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

Abstract

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-Ti³⁺ dual-active sites in TiO₂, 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 H₂ formation, while Ti³⁺ 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.