Selective Reduction of Phenol to Cyclohexanone with Electron Mediators via Off-Field Electrocatalysis

Electrocatalytic hydrogenation offers a promising approach for biomass upgrading under mild conditions, yet its performance is often compromised by mass and electron transfer limitations, particularly at high current densities. Here, we introduce an off-field electrocatalytic (OFEC) system that uses V2+/V3+ as electron mediators to reduce phenol, a representative biomass derivative, into cyclohexanone over Pt/TiO2 catalysts, effectively decoupling the reaction from the electrode surface. This fluidized strategy delivers a 10-fold increase in turnover frequency (TOF) compared to that of the conventional electrocatalysis (3090 vs 290 h–1) while maintaining 94% cyclohexanone selectivity, underscoring the alleviation of transport bottlenecks. Crucially, Pt/TiO2 effectively suppresses the secondary adsorption of cyclohexanone, thereby enhancing targeted selectivity. Furthermore, mechanistic studies reveal that electron transfer between mediators and phenol proceeds via a metal-mediated proton-coupled electron transfer (PCET) mechanism, enabling direct electron exchange at active sites while avoiding the poor conductivity of TiO2. Together, these findings establish a reaction paradigm for phenol hydrogenation at high current densities and provide a versatile platform for sustainable electrocatalytic biomass valorization.