Modulating the Coverage of Adsorbed Hydrogen via Hydrogen Spillover Enables Selective Electrocatalytic Hydrogenation of Phenol to Cyclohexanone

Selective electrocatalytic hydrogenation (ECH) of phenol is a sustainable route to produce cyclohexanone, an industrially important feedstock for polymer synthesis. However, attaining high selectivity and faradaic efficiency (FE) for cyclohexanone remain challenging, owning to over-hydrogenation of phenol to cyclohexanol and competition of hydrogen evolution reaction (HER). Herein, by employing hydrogen spillover effect, we modulate adsorbed hydrogen species (H_ads) coverage on Pt surface via migration to TiO₂ in an anatase TiO₂-supported Pt catalyst. In ECH of phenol, a high selectivity (94 %) and good FE (63 %) for cyclohexanone are obtained, showing more advantageous performance compared with previous reports. Cyclic voltammetry (CV) tests and electrochemical Raman spectroscopy reveal that H_ads migrated from Pt to TiO₂. We propose that TiO₂-induced hydrogen spillover contributes to low H_ads coverage over Pt, which effectively hinders over-hydrogenation of cyclohexanone and HER. We establish a scaling relationship between the intensity of hydrogen spillover and cyclohexanone selectivity by varying the types of anatase TiO₂, and show the universality of the strategy over other reducible metal oxides as the support (rutile TiO₂, CeO₂ and WO₃). This work showcases an effective strategy for tuning hydrogenation selectivity in electro-catalysis, by taking advantage of thermo-catalytically well-documented hydrogen spillover effect.