Pt-Cu@Bi₂MoO₆/TiO₂ Photocatalyst for CO₂ Reduction

Bi₂MoO₆/TiO₂ heterojunction photocatalysts were constructed by depositing Bi₂MoO₆ nanosheets on TiO₂ nanobelts' surface using a solvothermal method, and the surface of the optimum Bi₂MoO₆/TiO₂ composite was decorated with copper and/or platinum nanoparticles. The synthesized samples were investigated for the CO₂ photocatalytic reduction. The structural and optical properties of synthesized photocatalysts were characterized by XRD, FESEM, EDX, N₂-physisorption, Raman, TPD-CO₂, DRS, and PL analysis. The Bi₂MoO₆/TiO₂ composite with different molar ratios of Bi₂MoO₆ to TiO₂ (1, 1/2, 1/3, 1/4, 1/5, and 1/6) showed enhanced photocatalytic activity compared to pure Bi₂MoO₆ and TiO₂. In comparison to bulk Bi₂MoO₆ and TiO₂, the formation of a heterojunction between Bi₂MoO₆ and TiO₂ leads to enhanced CO₂ adsorption capacity. The enhanced performance of composites can be ascribed to the improved efficiency of light harvesting in the visible light range and suppressing charge recombination. The composite photocatalytic activity indicated that the ratio of Bi₂MoO₆ to TiO₂ in the composite samples influenced the photocatalytic performance. The Bi₂MoO₆/TiO₂ composite with 1/4 molar ratio had the best performance in 8 h (36.4 μmol/g_cat), which was about 10 and 3 times higher than TiO₂ and Bi₂MoO₆ photocatalysts, respectively. Under UV-visible light irradiation, the Pt-Cu@BMT4 sample produced the highest amount of methane (83.6 μmol/g_cat) during CO₂ photoreduction. During four irradiation cycles, the Pt-Cu@BMT4 sample exhibited superior stability with less than 5% decrease in methane production.