Effect of the phase structure on the catalytic activity of MoO3 and potential application for indoor clearance

Abstract

In this work, α-MoO₃ and h-MoO₃ are synthesized by a simple hydrothermal method. Under ambient conditions, α-MoO₃ has a high catalytic wet air oxidation (CWAO) activity for methylene blue (MB), while h-MoO₃ has no activity: 64% of MB can be degraded after 20 min. When adding an additional man-made light source, the performances of h-MoO₃ and α-MoO₃ remain almost unchanged. However, with elevating the reaction temperature from 25 to 40 °C, the activity has not been improved for h-MoO₃, while the activity of α-MoO₃ also has no improvement from 25 to 35 °C. When the temperature rises to 40 °C, the performance of α-MoO₃ improved significantly: the degradation percentage reaches 90% after 20 min. Crystal structure analysis results show that the activity of α-MoO₃ originates from Jahn–Teller distortion of the [MoO₆] octahedron, resulting in the formation of Lewis acid sites. Furthermore, H₂-temperature programmed reduction (H₂-TPR) and O₂-temperature programmed desorption (O₂-TPD) results indicate that α-MoO₃ has a higher lattice oxygen mobility and a higher oxidization ability than h-MoO₃. This ambient CWAO process is energy-saving and low-cost, which is promising for indoor clearance.