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.