A novel thermophotocatalyst of mixed-phase cerium oxide (CeO2/Ce2O3) homocomposite nanostructure: Role of interface and oxygen vacancies

Abstract

A mixed phase metal oxide system is considered as a highly active and stable photocatalyst due to extended absorption spectrum and reduced recombination of the photogenerated carriers as a result of their efficient separation at the phase interface. In ceria such a mixed phase has two different oxidation states wherein the oxygen deficient state has a complementary characteristic of high charge carrier mobility. Further due to the direct dependence of mobility on temperature in such a system, and its synergy with reduced recombination in mixed phase and extended absorption spectrum of solar radiation, it suits a solar concentrator based photo-catalytic reactor which normally works at high temperature. Accordingly a mixed phase (biphasic) homo-composite (same material with different oxidation state) of low temperature engineered cerium oxide (CeO2/Ce2O3) nanostructures was prepared by hydrothermal method. The physico-chemical characterization of the vacuum annealed disordered nanostructure material revealed the presence of biphasic homocomposite with extended absorption spectrum and also the presence of oxygen vacancies at the junction of phases. The mixed phase Ce-oxide with Ce3+/Ce4+ introduced disorder in the surface layers of nanostructure as well. The photoactivity of CeO2 nanoparticles was evaluated using methyl orange as a probe pollutant both under UV and visible irradiation over a wide range of temperature. The photocatalytic activity and its temperature dependence were found to be high compared to monophasic Ce-oxide. This work provides a rational design and development procedure for high-performance thermo-photocatalysts.