Wood Carbon-Enabled Metal Vacancies Drive Electrochemical Hydrogenation: Selective CO2 Methanation and Beyond.

Electrochemical hydrogenation (ECH) demands precise control over multistep pathways, yet developing selective electrocatalysts remains challenging. Herein, we utilize hierarchical carbonized wood (CW) as a sustainable catalytic support to drive deep ECH reactions. By anchoring ZnO nanosheets within CW's microchannels via facile calcination-impregnation, we engineered ZnO/CW catalysts enriched with Zn and O vacancies that promote CO2 deep hydrogenation to CH4. By coupling ZnO/CW and 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6)/acetonitrile electrolyte, the system exhibited high CH4 Faradaic efficiency (FE) of 72.9% at -1.34 V vs. SCE. This performance fundamentally diverged from conventional ZnO/carbon paper (ZnO/CP) which terminates at CO production (62.3% FE), showcasing support-driven pathway redirection. Both experimental and theoretical investigations revealed that CW's porous framework facilitates mass transport while Zn vacancies lower the energy barrier in the CH4 pathway. The platform's versatility extended to oxalic acid upgrading, where SnO2/CW achieved selective ECH of oxalic acid to glycolic acid in identical electrolytes. This work establishes biomass-derived defect-rich interfaces as sustainable design paradigm for multistep electrocatalytic hydrogenations.