First-principles study of photocatalytic CO₂ reduction reactions on a 2D ferroelectric surface

The importance of reducing CO₂ into value-added products is continuously increasing due to the severe outcomes of global warming. Since CO₂ is a highly stable and chemically inert molecule, the reduction reaction requires catalysts that have superior selectivity and efficiency; 2D ferroelectric materials (monolayer thick compounds with a spontaneous switchable electric polarization) are coming into sight as promising candidates. 2D materials are intensively studied due to their high surface-to-volume ratio and abundant reactive sites, while the controllable and switchable polarization in 2D ferroelectric materials is a way to overcome the Sabatier Principle by changing the surface reactivity. In this study, Density Functional Theory was used to investigate the ferroelectric properties in a family of 2D MXene materials. We then selected Y₂CO₂, a member with the photocatalytic ability and ferroelectric properties, as the catalyst, and calculated energies and pathways of CO₂ reduction reactions on its surface. Three reduction pathways leading to different C1 products (CO, formic acid, and methanol) were examined on the Y₂CO₂ surface. By tuning the direction of electrical polarization, we can control the stability of different intermediates and the selectivity of different products.