Cooperation of Strong Electric Field and H2O Dissociation on Co3O4-Decorated SiC Rods for Photodriven CO2 Methanation with 100% Selectivity.

ABSTRACT

Solar-driven methanation of carbon dioxide (CO2) with water (H2O) has emerged as an important strategy for achieving both carbon neutrality and fuel production. The selective methanation of CO2 was often hindered by the sluggish kinetics and the multiple competition of other C1 byproducts. To overcome this bottleneck, we utilized a biomass synthesis method to synthesize SiC rods and then constructed a direct Z-scheme heterojunction Co3O4/SiC catalyst. The substantial difference in work functions between SiC and Co3O4 served as a significant source of the charge driving force, facilitating the conversion of CO2 to CH4. The high-valent cobalt Co(IV) in Co3O4 acts as an active species to promote efficient dissociation of water. This favorable condition greatly enhanced the likelihood of a high concentration of electrons and protons around a single site on the catalyst surface for CO2 methanation. DFT calculation showed that the energy barrier of CO2 hydrogenation was significantly reduced at the Co3O4/SiC heterojunction interface, which changed the reaction pathway and completely converted the product from CO to CH4. The optimum CH4 evolution rate of Co3O4/SiC samples was 21.3 µmol g-1 h-1 with 100% selectivity. This study has an important guiding significance for the selective regulation of CO2 to CH4 products in photocatalysis applications.