Hollow macroporous CeO2/β-Bi2O3 heterostructure sphere via one-step spray solution combustion synthesis for efficient photocatalysis

The spherical CeO2/β-Bi2O3 heterostructure with the hollow macroporous structure was synthesized by a simple one-step spray solution combustion synthesis (SSCS). The microstructure, phase composition and optical characteristics of the synthesized samples were investigated by HRTEM, FESEM, BET, XPS, DRS and other characterization methods. The results demonstrate that the prepared samples had a particle diameter of about 1–5 µm and the grain size of around 5.4 nm. The photocatalytic activity of the spherical CeO2/β-Bi2O3 was investigated by visible light degradation of RhB (97.22% in 120 min). Additionally, the heterojunction had a broader visible light absorption in the 400–700 nm range, a substantial red-shift in the absorption edge, and a smaller band gap of 2.54 eV compared to pure CeO2 or β-Bi2O3 materials made using the traditional SCS approach. The spherical shape and large specific surface area (54.625 m2·g−1) of the synthesized heterojunction allow for better coupling of CeO2 with β-Bi2O3, which further reduces the luminescence intensity, enhances light collection and charge transfer, and exposes more surface defects to achieve improved photocatalytic performance. Calculations using density functional theory (DFT) demonstrate that the heterojunction can speed up interfacial charge transfer and reduce the recombination of photogenerated charges, causing the reactants to undergo deep oxidation.