Design And Preparation Of Organic-inorganic Perovskite-based Composite Photocatalysts And Their Hydrogen Evolution Performance

Photocatalytic hydrogen(H2)production based on semiconductor photocatalysts which can converse solar to H2,has become a clean and sustainable solar utilization technology.Recently,hybrid organic-inorganic perovskites such as MAPbI3 have attracted considerable attention in photocatalytic HI splitting due to its excellent photoelectric properties including suitable band gap,high optical absorption coefficient,and outstanding carrier mobility.However,their serious recombination of photogenerated charges at the nanoscale domain hinders the photocatalytic HER rate.Herein,we fabricated two types of stable high-efficiency MAPbI3-based composite photocatalysts by coupling two-dimensional(2D)cocatalysts(black phosphorus and MXene)onto MAPbI3 and implemented for visible-light-driven photocatalytic H2 evolution from HI splitting.Furthermore,we carried out a series of optical/optoelectrochemical measurements to explore their microstructure and photocatalytic mechanism.The specific research results are as follows:(1)Few layer black phosphorus(BP)nanoflakes were prepared by using solvent exfoliation,and coupled with MAPbI3 crystal via electrostatic adsorption to obtained the BP/MAPbI3 composite for photocatalytic H2 evolution from HI splitting.The fabricated 1.2%BP/MAPbI3 can effectively split HI into H2 under visible light irradiation(λ≥420 nm)with an ultrahigh photocatalytic HER rate of 3742 μmol h-1 g-1,which is far higher than that of MAPbI3(35 μmol h-1 g-1).In addition,BP/MAPbI3 shows excellent photocatalytic stability during a 200 h-cycling test of photocatalytic H2 evolution.Finally,we measured a series of optical/optoelectrochemical characterizations,and found that BP can act as an electron promoter to trap electrons derived from MAPbI3 through a type I heterojunction in their interface and leading to excellent photocatalytic H2 evolution performance.(2)Ti3C2 MXene nanosheets were synthesized via HF etching and subsequent exfoliation processes,and then in situ anchored on MAPbI3 for visible-light-driven photocatalytic H2 evolution in HI aqueous solution.We find that the fabricated 4%MXene/MAPbI3 photocatalyst exhibits a boosted photocatalytic HER rate of 3124 μmol h-1 g-1,which is about 89 times higher than that of pure MAPbI3(35 μmol h-1 g-1).Furthermore,the MXene/MAPbI3 shows a long-term stability in MAPbI3-saturated HI solution during the whole photocatalytic reaction.Finally,the study on the microstructure and photocatalytic mechanism of the MXene/MAPbI3 composite photocatalyst reveal that the photogenerated carriers in MAPbI3 can be efficiently separated and transferred to the MXene sites for enhanced H+reduction.Beneficial from a suitable band structure,excellent photoelectric response ability,and electron transport ability,the fabricated MXene/MAPbI3 composite photocatalyst exhibits excellent photocatalytic H2 evolution performance.