Reinforced upconversion and charge separation via mid-gap states in WO3 nanosheet with infrared light driven tetracycline degradation

It is of crucial importance to fabricate near-infrared responsive (NIR) catalysts to maximize the utilization of solar energy. And achieving efficient charge separation under near-infrared light was also a great challenge. Herein, the synergy of both improved upconversion and charge separation performances of WO3 was realized by atomic doping of Cu element. The induced mid-gap states can decrease the required excitation energy of photogenerated electrons to improve the upconversion ability, which enhanced the light absorption capacity of WO3 nanosheet. Moreover, the introduced Cu element not only acted as the trapping sites of photogenerated charges, but also led to the charge redistribution of the crystal structure over WO3, which efficiently enhanced the charge separation process. As a result, excellent tetracycline photodegradation performance under NIR light (mineralization degree reaching 92.4%) was realized, where the rate constant of 1 wt% Cu-WO3 (2.92 × 10-3 min−1) reached 14.4 times over that of pristine WO3 (2.02 × 10-4 min−1).