A new mechanism for visible light photocatalysis: generation of intraband by adsorbed organic compounds with wide-bandgap semiconductors

Abstract

Wide-bandgap semiconductors are generally effective for the photocatalytic degradation of VOCs under UV light irradiation. However, we found that various VOCs could be effectively degraded and even mineralized by a variety of wide-bandgap semiconductors under visible light irradiation. The findings of our study indicate that adsorption of VOCs on catalysts generated a narrow bandgap between the ground state of the adsorbed VOCs and the conduction band of the catalysts. Such a bandgap induced visible light absorption, generating photoelectrons that are subsequently transferred from the VOCs to the conduction band of the catalyst. The photoelectrons are then captured by the surrounding oxygen, producing reactive superoxide radicals to attack the VOCs, leading to their degradation and mineralization. The degradation efficiency of VOCs by semiconductors under visible light is greatly dependent on the types of semiconductors and VOCs. This study uncovers a new mechanism for wide-bandgap semiconductor photocatalytic degradation of VOCs in visible light irradiation.