The Research Of Photocatalvtic Hydrogen Production By The Si Nanowires Array-based Photocatalvtic System

Due to its unique photoelectronic properties, silicon nanowires have attracted more and more attention. With the deepening of the research, the use of silicon nanowires (SiNWs) array as catalysts to the hydrogen production has also attracted widespread interest and become a new hotspot in the field of photocatalytic hydrogen production. For this purpose, in our paper, we design and build a series of photocatalytic system based on the SiNWs by using the ethylenediamine tetraacetic acid metal salt (EDTA-M, M= Ni, Co) as the photosensitization agent and sacrifice agent. The photocatalytic hydrogen production performance of the catalytic system was examined under the irradiation of simulated sunlight. The concrete research contents are as follows:(1) Under the irradiation of simulated sunlight, using the EDTA-Ni as a photosensitive agent and sacrificial agent, the EDTA-Ni sensitizated SiNWs system was built and the photocatalytic hydrogen production performance was also investigated. In addition, the photocatalytic mechanism of the catalytic system was preliminary discussed by using the photoelectric chemical means. The results show that the EDTA-Ni sensitized SiNWs is a more excellent photocatalytic hydrogen production catalysts, the photocatalytic hydrogen production rate can be up to 2.41 L·m2·h-1. In the process of photocatalytic hydrogen production, the EDTA-Ni works as a sensitizer and sacrificial agent which play a very important role to improve the visible light utilization efficiency of SiNWs. When using EDTA-Ni instead of EDTA-Na, the light utilization efficiency (λ> 500 nm) of SiNWs increased twice. In addition, the experimental results also show that the EDTA-Ni sensitied SiNWs has high light stability and cycle performance.(2) Based on the above research, using the EDTA-Ni/EDTA-Co mixed complexes as sensitizer and sacrificial agent instead a single EDTA-Ni, the EDTA-Ni/EDTA-Co mixed complexes co-sensitized SiNWs system was built and the photocatalytic hydrogen production performance was surveyed under the irradiation of simulated sunlight. The research results show that the synergistic effect of EDTA-Ni/EDTA-Co can further improve the photocatalytic hydrogen production efficiency of SiNWs and its photocatalytic hydrogen production rate can be up to 2.8 L·m2·h-1. The photoelectrochemical method also showed that, in the process of photocatalytic hydrogen production, the obvious synergy exists between EDTA-Ni and EDTA-Co, which may be casued by the the energy transfer between them.(3) The TiO2-Si nanoforest was built by the branched TiO2 nanorods on the SiNWs. Then, the photocatalytic hydrogen production performance of the nanoforest was investigated by using EDTA-Ni as a photosensitive agent and sacrificial agent and the photoelectrochemical mechanism of photocatalytic hydrogen production also has been preliminary discussed. The results show that the the photocatalytic hydrogen production performance of TiO2 has been improved by building the TiO2-Si nanoforest composite photocatalytic system. Compared to the P25 simple coating on the SiNWs array, TiO2-Si nanoforest photocatalytic hydrogen production rate is enhanced nearly 2.5 times. This means that building TiO2-Si nanoforest is a good way for TiO2 nanomaterials immobilizated on a solid substrate, which can effectively solve the decline of the photocatalytic efficiency of the immobilized TiO2 nanoparticles.