Preparation Of Si Nanowire Array Composite Films And Their Photoelectrochemical Properties

Ordered nanoarray films have wide application prospects in photoelectrodes for efficient water decomposition due to their large specific surface area for light absorption and ideal charge transfer process.In this paper,metal oxide material is introduced to modify the internal structure of the photoelectrode,so as to achieve the electronic transmission speed of the photomaterial in the process of photohydrolysis hydrogen production,increase the specific surface area,enhance the ability of the photoelectrode to capture the sunlight,and inhibit the effects of the composite electron holes in the photoelectrode.At the same time,the mechanism of internal electron transition and transfer is studied in detail.It provides new ideas and foams for improving the performance of photohydrolysis hydrogen production.The main work content is as follows:（1）Heterojunction formed by Si NWs photoelectrode coated with TiO₂ modified by Fe₂O₃ nanometer prickles is used to realize effective separation of hole electron pairs and improve the efficiency of photohydrolysis hydrogen production.A 3D photoanode of Fe₂O₃/TiO₂/Si was prepared by metal-assisted chemical etching,spray pyrolysis and hydrothermal synthesis.The reaction temperature is constant,the hydrothermal reaction time is changed,and the changes of their performance and morphology in the photoelectric chemistry（PEC）are observed.Moreover,the photoelectrode was characterized in detail.The photocurrent density of Fe₂O₃/TiO₂/Si layered photoelectrode showed 3.8 mA/cm^-2 at the bias pressure of 1.23v（vs.RHE）,which was 87.5 times higher than that of Si nanowires array photoelectrode.The electron transport in photoelectrode is also analyzed.The improvement of PEC performance can be attributed to the synergistic effect of large surface area,lower charge transfer resistance and higher charge separation capability in the layered structure.（2）Research on the application of WO₃ and Si NWs collaborative interface in the field of efficient photohydrolysis hydrogen production.WO₃ seed layer was prepared by dipping and pulling method with silicon material as the substrate directly,which can not only protect Si NWs,but also provide a growth template for the formation of 3D structure of optical electrode.3D WO₃/Si photoanode was prepared by hydrothermal composite WO₃nanowires on its surface,and the photoelectric chemical properties of the photoelectrode were tested and analyzed.At a bias of 1.23v（vs.RHE）,the photocurrent density of 1.8mA/cm^-2 is approximately 30 times that of Si NWs.The improved PEC water decomposition performance of WO₃/Si photoanode can be attributed to the accelerated separation and transmission of photoelectric hole pairs,thus increasing the photocurrent density.It provides an effective method for studying the photochemical properties of photocatalyst to inhibit photoelectron hole recombination and to increase the photoelectrode ratio surface.The reliability of improved PEC performance by 3D structured light electrode is further verified.