Surface-State-Driven Selectivity of Electrocatalytic Glucose Oxidation: Metallic Au, Au─OH, and CuO

The electrochemical glucose oxidation reaction (GLUOR) offers a sustainable route for biomass valorization, yet its reaction mechanisms and the factors governing product selectivity remain poorly understood. Herein, we present a comprehensive mechanistic investigation of GLUOR on Au and CuO catalysts. Au catalysts preserve the C6 carbon backbone while exhibiting surface-state-dependent oxidation of terminal functional groups of glucose (GLU), whereas CuO catalysts preferentially promote C─C bond cleavage reactions. Theoretical investigation reveals that C─C bond cleavage is energetically unfavorable on Au surfaces, in either the metallic or the hydroxylated state, but it is thermodynamically preferred on CuO surfaces. Furthermore, we provide spectroscopic and computational evidence that pyranose glucose undergoes ring opening on metallic Au surfaces, while ring-retained pathways dominate on Au─OH and CuO surfaces, leading to gluconolactone formation and C─C bond cleavage, respectively. These findings provide a fundamental framework for interpreting product selectivity in glucose oxidation and offer mechanistic insights applicable to a broad range of biomass valorization processes.