A strategy of Co doping in MgO to significantly improve the performance of solar-driven thermocatalytic CO2 reduction on Ru/Co-MgO

Dry reforming of CH4 (DRM) driven solely by solar light provides an attractive strategy for solving energy shortages and global warming. The strategy faces two challenges: so far, high fuel productivity and solar-to-fuel efficiency (η) can only be realized at high solar intensities (usually more than 192 kW m−2). Furthermore, coking side reactions are more favorable in thermodynamically, which can lead to catalyst deactivation. Herein, a new nanocomposite of Ru nanoparticles (NPs) loaded on Co-doped MgO with reactive oxygen species and a strong optical absorption throughout the entire solar spectrum (Ru/Co-MgO) is prepared. At relatively low solar intensity (73.2 kw m−2), the solar-driven DRM on Ru/Co-MgO achieves high production rates of CO (rCO, 80.01 mmol g-1 catalyst min−1) and H2 (rH2, 62.31 mmol g-1 catalyst min−1) with larger η of 26.1 %, which shows an increase of 1.3-fold in rCO, rH2 and η, while a 65-fold decrease in coking rate (rC) compared to a reference catalyst of Ru and Co NPs loaded on MgO (RuCo/MgO). The significant improvement in the catalytic performance stems from the involvement of reactive oxygen (–Co–O–Mg–) in Co-MgO for the oxidation of C* species as a rate-determining step of DRM, which enhances the catalytic activity and significantly inhibits coking. Additionally, the light not only promotes the reactions both of DRM on Ru NPs and strongly adsorbed CO2 on Co-MgO with C* species at the Ru/Co-MgO interface, but also facilitates the dissociation of CO2 adsorbed on the oxygen vacancies of Ru/Co-MgO into CO, thus accelerating the synergistic effect between Ru NPs and Co-MgO.