LED-driven controlled deposition of Ni onto TiO2 for visible-light expanded conversion of carbon dioxide into C1–C2 alkanes

Abstract

Photocatalytic gas-phase hydrogenation of CO₂ into alkanes was achieved over TiO₂-supported Ni nanoparticles under LED irradiation at 365 nm, 460 nm and white light. The photocatalysts were prepared using photo-assisted deposition of Ni salts under LED irradiation at 365 nm onto TiO₂ P25 nanoparticles in methanol as a hole scavenger. This procedure yielded 2 nm Ni particles decorating the surface of TiO₂ with a nickel mass content of about 2%. Before the photocatalytic runs, Ni/TiO₂ was submitted to thermal reduction at 400 °C in a 10% H₂ atmosphere which induced O-defective TiO_2−x substrates. The formation of oxygen vacancies, Ti³⁺ centers and metallic Ni sites upon photocatalytic CO₂ hydrogenation was confirmed by operando EPR analysis. In situ XPS under reaction conditions suggested a strong metal–support interaction and the co-existence of zero and divalent Ni states. These photoactive species enhanced the photo-assisted reduction of CO₂ below 300 °C to yield CO, CH₄ and C₂H₆ as final products.