Selective activation of dioxygen to singlet oxygen over La-Si co-doped TiO2 microspheres for photocatalytic degradation of formaldehyde

Volatile Organic Compounds (VOCs) are highly harmful to human beings and other organisms, and thus the elimination of VOCs is extremely urgent. Here, La-Si co-doped TiO2 microsphere photocatalysts, which were prepared by a hydrothermal method, exhibited high photocatalytic activity in the decomposition of formaldehyde compared with TiO2. The improved activity can be attributed to the promoted separation efficiency and density of the charge carriers, as verified by the electrochemical results in combination with density functional theory calculations. In addition, the Si dopant changed the microstructure and surface acidity, while the addition of La promoted the separation efficiency of charge carriers. More interestingly, it was found that singlet oxygen was the key species in the activation of molecular dioxygen, and it played a pivotal role in the photocatalytic decomposition of formaldehyde. This work provides a novel strategy for the selective activation of dioxygen for use in the decomposition of formaldehyde.