Exploring the enhancement effects of hetero-metal doping in CeO2 on CO2 photocatalytic reduction performance.

CO 2 photoreduction performance of CeO 2 has been markedly enhanced by Y doping, which is achieved by the introduction of abundant oxygen vacancies and the intermediate regulations on the catalyst. [Display omitted] • Doping in CeO 2 results in promoted CO 2 photoreduction to CO. • Doping in CeO 2 results in differential generation/transformation of intermediates. • CO 2 adsorption/activation facilitates generation/transformation of intermediates. • The intermediates accumulation is the main obstacle to achieve sustainable activity. Doping hetero-metal ions in semiconductors, especially metal oxides, is a common practice to elevate their photocatalytic reduction activity. However, the underlying enhancement mechanism of doping different metal ions into the host lattice on photocatalytic CO 2 reduction has been rarely explored and thus remains unclear. In this work, CeO 2 nanoparticles doped with three different metal ions (Ce M , M = Y, La, Mo) have been synthesized, which exhibited significantly improved photo-reduction CO 2 activity. According to the analysis of Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), Y and Mo doping results in increased oxygen vacancy concentration in CeO 2 , which promotes the absorption of UV–visible light and the separation/transfer of electrons and holes, consequently elevating the catalytic activity. More importantly, through in - situ FT-IR, CO 2 adsorption/activation and the intermediates generated on catalyst surface during CO 2 photoreduction reaction were investigated and discussed in-depth. Similar carbonates and hydrocarbonates, such as HCO 3 −, b-CO 3 2− and m-CO 3 2−, have been found to be produced on CeO 2 and Ce M , while these intermediates accumulated and strongly covered on the catalyst surface have been revealed to be responsible for the gradually declined CO 2 reduction activity and stability. [ABSTRACT FROM AUTHOR]