Insight into the role of UV-irradiation in photothermal catalytic Fischer–Tropsch synthesis over TiO2 nanotube-supported cobalt nanoparticles†
To explore an efficient catalytic system with high activity and selectivity is the key to improve Fischer–Tropsch synthesis (FTS) technology and the main focus in the academic field. Herein, a photothermocatalytic system for FTS was constructed by combining thermo-active components with photosensitive supports. 20 wt% and 30 wt% Co supported on TiO2 nanotube (TNT) catalysts were prepared through an incipient wetness impregnation method (named 20% Co/TNT and 30% Co/TNT) and were applied to a photothermocatalytic process to investigate the role of ultraviolet (UV) illumination in the traditional thermochemical FTS reaction. The results indicated that the introduction of UV light dramatically improved CO conversion, from 9.2% to 64.0% for 20% Co/TNT and from 8.6% to 17.1% for 30% Co/TNT. In addition, UV illumination gave rise to an increase in light paraffin selectivity. The improvement of CO conversion was found to be related to the photogenerated electron transfer from TNTs to active Co sites upon UV light irradiation, which caused the Co sites to have increased surface electron density and subsequently enhanced the adsorption and activation of CO molecules at Co sites. Meanwhile, the increase in light paraffin selectivity was attributed to the photo-promoted hydrogenation of olefin and the hydrogenolysis of the long-chain hydrocarbons. The present work promoted a deeper understanding of the photothermal FTS reaction mechanism and demonstrated that photothermocatalysis could have potential for enhancing FTS catalytic performance and adjusting product distribution.