Photothermo-catalytic strategies for the CO2 valorisation using TiO2-based composites

Two different multi catalytic approaches were here investigated to valorise the CO2. The first was the thermo-assisted solar photocatalysis applied for the CO2 conversion into CO and CH4, the second was the solar photo-assisted thermocatalysis for the CH4 and CO2 conversion into syngas (dry reforming). For the first reaction a low content of TiO2 (10 wt%) was deposited on several zeolites to expose the TiO2 surface-active sites to the simulated solar radiation. The best sample (0.5 wt% Cu2O/TiO2-mordenite) gave the 65% of CO2 conversion at 120 °C with the formation of 12 μmolCO/gcat·h and 4 μmolCH4/gcat·h. The Cu2O co-catalyst, favoured the charge carriers separation, generated on TiO2, to efficiently convert the CO2 adsorbed on the mordenite basic sites. Conversely, for the dry reforming an opposite strategy was adopted (the photo-assisted thermocatalysis) using Pd (0.3 wt%)-Ni (2% wt)/TiO2. The exploitation of the visible part of the solar radiation promoted by the Ni-Pd sites led to the decrease of the activation energy (Ea) (the EaCO and the EaH2 decreased from 29 and 27 kJ/mol of the thermocatalysis to 23 kJ/mol for both the products of the photo-assisted thermocatalysis) and to increase the CO2/CH4 conversion at lower temperature, 500 °C, instead of the 600 °C usually required. These new strategies with easy-to-prepare catalysts are promising to improve the solar fuels formation from the CO2.