Study On The Preparation And Photocatalytic CO₂ Reduction Property Of Perovskite/Graphdiyne Nanocomposite

In the past century,the over-consumption of fossil fuels has resulted in excessive emission of carbon dioxide（CO₂）,which consequently brings forth a series of environmental problems such as global warming.However,CO₂ can be considered as a cheap,safe and abundant carbon source.If it can be converted into valuable energy fuels,it will not only mitigate the greenhouse effect,but also contribute to the alleviation of the energy crisis.Metal halide perovskite（MHP）nanocrystals,which possess well light-harvesting ability,low-cost manufacturing and suitable energy band structure,can achieve photocatalytic CO₂ reduction and desirable water oxidation simultaneously,exhibiting great potential in the field of practical artificial photosynthesis.However,the ionic nature of MHP nanocrystals severely reduces their stabilities in the reaction systems containing plenty of water.In addition,the lack of effective catalytic sites and inferior charge separation of MHP result in a poor photocatalytic activity in its pristine form.This thesis has carried out the following two aspects of work around these two issues:（1）We in situ coated graphdiyne（GDY）thin layer on the surface of the as-prepared halide perovskite Cs Pb Br₃ nanocrystals based on a facile microwave synthesis method,to prepare a series of Cs Pb Br₃@GDY_X（X=0.1,0.3,0.5）composite nanocrystal materials,and employ them as photocatalysts for CO₂ reduction.Under the protection of GDY,the stability of the photocatalyst based on Cs Pb Br₃ has been significantly improved in the water-containing system.At the same time,GDY can also act as a hole transport layer to promote the transfer of photo-generated holes from Cs Pb Br₃ to GDY,thereby inhibiting electron-hole recombination.Cs Pb Br₃@GDY_0.3 displays the best photocatalytic CO₂-to-CO performance,achieving 10.2μmol g^-1 h^-1,and photocatalytic stability at least 36 hours.（2）GDY,a new type of carbon allotrope,contains abundant sp-hybridized carbons and triangular cavity structures,which can serve as a favorable substrate for deposition of metal species.Rapid photogenerated electron transfer can be achieved by doping cobalt metal sites on the surface of Cs Pb Br₃@GDY_0.3.Benefitting from the increase of active sites and the improvement of photogenerated carrier separation efficiency,the performance of photocatalytic CO₂ reduction has been significantly improved.Without adding traditional sacrificial reductants,the cobalt-doped photocatalyst achieves a high yield of 27.7μmol g^-1 h^-1 for photocatalytic CO₂ conversion to CO based on water as an electron source,which is about 8 times higher than that of pure Cs Pb Br₃ nanocrystals.This work provides an effective strategy for improving the stability and activity of metal halide perovskite nanocrystals and broadens their application in the field of energy conversion.