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)-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.