Highly efficient UV-visible-infrared photothermocatalytic removal of ethyl acetate over a nanocomposite of CeO2 and Ce-doped manganese oxide

A unique nanocomposite of CeO2 nanoparticles and Ce-doped manganese oxide nanofibers having a crystalline cryptomelane-type octahedral molecular sieve (KMn8O16·nH2O, abbreviated as OMS-2) structure (denoted CeO2-CeOMS-2) was prepared by the reaction of Ce(NO3)3 and KMnO4 at 90 °C. CeO2-CeOMS-2 shows extremely high photothermocatalytic activity, very low selectivity for acetaldehyde (an unfavorable byproduct), and excellent durability for ethyl acetate removal under UV-visible-infrared (UV-vis-IR) irradiation. In striking contrast, pure CeO2, pure OMS-2, and TiO2 (P25) showed much lower photothermocatalytic activities and higher selectivities for acetaldehyde. The CO2 production rate within the first five minutes (rCO2) of reaction with CeO2-CeOMS-2 was as high as 1102.5 μmol g–1 min–1, which is 137, 17, and 30-times higher than those of pure CeO2, pure OMS-2, and TiO2 (P25), respectively. CeO2-CeOMS-2 also shows good photothermocatalytic activity under vis-IR (λ > 420 or 560 nm) irradiation. Further, even under vis-IR (λ > 830 nm) irradiation, efficient photothermocatalytic activity was achieved. In addition, the catalytic activity of CeO2-CeOMS-2 is far superior to those of pure CeO2 and OMS-2, which is attributed to the fact that Ce doping significantly improves the lattice oxygen activity of OMS-2. The high photothermocatalytic activity of CeO2-CeOMS-2 arises from the synergy between the photocatalytic effect of the CeO2 nanoparticles and light-driven thermocatalysis of the Ce-doped OMS-2. The novel photoactivation of Ce-doped OMS-2, which is unlike that of conventional photocatalysis on semiconductor photocatalysts, further promotes the catalytic activity because the surface oxygen activity of Ce-doped OMS-2 is promoted upon UV-vis-IR or vis-IR (λ > 560 nm) irradiation.