The reaction mechanism of reverse water-gas shift (RWGS) reaction was investigated using two commercial gold-based catalysts supported on Al2O3 and TiO2. The surface species formed during the reaction and reaction mechanisms were elucidated by transient and steady-state operando DRIFTS studies. It was revealed that RWGS reaction over Au/Al2O3 proceeds through the formation of formate intermediates that are reduced to CO. In the case of Au/TiO2 catalyst, the reaction goes through a redox mechanism with the suggested formation of hydroxycarbonyl intermediates, which further decompose to CO and water. The Ti3+species, the surface hydroxyls, and oxygen vacancies jointly participate. The absence of carbonyl species adsorbed on gold particles during the reaction for both catalysts indicates that the reaction pathway involving dissociative adsorption of CO2 on Au particles can be discarded. To complete the study Operando UV-Vis spectroscopy was successfully applied to confirm the presence of Ti3+ and to understand the role of the oxygen vacancies of TiO2 support in activating CO2 and thus the subsequent RWGS reaction.

Carbon formation and sintering remain the main culprits regarding catalyst deactivation in the dry and bireforming\ud of methane reactions (DRM and BRM, respectively). Nickel based catalysts (10 wt.%) supported on\ud alumina (Al2O3) have shown no exception in this study, but can be improved by the addition of tin and ceria. The\ud effect of two different Sn loadings on this base have been examined for the DRM reaction over 20 h, before\ud selecting the most appropriate Sn/Ni ratio and promoting the alumina base with 20 wt.% of CeO2. This catalyst\ud then underwent activity measurements over a range of temperatures and space velocities, before undergoing\ud experimentation in BRM. It not only showed good levels of conversions for DRM, but exhibited stable conversions\ud towards BRM, reaching an equilibrium H2/CO product ratio in the process. In fact, this work reveals how\ud multicomponent Ni catalysts can be effectively utilised to produce flexible syngas streams from CO2/CH4 mixtures\ud as an efficient route for CO2 utilisation.Peer reviewe