Constructing Asymmetric Defects Pairs in Electrocatalysts for Efficient Glycerol Oxidation

Disrupting the charge distribution equilibrium in catalysts is an effective strategy for the polarization and cleavage of small molecules during the electrocatalytic process. To achieve effective C-C bond cleavage in multicarbon molecules, such as glycerol, integrating the advantages of defect sites while creating spatially asymmetric sites that modulate the local electronic perturbations is both promising and challenging. In this study, spatially asymmetric defect pairs were engineered by partially refilling sulfur atoms into spinel CuCo₂O_x with a high oxygen vacancy density (H_Vo-S). These oxygen defect-refilled S pairs (Vo-S) enhance the local charge transfer, reduce the energy barrier for glycerol adsorption, and create thermodynamically favorable conditions for the second C-C bond cleavage, whereas the high density of oxygen vacancies further amplifies the local electronic perturbations. Exploiting the spatial effects of asymmetric defect sites, H_Vo-S demonstrated superior performance compared to H_Vo without Vo refilling, achieving Faradaic efficiencies (FE) of 98.5% and 75.3% at 1.36 V vs RHE for formic acid in the glycerol oxidation reaction (GOR), respectively. Significantly, this strategy also promotes C-C bond cleavage during the electrooxidation of ethylene glycol and glucose, further confirming its broad applicability in activating C-C bonds in polyol substrates. This study elucidates the role of the spatial effects of localized asymmetric defect sites in the GOR process, providing new insights for the design of novel electrocatalysts aimed at promoting C-C bond cleavage in polyol molecules.