Graphene quantum dots/NiTi layered double hydroxide heterojunction as a highly efficient De-NOx photocatalyst with long persistent post-illumination action

Persistent photocatalysis is an attractive process to broaden the spectrum of environmental applications. Herein, blue luminescent graphene quantum dots (GQD) are incorporated into NiTi-based layered double hydroxide nanosheets (NiTi-LDH) by a facile impregnation method. The enhanced performance of GQD/NiTi-LDH leads to excellent NO photo-removal activity (61 %) and insignificant NO2 release (< 0.6 %), beating the standard TiO2 P25 (48 % and 14.2 %, respectively). Interestingly, after the end of light irradiation period, GQD/NiTi-LDH maintained a NO removal efficiency higher than 20 % for up to 75 min regardless of the previous irradiation time. This De-NOx post-photocatalytic process is the most effective reported at present. The dark/light mechanism is explained by the electron storage capacity of NiTi-LDH under light excitation, which is assisted by the electron migration from GQD to NiTi-LDH. Once the light is shut off, electrons are released and take part in the superoxide radical generation.

Automated summary

In this study, blue luminescent graphene quantum dots (GQD) were incorporated into NiTi-based layered double hydroxide nanosheets (NiTi-LDH) to enhance the photocatalytic removal of NO. After the end of light irradiation period, GQD/NiTi-LDH maintained a high NO removal efficiency, making it the most effective post-photocatalytic NOx removal method reported so far.