Crystal Phase-Mediated Ni–TiO2 Interface Engineering for Photothermocatalytic Fischer–Tropsch Synthesis of Multi-Carbon Hydrocarbons

The crystal phase of titanium dioxide (TiO2) has a significant influence on the physicochemical properties and catalytic activities of supported metal catalysts. Herein, we synthesized two catalysts consisting of metallic nickel dispersed on anatase- and rutile-phase TiO2 (a-TiO2 and r-TiO2) supports with a simple impregnation-reduction method and assessed their photothermocatalytic activity for CO hydrogenation. The Ni-loaded r-TiO2 (Ni-r-TiO2) catalyst achieved a CO conversion of 23.3% at a photothermal temperature of 180 °C, which was 5.7 times that of the Ni-loaded a-TiO2 (Ni-a-TiO2) catalyst; meanwhile, the Ni-r-TiO2 catalyst achieved an increased C2+ hydrocarbon selectivity of 73.0% compared with that of the Ni-a-TiO2 catalyst (50.1%). CO-temperature-programmed desorption (CO-TPD), CO pulse experiments, and apparent activation energies of CO revealed the improved CO adsorption and activation abilities of the Ni-r-TiO2 catalyst. In situ diffuse reflectance infrared Fourier transform spectra (in situ DRIFTS) disclosed that the Ni-r-TiO2 catalyst followed direct CO dissociation, which led to the formation of more CH2* intermediates, subsequently yielding C2+ hydrocarbons. This work provides insights into the support design for the preferential formation of value-added chemicals.