Research On Design,preparation And Photocatalytic Performance Of Organic-Inorganic Lead Halide Perovskite Based Photocatalysts

Hydrogen,as a new energy carrier,is considered to be the most potential energy in the future.Solar-light-driven photocatalytic hydrogen evolution is a technology converting solar energy to chemical energy,which can completely solve the energy and environmental pollution problems.Photocatalytic splitting hydrohalic acids(HX),as an excellent technology for hydrogen evolution,has serval advantages comparing with water splitting,such as high theoretical solar-to-hydrogen efficiency,low overpotential,and value-added by-products.The organic-inorganic perovskite materials(represented by MAPbI3)exhibit high extinction coefficient,outstanding ionic mobility and long carrier diffcusion length,well matching to the photocatalyst requirement.However,perovskite materials are extremely unstable in water,limiting their photocatalysis application.In this work,we designed low-cost and easily prepared photocatalysts by halide doping and cocatalyst strategy.In the photocatalytic HX splitting system,new photocatalysts show effective hydrogen evolution and high aqueous stability.Moreover,the micro-reaction process and mechanism were in-depth investigated.The primary study conclusions were summarized briefly as follows:(1)We obtained a hybrid perovskite MAPb(I1-xBrx)3 by one-pot crystallization.MAPb(I1-xBrx)3 can keep stable in the photocatalytic reaction system by tuning the components of aqueous media.MAPb(I1.xBrx)3 is demonstrated to be a superior visible-light-driven photocatalyst for H2 evolution in aqueous HI/HBr solution with no Pt as a cocatalyst.An optimized MAPb(I1-xBrx)3(x=0.10)shows a highest H2 evolution rate of 1471 μmol h-1 g-1 under visible light(X,>420 nm)illumination,which is～40 times higher than that of pure MAPbI3,and the dual-halide perovskite is rather stable showing no obvious decrease in the photocatalytic activity over 60 runs(252 h).The perovskite inherent structural stability is further evidenced by XRD,UV-vis spectra and EDS elemental mapping of MAPb(I1-xBrx)3 measured after cycled photocatalytic reaction.The solar HI splitting efficiency of MAPb(I1-xBrx)3(x=0.10)is determined as 1.42%.The mechanism behind photocatalytic H2 evolution enhancement is elucidated by the experimental and computational methods.(2)Ni3C nanocrystals were prepared by thermal synthesis method,and then successfully loaded onto the surface of MAPbI3 crystal by electrostatic adsorption.In the photocatalytic reaction process,Ni3C nanocrystals can trap electrons to promote the separation of photogenerated electrons and holes.Moreover,Ni3C can also provide many active sites for the photocatalytic reaction.Under an optimized Ni3C/MAPbI3 ratio of 15 wt.%,composite photocatalyst shows the maximum photocatalytic activity 2362 μmol h-1 g-1,which is～55 times higher than that of pure MAPbI3.Ni3C/MAPbI3 is rather stable showing no obvious decrease in the photocatalytic activity over 200 h.The characterization results confirm that Ni3C/MAPbI3 integrates the strong absorption of MAPbI3,with the low charge transfer resistance and effective carrier separation,and hence leading to a better photocatalytic performance.