Electrosynthesis of H2O2 to Drive an Electrochemical−Chemical Cascade Process for Pyruvic Acid Preparation

The in-situ electrochemical generation of H2O2 via the two-electron oxygen reduction reaction (2e−ORR) offers an attractive pathway for coupling the efficient production of oxidants with biomass conversion. However, the overall efficiency of such electrochemical−chemical cascade systems is typically limited by insufficient H2O2 selectivity and unclear subsequent activation mechanisms. In this study, nitrogen-doped carbon catalysts were constructed for the efficient in-situ generation of H2O2 via 2e−ORR, followed by coupling with the selective oxidation of lactic acid to produce pyruvic acid. The sample subjected to heat treatment at 500 °C (C−500) exhibited the highest performance among the investigated C−T catalysts. In 0.1 M KOH, it achieved an H2O2 yield of 14.1 mol g−1 h−1 with a faradaic efficiency of 98.4%, maintaining nearly 100% selectivity across a wide potential range. In the lactic acid oxidation cascade system, it achieved a pyruvic acid yield of 12.5 mmol g−1 h−1 with a faradaic efficiency of 48.7%. Mechanistic studies revealed that the synergistic regulation of pyridinic nitrogen and carbonyl groups (C=O) optimizes the adsorption of the *OOH intermediate and suppresses O−O bond cleavage, thereby promoting the high-selectivity 2e−ORR pathway. Furthermore, the in situ-generated H2O2 was effectively activated during the subsequent oxidation process, forming a reactive oxygen species network involving hydroxyl radicals (·OH), superoxide radicals (·O2−), and singlet oxygen (1O2). Among them, ·OH plays a key role in the activation of the α-C−H bond of lactic acid, while other reactive oxygen species synergistically promote the subsequent oxidation process. This work establishes a structure−reaction correlation mechanism from in situ H2O2 generation and activation to selective oxidation of biomass molecules, providing a design strategy for high-value biomass conversion driven by in-situ oxidants.