Improved photocatalytic performance of acetaldehyde degradation via crystal plane regulation on truncated octahedral CeO₂

In this study, the truncated octahedral CeO₂ (CeO₂-to) with special morphology was prepared by the solvothermal method with oleic acid (OA) and oleamine (OM) as the morphology-directing agents. High-resolution transmission electron microscopy (HRTEM) results show that CeO₂-to exposes composite {100} and {111} facets, while CeO₂ cubic (CeO₂-c) and CeO₂ octahedral (CeO₂-o) only expose single crystal facets of {100} plane and {111} plane, respectively. Interestingly, this CeO₂-to photocatalyst exhibits remarkable photooxidation performance of gaseous acetaldehyde (CH₃CHO) degradation, in which CO₂ generation value reaches 1.78 and 7.97-times greater than that of CeO₂-c and CeO₂-o, respectively. In addition, the active species trapping experiment signifies that superoxide (·O₂⁻) and holes (h⁺) are the main reactive substances during the CH₃CHO degradation process, and the electron paramagnetic resonance (EPR) spectra indicates that the former is the major contributor. Notably, the electron transfer mechanism between CeO₂-to {100} and {111} facets and the surface oxygen adsorption ability are revealed via density functional theory (DFT) calculations. It is also confirmed that {100} facets are more conducive to the absorption of acetaldehyde than {111} facets. Finally, a reasonable mechanism for improved photocatalytic CH₃CHO degradation on CeO₂-to is proposed based on relevant experiments and DFT calculations. This study demonstrates that the systematic development of surface homojunction structured photocatalysts can efficiently increase the degradation activity for volatile organic compounds (VOCs). It also offers additional direction for optimizing the photocatalytic activity of other cerium-based photocatalysts.