Synthesis Of Inorganic Perovskite Quantum Dots And Their Photocatalytic Degradation Of NO Gas

The situation of environmental pollution is becoming increasingly critical with the rapid industrial economic development.Among many air pollutants,acid rain,photochemical smog,PM 2.5,and other substances caused by nitric oxide（NO）seriously threaten human health and survival,so it is urgent to find a fast,effective,and non-toxic method to purify NO.At present,several technologies have been developed to purification NO,among which photocatalytic technology is considered to be one of the most potentials that can solve environmental problems for its high efficiency and environmental protection.In the past five years,inorganic perovskites have continued to attract the attention of scholars from various countries because of its excellent photoelectric performance and stability,and have set off a research boom on semiconductor devices.These two years,inorganic perovskites began to appear in the form of photocatalysts.However,the NO photocatalytic performance and mechanism of inorganic perovskite quantum dots have not been studied,and further improvement of the NO photocatalytic efficiency remains to be solved.In this paper,inorganic perovskite quantum dots are used as photocatalysts to research their catalytic effect on NO under visible light.The research ideas and main conclusions are as follows:（1）Cs Pb Br₃ quantum dots（QDs）were prepared by the hot-injection method,considering that the oleic acid ligands of quantum dots are easy to make them aggregation,lead to the photo-generated carriers are prone to radiative recombination between quantum dots.Therefore,graphene oxide（GO）with unique physicochemical properties is introduced to improve QDs carrier transport performance.To study the change of crystal structure and optical properties of quantum dots with the concentration of GO changing,three kinds of QDs-GO（10 wt%、20 wt%、40 wt%）complexes were prepared.As the GO concentration increases,there is no phase change in the crystal structure of QDs,and the absorption cut-off edge is gradually red-shifted.Besides,the photoluminescence peak intensity is significantly reduced and the lifetime is shortened compared with pure quantum dots,indicating that GO provides a new transmission path for the photo-generated carriers which accelerates the separation of charge between Cs Pb Br₃ QDs and GO and inhibits surface recombination.The QDs-GO complexes exhibit properties that facilitate photocatalytic reactions.（2）The photocatalytic performance of perovskite is closely related to the optical absorption coefficient,the rate of charge separation,and recombination.To study the photocatalytic performance of Cs Pb Br₃ QDs and the composites,it was used to test NO degradation efficiency under visible light as a photocatalyst.The results show that the photocatalytic efficiency of Cs Pb Br₃ QDs is 58.8%,and the QDs-GO composite exhibits higher photocatalytic efficiency.Among them,40 wt%QDs-GO show the best photocatalytic performance,and efficiency reaches 99%.Besides,the stability of 40 wt%QDs-GO was evaluated by four continuous recycling tests,the final efficiency still maintained at 91%.This work provides new ideas for the application of Cs Pb Br₃ QDs in the catalytic field.（3）Taking into account the unfriendly environment of the Pb element in Cs Pb Br₃ and the poor thermal stability of the material itself,a lead-free Cs₂Ag Bi Br₆ nanocrystal（NCs）was synthesized by hot injection method.The test results show that the prepared Cs₂Ag Bi Br₆ NCs have uniform size,good dispersion,and good response to visible light.To exclude the effect of organic ligands on the performance when photocatalytic reaction,the necessary washing of the nanocrystals was proposed,and the washing only affected the size of the crystal slightly.After 30minutes of visible light irradiation,the catalytic efficiency of washed Cs₂Ag Bi Br₆ NCs reaches97.22%.After four continuous recycling tests,the efficiency remains stable.This work helps to advance the progress of inorganic lead-free perovskites in the field of NO photocatalysis and pave the way for the development of green and stable photocatalysts.