The selective production of CH4via photocatalytic CO2 reduction over Pd-modified BiOCl

Abstract

Photocatalytic CO₂ reduction to CH₄ is a promising strategy for converting the main greenhouse gas CO₂ to achieve a future with net-zero emissions. However, efficient photocatalysts with high selectivity are still far from being applied. In the present work, we reported BiOCl nanosheets loaded with noble metals (Au, Ag, Pt, or Pd), fabricated via a facile photodeposition method, for photocatalytic CO₂ reduction. Among these metals, Pd-loaded BiOCl (Pd/BiOCl) with 1.0 wt% loading showed the highest activity and best selectivity toward CH₄ formation. The enhancements in activity and selectivity were further studied by investigating the photogenerated electron–hole separation efficiency and surface intermediate pathways during photocatalytic CO₂ reduction. It was found that Pd-loaded BiOCl could effectively decrease the recombination of electrons and holes and improve the photocurrent density during light irradiation. Furthermore, surface CO₂ adsorption studies based on in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) implied that bicarbonates rather than carbonates were the main species on Pd/BiOCl under dark conditions. These species were increased and further transformed to bidentate formate and methoxy as key intermediates during CH₄ formation. The enhanced charge separation efficiency and formation of bidentate formate and methoxy on Pd/BiOCl promoted the CH₄ activity and selectivity during photocatalytic CO₂ reduction. Our work provides a facile and efficient way to achieve photocatalytic CO₂ reduction for the selective formation of CH₄.