UV–Visible–Infrared Light Driven Thermocatalysis for Environmental Purification on Ramsdellite MnO₂ Hollow Spheres Considerably Promoted by a Novel Photoactivation

Novel ramsdellite MnO 2 hollow spheres consisting of closely stacked nanosheets (R-MnO 2 -HS) were synthesized by a facile method. The R-MnO 2 -HS sample was characterized with SEM, XRD, TEM, BET, XPS, diffusive reflectance UV–vis–IR absorption, etc. Remarkably, R-MnO 2 -HS exhibits highly efficient catalytic activity for the purification of benzene (a carcinogenic air pollutant) under the full solar spectrum or visible–infrared irradiation, even under the infrared irradiation. Its catalytic activity (initial CO 2 production rate) under the full solar spectrum irradiation is as high as 210.5 times higher than TiO 2 (P25), a well-known benchmark photocatalyst for environmental cleanup. The excellent catalytic activity of R-MnO 2 -HS is ascribed to its efficient thermocatalytic activity and its efficient photothermal conversion in the whole solar spectrum region, resulting in high efficient solar light driven thermocatalysis. Very interestingly, a novel photoactivation, which is completely different from the well-known photoactivation induced by photoexcited electrons and holes on TiO 2, considerably enhances the solar light driven thermocatalysis. By use of CO temperature-programmed reduction (CO-TPR) under solar light irradiation and in the dark together with density function theory (DFT) calculations, the origin of the novel photoactivation was revealed: The lattice oxygen activity plays a crucial role in the thermocatalysis on MnO 2 . The solar light irradiation significantly promotes the lattice oxygen activity of R-MnO 2 -HS, consequently resulting in a considerable enhancement in the thermocatalytic activity.