Electrochemical conversion of oxalic acid to glycolic acid via oxygen vacancy–mediated tandem catalysis

The electrochemical conversion of oxalic acid (OX) to glycolic acid (GC) offers a sustainable route for biomass valorization yet suffers from inefficient proton-coupled electron transfer and competitive hydrogen evolution. We report an oxygen vacancy (O V )–mediated atomic interface strategy to construct Fe δ- -O V -Ti 3+ dual-active sites in TiO 2 , enabling tandem activation of H + and C═O bond through a (2e − + 2e − ) relay mechanism. The Fe-TiO X /titanium paper electrocatalyst achieves a faradaic efficiency of 74.3% with >60% GC selectivity at industrially relevant current densities (~100 milliamperes per square centimeter), stable for ~60 hours, which is a record high in electrochemical conversion of OX to GC. In situ spectroscopy and density functional theory calculations reveal that the Fe δ- sites dynamically stabilize H* intermediates while inhibiting H 2 formation, while Ti 3+ sites form a σ─π coordination bond with the carbonyl oxygen in OX, lowering the energy barrier of the rate-determining step. This work provides a paradigm for designing a dual site in electrochemical tandem reactions, offering fundamental insights in sustainable chemical synthesis.