LED-driven controlled deposition of Ni onto TiO(2) for visible-light expanded conversion of carbon dioxide into C(1)–C(2) alkanes

Photocatalytic gas-phase hydrogenation of CO(2) into alkanes was achieved over TiO(2)-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 TiO(2) P25 nanoparticles in methanol as a hole scavenger. This procedure yielded 2 nm Ni particles decorating the surface of TiO(2) with a nickel mass content of about 2%. Before the photocatalytic runs, Ni/TiO(2) was submitted to thermal reduction at 400 °C in a 10% H(2) atmosphere which induced O-defective TiO(2−x) substrates. The formation of oxygen vacancies, Ti(3+) centers and metallic Ni sites upon photocatalytic CO(2) 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 CO(2) below 300 °C to yield CO, CH(4) and C(2)H(6) as final products.