(410g) Bringing Rationality into the Development of Low Cost and Active Photocatalyst for CO2 Conversion to Methanol - Bridging Experiments and First-Principles Calculations

Photocatalytic CO₂ conversion to methanol is demanding for sustainability. Thermochemical processes are energy intensive and often associated with harsh reaction conditions. An economical alternative could be photochemical route which asks for efficient photocatalyst having attributes of ease of electron transfer across metal oxide interface, lower recombination rate and higher CO₂ activation. The present study is focused on (i) tweaking properties of base photocatalysts TiO₂ and ZnO by performing synthesis, in-depth characterization and activity experiments, and (ii) developing property-activity correlation to guide catalyst formulation. Here, CuO was chosen due to its narrow band gap and being p-type semiconductor was beneficial to create heterojunctions with n-type TiO₂ and ZnO. We anticipate that this might promote the charge separation efficiency along with the creation of surface oxygen vacancy facilitating the CO₂ reduction pathways. Finally, experimental and First-Principles calculations results were correlated to establish structure-activity relationships.

Both CuO/TiO₂ and CuO/ ZnO heterostructure catalysts were fabricated impeccably, and during photoinduced reactions, both yielded additional methanol compared to TiO₂ and ZnO, respectively, implying successful creation of heterojunction photocatalysts. The higher yield of CuO/TiO₂ than CuO/ZnO demonstrated that TiO₂ is a prominent choice than ZnO due to more narrowing of band gap, better charge separation and lower recombination rate. Finally, methanol yield rate when correlated with separation efficiency and average electron lifetime, it produced almost linear dependency, which are representative of structure-activity relationships. Moreover, the increased oxygen vacancy by adding CuO enabled more CO₂ activation, leading to higher photo-reactivity. Therefore, this study delved into improved understanding on the intrinsic properties of the photocatalysts from experimental characterization and theoretical calculations and finally used them to explain the activity trend. Overall, this approach marks as a rationalised way forward for exploring efficient methanol forming catalysts by photocatalytic CO₂ reduction.