Modification And Photocatalytic Properties Of Metal Halide Perovskite MAPbBr₃

Organic-inorganic hybrid perovskites have attracted great attention because of their excellent electrical and optical properties.Owing to a wide band gap,high absorption coefficient,low defect concentration,and micron-scale diffusion length,it is very suitable for pervoskites in the field of photocatalysis,but the sensitivity of pervoskites to air humidity limits its application.As we all know,an excellent photocatalyst needs to possess both good photocatalytic activity and cycle stability.In this project,hybrid perovskite MAPbX3(X=Br,I)material was selected as the research object,and ethanolamine and organic carbon spheres with rich amino(-NH2)and hydroxyl(-OH)groups were used to modify the material in order to improve their stability and photocatalytic activity of the material.The hybrid perovskite MAPbX3(X=Br,I)was synthesized by solvothermal method,and the optimal reaction conditions of the two materials were verified by SEM,XRD,FTIR,Uv-vis,PL test results.The optimal synthesis temperature as well as the morphology evolution process,band gap value and luminescence properties were investigated.The semiconductor semiconductor type,flat band potential and carrier concentration structure information were obtained through electrochemical testing methods including cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and Mott-Schottky(MS).The valence band and conduction band could be calculated based on the flat band potential and band gap.In addition,within the same degradation time,the MAPbBr3 sample also showed better photocatalytic degradation of malachite green organic dyes than MAPbI3,which was attributed to the higher carrier concentration of MAPbBr3,the good photogenerated carrier separation efficiency and higher environmental stability than that of MAPbBr3.Enthanolamine(EA)was introduced into the three-dimensional(3D)MAPbBr3 crystal structure,which replaces the methylamine group to improve its air humidity stability.By the water accelerating decomposition electrochemical test experiment,MAPbBr3 changed into white color and decomposed immediately within 2 seconds of contact with moisture,while ethanolamine perovskite still maintains structural stability within 5 minutes showing better water stability.It is reasonable that amino groups(-NH2)and hydroxylamine(-OH)group of ethanolamine forms a surface hydrophobic layer,which can effectively repel water molecules,improving the environmental stability of perovskite.In addition,the photocatalytic degradation experiments showed that ethanolamine perovskite has a certain decrease compared to that of MAPbBr3 which is assigned to the slow charge transfer along the c-axis inhabited by the insulating organic cation layer.In a word,ethanolamine perovskite has better water stability but weak photocatalytic activity.Organic carbon spheres(CS)with abundant hydroxyl groups on the surface were synthesized by hydrothermal method,and MAPbBr3/C Sx with different mass percentages of CS(X=0%,9%,17%,25%,50%)were successfully prepared by mechanochemical grinding method.Furthermore,SEM,XRD,FTIR,Uv-vis and PL test were used to verify that MAPbBr3/CSx has Pb-O-C chemical bonds between MAPbBr3 and CS,which effectively induced the photogenerated electron-hole separation and improve the photocatalytic performance of the material.The kinetic rate constant of MAPbBr3/CSx(0.03 min-1)is 15 times higher than that of MAPbBr3(0.002 min-1).The cyclic stability test shows that the compound has better 5 cycle stability.The PL,CV and Mott-Schottky electrochemical tests were performed to reveal carrier lifetime and transmission kinetics behavior.The introduction of 17%carbon spheres can significantly improve the electron transport efficiency of the composite(ket=4.6×107 s-1).The photocatalytic efficiency compared to MAPbBr3 is increased by 2 times.