Raspberry‐Like Microspheres of Core–Shell Cr(2)O(3)@TiO(2) Nanoparticles for CO(2) Photoreduction

To promote the interaction of p–n semiconductors, raspberry‐like microspheres of core–shell Cr(2)O(3)@TiO(2) 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 Cr(2)O(3) 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 TiO(2) in the fourth step, but these monoclinic TiO(2) nanocrystals undergo a phase transition when the applied calcination temperature is above 550 °C. As a result, TiO(2)(B), a magnéli phase of Ti(4)O(7) and Cr(2)Ti(6)O(15) compounds, resulting from inner doping between Cr(2)O(3) and TiO(2), is formed. The close interaction of Cr(2)O(3) and TiO(2) forms a p–n junction that decreases the recombination of photogenerated electron–hole pairs, leading to enhanced production of CH(4) by photocatalytic reduction of CO(2).