Raspberry-Like Microspheres of Core-Shell Cr2O3@TiO2 Nanoparticles for CO2 Photoreduction

To promote the interaction of p-n semiconductors, raspberry-like microspheres of core-shell Cr2O3@TiO2 nanoparticles have been fabricated through a five-step process. Raman spectroscopy of products calcined at various temperatures reveal that the titania shell causes crystal distortion of the Cr2O3 core, without changing the microstructures of the fabricated core-shell microspheres. In situ and time-resolved synchrotron-based powder XRD reveals the formation of monoclinic TiO2 in the fourth step, but these monoclinic TiO2 nanocrystals undergo a phase transition when the applied calcination temperature is above 550 degrees C. As a result, TiO2(B), a magneli phase of Ti4O7 and Cr2Ti6O15 compounds, resulting from inner doping between Cr2O3 and TiO2, is formed. The close interaction of Cr2O3 and TiO2 forms a p-n junction that decreases the recombination of photogenerated electron-hole pairs, leading to enhanced production of CH4 by photocatalytic reduction of CO2.