Rare-earth single atoms decorated 2D-TiO2 nanosheets for the photodegradation of gaseous O-xylene.

In this work, rare-earth single atoms (La, Er) were decorated on the surface of 2D-TiO2 nanosheets by an impregnation-calcination strategy. The formation of rare-earth single atoms was certified by AC HAADF-STEM and XAS. TiO2 decorated with rare-earth single atoms (La1-TiO2 and Er1-TiO2) exhibited outstanding photocatalytic activity than pure 2D-TiO2 nanosheets (2D-TiO2) towards gas-phase degradation of O-xylene. Compared with 2D-TiO2, the rare-earth single atoms greatly improved the adsorption capacity of O-xylene without increasing their specific surface area. This is because rare-earth single atoms provide additional adsorption sites and reduce the adsorption energy of O-xylene. In addition, the hybrid orbital formed by the combination of rare-earth single atom and oxygen atom is beneficial to the rapid transmission and separation of photo-induced electrons, thereby improving the performance of photocatalytic degradation. In addition, in-situ DRIFTS and GC-MS were used to reveal the photocatalytic oxidation mechanism. Interestingly, the results showed that the La1-TiO2 and Er1-TiO2 samples can reduce the types of intermediates and simplify the reaction route, implying that the single atoms play an important role in the modulation and thorough mineralization of intermediate products. This work shows that the rare-earth single atom decorated 2D-TiO2 nanosheets have great potential in photocatalytic air pollution control.