Controlled Synthesis Of Haloxy-bismuth Based Nanoarrays And Their Photoelectrocatalytic Water Splitting Performance

Hydrogen energy has attracted wide attention due to its high energy density,clean and renewable characteristics.Among many hydrogen production methods,photoelectrocatalytic water splitting for hydrogen production has become one of the most promising methods at present.In recent years,bismuth halide oxide has been considered as a promising photoelectric material because of its unique layered structure,adjustable electronic structure and excellent physical and chemical properties.In view of these advantages of oxy-bismuth halide based semiconductor materials,this paper aims to construct BiOX（X=C l、Br、I）nanoarray structure supported on Cu₂S and iodide doped BiOCl_1-xI_x nanoarray by environmentally friendly chemical reaction.Through heterojunction engineering and halogen element doping,the band gap and interface structure of the material are adjus ted.By optimizing the experimental parameters,the micro-morphology and crystal structure of the material can be adjusted and controlled,so as to promote the separation and transmission of photoelectric charge and improve the performance of photoelectroc atalytic water splitting.The specific work is as follows:First,synthesis and photoelectric properties of photo-activated BiOCl/Cu₂S heterojunction nanoarrays.Cu₂S nanorod arrays（Cu₂S NAs）were synthesized on copper foam（CF）by in-situ oxidation-sulfide two-step method at room temperature.Then,BiOCl ultrathin nanosheets were deposited on the surface of the nanorods by SILAR method,and three-dimensional layered BiOCl/Cu₂S heterojunction nanoarrays were obtained.Finally,the active substance Bican be implanted in situ on the surface of BiOCl nanosheets by photoactivation.The morphology and structure of the nanoarray can be effectively controlled by adjusting the number of deposition cycles and temperature.The experimental results show that the con struction of heterojunction can effectively promote charge separation.At the same time,under the synergistic contribution of SPR effect of active substance Bi,the light absorption range can be effectively broadened,so as to significantly improve the ph otocatalytic activity.The photocurrent of the catalyst can reach 1.24 m A cm^-2 at bias voltage of 0 V_RHE,which is3.3 times higher than that of Cu₂S and 4.2 times higher than that of BiOCl.Second,synthesis and photoelectric properties of core-shell BiOBr@Cu₂S Z-scheme heterojunction nanoarrays.Using the Cu₂S NAs in Chapter 2 as the precursor,a nanoarray structure with Cu₂S as the core and BiOBr nanosheets as the shell was obtained by the SILAR method at room temperature.Among them,the morphology and structure of the core-shell array can be effectively controlled by adjusting the number of deposition turns and temperature.The experimental results confirmed that the design of the core-shell array greatly shortens the charge diffusion length and promotes the charge transfer;and the carrier transfer pathway of the Z-scheme heterojunction can not only accelerate the separation and transfer of photogenerated carriers,but also It can retain the photo-generated electrons and holes with strong redox ability,thereby enhancing the photoelectric catalytic activity.Under the bias voltage of 0 V_RHE,the photocurrent value of the catalyst can reach 1.75 m A cm^-2,which is 4.6 times and 5.3 times higher than that of the single component Cu ₂S and BiOBr,respectively.Third,synthesis and photoelectric properties of iodide doped BiOCl _1-xI_xnanosheet arrays.BiOCl_1-xI_x（x=0.1、0.18、0.24、0.32）nanosheet arrays with oxygen vacancy defects were prepared by Silar method at room temperature.The iodide doping can realize the continuous regulation of the band gap,and the band gap varies in the range of 2.56 e V～1.36 e V.The red shift of the absorption band edge and the narrow band gap are beneficial to improve the photoelectrocatalytic performance driven by visible light.The formation of oxygen vacancies is not only conducive to trapping electrons,but also to enhancing the electrostatic field inside the crystal,thus improving the migration of photogenerated carriers.At the same time,the large specific surface area of the nanosheet array structure is helpful to expose more catalytic active centers.The photocurrent value of the solid solution can reach 1.75m A cm^-2 at bias voltage of 0 V_RHE,which is 3.2 times and 2.2 times higher than that of the single component BiOCl and BiOI,respectively.