Photocatalytic hydrocarbon production from aqueous acetic acid using TiO2 with simultaneous photodeposition of Cu†

Photocatalytic techniques are considered clean, sustainable and cost-effective in energy conversion and environmental restoration. The large band gap, light harvesting limitation and rapid electron–hole pair recombination can suppress the photocatalytic efficiency in photocatalytic applications. Metal deposition has become one of the most important technical means to improve photocatalytic efficiency. This study has dealt with photocatalytic hydrocarbon and hydrogen production from the acetic acid solution with simultaneous in situ Cu deposition on TiO₂ photocatalyst surface. Due to having favorable redox potential and work function values, the photodeposition and Schottky junction formation of Cu occurred smoothly on the TiO₂ surface, which further contributed to accelerating the interfacial charge transfer and photocatalytic activity. The reaction conditions (Cu²⁺ loading, reaction pH and initial concentration of acetic acid) were optimized to enhance photocatalytic methane production. Under the optimum condition, the Cu/TiO₂ photocatalytic hydrocarbon production was maximum (4136 μmol g⁻¹), approximately 9 times better than those obtained with pure TiO₂ (450 μmol g⁻¹). The surface morphological and optical properties of photodeposited Cu/TiO₂ samples were characterized before and after the photocatalytic reaction with utmost precision and thoroughness using a TEM, XPS, DRS, PL, N₂ adsorption–desorption isotherm and BET surface area analysis. The DRS and PL study confirm that in situ Cu-deposition on TiO₂ reduced the energy bandgap and improved the light-harvesting area, photogenerated electron–hole pair separation and migration efficiency, respectively. Cycle experiments disclose that the simultaneous Cu-deposited photocatalyst has excellent stability and reusability. A reaction mechanism was proposed for the photocatalytic hydrocarbon formation from the acetic acid by Cu/TiO₂ photocatalytic reaction.