Synergistic integration of thermocatalysis and photocatalysis on black defective (BiO)2CO3 microspheres

Abstract

A novel environmental catalyst, black defective (BiO)₂CO₃ microspheres, was prepared by a vacuum heat treatment method. It was interesting to discover that the as-obtained catalyst contained the Bi element phase, Bi⁵⁺ ions and oxygen defects. These components endowed the black (BiO)₂CO₃ microspheres with efficient catalytic performance in NO removal. In situ DRIFTS investigation demonstrated that the adsorbed NO molecules at the active sites (Bi⁰, Bi⁵⁺ and oxygen defects) could react with the O₂ activated by oxygen defects to produce nitrogen dioxide, nitrite and nitrate in the dark. When visible light was applied, highly enhanced catalytic activity can be achieved. On one hand, the visible light was transformed to thermal energy, accelerating the thermocatalytic reaction. On the other hand, the visible light could directly initiate the photocatalysis reaction as the generated oxygen defects could narrow the band gap of (BiO)₂CO₃ and the plasmonic effect of the Bi element promoted the separation of electron–hole pairs. The highly efficient performance for NO removal under visible irradiation was correlated with the synergistic integration of thermocatalysis and photocatalysis. In addition, a facile method was developed to activate and regenerate the used catalyst for recycling application. This work could provide an innovative technology for NO removal by exploiting the synergistic integration of room temperature catalysis and visible photocatalysis and opens up new opportunities for the design of efficient and low-cost catalysts for air purification.