on cobalt (oxy)hydroxide by high-valent cobalt redox centers

Transforming glycerol to value-added chemicals by mild electrochemical oxidation on earth-abundant, low-cost transition metal electrocatalysts is both environmentally and economically beneficial. Herein, substoichiometric cobalt (oxy)hydroxide CoOxHy has been demonstrated as an effective electrocatalyst for selective glycerol oxidation to hydroxypyruvic acid (HPA), an important chemical intermediate with three carbon atoms bearing three different functional groups. The Faradaic efficiency for HPA production can reach 43.2%, with an average production rate of 679.2 µmol min−1 mgeo−2. Through systematic investigation using cyclic voltammetry, step potential electrochemical spectroscopy, and in situ Raman spectroscopy characterizations, we have revealed that the high-valent cobalt center is responsible for the enhanced activity and selectivity, where electrochemically more stable CoOx exhibits much lower activity and Faradaic efficiency in comparison. This redox-mediated glycerol oxidation mechanism offers a new perspective for future electrocatalyst development toward selective glycerol valorizations.