Synthesis and characterization of Cu–Zn/TiO₂ for the photocatalytic conversion of CO₂ to methane

Different Cu–Zn/TiO₂ catalysts were synthesized by using the wet impregnation method. The prepared catalysts were used for the conversion of CO₂ into methane by photocatalysis. Various characterization techniques were used to observe the surface morphology, crystalline phase, Brunauer–Emmett–Teller (BET) surface area, presence of impregnated Cu and Zn, and functional group. Scanning electron microscope analysis showed spherical morphology, and slight agglomeration of catalyst particles was observed. BET analysis revealed that the surface area of the catalyst was decreased from 10 to 8.5 m²/g after impregnation of Cu and Zn over TiO₂ support. Synergetic effect of Cu and Zn over TiO₂ support (Cu_2.6/TiO₂, Zn_0.5/TiO₂ and Cu_2.6–Zn_0.5/TiO₂) and the effects of Cu loading (0, 1.8, 2.1, 2.6 and 2.9 wt%) were also investigated at different feed molar ratios of H₂/CO₂ (2:1 and 4:1). The Cu_2.6–Zn_0.5/TiO₂ catalyst showed a maximum conversion of 14.3% at a feed molar ratio of 4. The addition of Zn over the catalyst surface increased the conversion of CO₂ from 10% to 14.3% which might be due to synergy of Cu and Zn over TiO₂ support.