Controlling the selectivity of high-surface-area Ru/TiO2 catalysts in CO2 reduction - modifying the reaction properties by Si doping of the support.

The influence of Si doping of high specific-surface-area Ru/TiO 2 catalysts with similar structural properties on the CO 2 reduction reaction was systematically investigated by kinetic measurements, combined with microscopic and spectroscopic methods for ex situ and in situ / operando catalyst characterization. While for undoped Ru/TiO 2 a high-temperature treatment (350 °C) in reaction atmosphere results in a pronounced change of the selectivity from methanation to CO formation via the reverse water-gas shift (RWGS) reaction, CH 4 formation is stabilized by Si doping of the catalyst support. For doping levels around 8 wt%, almost 100% CH 4 selectivity is maintained. Comprehensive catalyst characterization is employed to identify trends in the physical and chemical properties with increasing Si doping and thus physical reasons responsible for the distinct differences in catalyst performance and stability. This work opens a route for improving the stability and selectivity of Ru/TiO 2 catalysts in the CO 2 hydrogenation reaction, a highly relevant application. [Display omitted] • High-surface-area (SSA) Ru/TiO 2 catalysts are highly active for CO 2 hydrogenation. • High-SSA Ru/TiO 2 catalysts are 100% selective for methane formation. • This high selectivity breaks down after temperature excursions during reaction. • Si doping stabilizes selectivity of high-SSA Ru/TiO 2 catalysts for CO 2 methanation. • Catalyst characterization reveals complex origin of the thermal stabilization. [ABSTRACT FROM AUTHOR]