Fabricating an ohmic junction of Ag/CdS for highly efficient multi-electron reduction of CO2 to CH4

Photocatalytic reduction of CO₂ to chemical fuels is a promising strategy to alleviate the greenhouse effect and energy crisis. This article successfully fabricated Ag/CdS composites with ohmic junction using a two-step method and further verified them by DFT calculations. Meanwhile, photoelectrochemical and electron paramagnetic resonance tests show that Ag/CdS has higher photocurrent density and lower charge transfer resistance, suggesting that the ohmic junction achieves ultrafast electron transfer from CdS to Ag under light irradiation, significantly promoting the separation of photogenerated carriers. Furthermore, the localized plasmon resonance (LSPR) of Ag enhances the light absorption of the catalyst and generates a large number of hot electrons for the photocatalytic reduction reaction. The synergistic effect of ohmic junction and LSPR gives high electron density at the reaction site, which promotes the multiple proton-coupled electron reactions leading to highly selective photoconversion of CO₂ to CH₄. Under the optimized conditions, the CH₄ yield of the synthesized Ag/CdS is 68.6 μmol·g⁻¹·h⁻¹, which is 25.4 times higher than that of bare CdS, and the CH₄ selectivity increases from 53.8 % to 90.1 %. This study provides a new idea for the design of CdS-based materials for highly selective reduction of CO₂ to CH₄.