Synthesis of CdS QDs/NH2-Nb2O5 via electrostatic self-assembly method for highly efficient photocatalytic removal of NO and synchronous inhibition of NO2

The photogenerated electrons and holes induced by CdS QDs under visible light irradiation are beneficial to the generation of ROS (OH and O2–), resulting that the NO being oxidized to NO2– and NO3– over CdS/NH2-Nb2O5 prepared by electrostatic self-assembly mothed. [Display omitted] •A CdS/NH2-Nb2O5 nanocomposite was prepared by two two-step electrostatic self-assembly methods.•Loading CdS QDs on NH2-Nb2O5 can cause a visible light response for the nanocomposite.•CdS/NH2-Nb2O5 exhibited better photocatalytic activity for deep oxidizing NO than NH2-Nb2O5.•CdS QDs lead to the generation of O2– to promote the deep oxidation of NO. A two-step electrostatic self-assembly method was used to first graft –NH2 groups onto the Nb2O5 followed by loading of CdS QDs onto the NH2-Nb2O5 to obtain CdS/NH2-Nb2O5. The performance of the samples under visible light was evaluated under simulated conditions of 25 °C and varying relative humidity (RHs). The results showed that with the increase of RH, the NO removal efficiency by CdS/NH2-Nb2O5 increased first and then decreased, reaching the maximum NO removal efficiency when RH = 50 %. The selectivity of NO2 on CdS/NH2-Nb2O5 (9.01 %) was significantly lower compared to that of Nb2O5 (24.44 %) and NH2-Nb2O5 (19.72 %). The introduction of –NH2 groups and CdS QDs significantly enhanced visible light absorption and improved the separation efficiency of photogenerated charge carriers. In-situ DRIFTS analysis revealed that Cd2+ served as an additional active site for NO adsorption. Furthermore, CdS had a relatively negative conduction band position, which was conducive to the generation of O2–, further inhibiting the generation of NO2. This work provides a new approach to the design and preparation of catalysts for photocatalytic oxidation of NO.