Study On The Properties Of Photocatalytic CO₂ Reduction Of CsPbBr₃ Based Nanocrystals

Under the pressure of environment deterioration and ever-growing energy demand,the development of clean energy has become one of the core strategic problems that the human beings must face.The new energy technology,represented by sunlight-driven photocatalytic CO₂ conversion,is one of the ideal schemes to realize sustainable development by alleviating energy crisis and environmental pollution.The development of cost-effective photocatalyst systems is a crucial challenge for the extensive application of this technology.In recent years,metal halide perovskite（MHP）nanocrystals have emerged as one of promising photocatalysts in the photocatalytic field,owing to their low-cost,excellent optoelectronic properties and facile processing progresses.However,this kind of nanocrystals generally displays low activity for photocatalytic CO₂ reduction,owing to the lack of intrinsic catalytic sites and the insufficient separation of photogenerated carriers.To improve photocatalytic activity for CO₂ reduction based on MHP material,this thesis carried out two exploratory studies as follows:（1）We have functionalized Cs Pb Br₃ nanocrystals with graphitic carbon nitride containing titanium-oxide species（Ti O-CN）by facile processing progresses,to exploit a series of composite catalysts for photocatalytic CO₂ reduction based on water as an electron source.Microstructure characterization have revealed that Cs Pb Br₃ nanocrystals can be closely anchored on 2D Ti O-CN via N-Br and O-Br bonding.Compared to its congener with pristine Cs Pb Br₃,this employment of Ti O-CN can not only increase the catalytic active sites,but also bring forth an obviously enhanced separation efficiency of photogenerated carriers,leading to obviously enhanced photocatalytic activity for CO₂ reduction to CO.The yield of CO for Cs Pb Br₃/Ti O-CN compiste is over 3-fold and 6-fold higher than those of pristine Cs Pb Br₃ nanocrystals and Ti O-CN nanosheets,respectively,by judiciously modulating the loading amount of Cs Pb Br₃.（2）To solve the dilemma of Cs Pb Br₃surface cation doping,we have demonstrated a doping strategy of anion-exchange-driven cation exchange to prepare a series of cobalt-doped Cs Pb Br₃ nanocrystals（Co_x-Cs Pb Br₃,x=0.01,0.02,0.03,0.04）via simple post treatment with Co（SCN）₂.The partial cation exchange of Pb by Co has a large probability to occur as a concomitant result for opening the rigid halide octahedron structure around Pb during exchange between SCN^-and Br^-.Owing to increased active sites and improved separation efficiency of photogenerated carriers,the cobalt-doped Cs Pb Br₃ nanocrystals exhibit significant improvement of photocatalytic activity for CO₂ reduction.The yield of photocatalytic CO₂ reduction to CO for Co_0.03-Cs Pb Br₃ is over 3-fold than that of pristine Cs Pb Br₃ nanocrystals.The investigation of this thesis will provide some pivotal science clues for further design and development of halide perovskite based photocatalysts.