Study On Co-catalytic Properties Of Nickel-cobalt Phosphide And Boron Nitride In Photocatalytic Reaction

The greenhouse effect and energy crisis have become the major problems needed to be solved urgently nowadays.Direct conversion of solar energy into chemical energy by photocatalysis can effectively solve energy and environment problems,such as photocatalytic H₂production,photocatalytic CO₂reduction,and so on.Cadmium sulfide has been widely studied for its excellent visible light response and suitable band gap.However,the photocatalytic activity and stability of CdS are limited due to the high recombination rate of photogenerated electron-hole pairs and the photocorrosion.It is effective to modify CdS by various methods in order to change the photocatalytic activity of CdS,including ion doping,composite with other semiconductors,morphology control,etc.In this thesis,the co-catalytic performance of NiCo₂P for CdS was explored in photocatalytic CO₂reduction reaction and the structure matching through morphological regulation was optimized;On this basis,NiCo₂P/CdS was further composited with BN and the effect on the photocatalytic performance was investigated.The main contents are given as follows:（1）Different cobalt-based bimetallic phosphates MCo₂P（M=Fe,Ni,Cu,Zn）were synthesized and the effects on the catalytic performance of CdS were discussed.In the photocatalytic CO₂reduction,the hydrogen evolution performances of different composite catalysts were improved,and NiCo₂P as a cocatalyst showed the highest ability of promoting the CO₂reduction.The production rates of CO,CH₄and H₂were 90.10μmol·g^-1·h^-1,40.53μmol·g^-1·h^-1and 2391.33μmol·g^-1·h^-1,respectively.（2）Different morphologies of NiCo₂P and CdS were prepared and used for the formation of NiCo₂P/CdS composite catalysts with different structure.The results of photocatalytic CO₂reduction reaction showed that 1D/0D NiCo₂P/CdS had the best photocatalytic performance.Compared with NiCo₂P nanoparticles,NiCo₂P nanorods have better co-catalytic performance and the generation rate of CO₂reduction products is improved obviously.The four composites also showed excellent performance in the photocatalytic H₂production from water.1D/0D NiCo₂P/CdS had the best hydrogen evolution rate of 148.05 mmol·g^-1·h^-1,which was 45.14 times that of pure CdS(3.28mmol·g^-1·h^-1).The matching structure of 0D CdS and 1D NiCo₂P had better photoelectric performance.（3）Different morphologies of BN were composited with NiCo₂P/CdS to form ternary composites.The performance of photocatalytic CO₂reduction in water-triethanolamine system was compared.The addition of BN nanosheets,BN nanoparticles and commercial BN would reduced the CO₂reduction product and increase the hydrogen evolution rate.Compared with BN nanoparticles,the composite catalyst with BN nanosheets showed the highest hydrogen evolution rate in photocatalytic CO₂reduction,which was 3702.44μmol·g^-1·h^-1.（4）The effecting factors on the performance of BN/NiCo₂P/CdS in photocatalytic hydrogen evolution from water were discussed.With triethanolamine as sacrificial agent,the introduction of BN improved the hydrogen evolution rate significantly.Considering that the ultraviolet-light responded BN,the catalyst system had the best hydrogen evolution rate under the irradiation of UV-Vis.10 wt%BNNS/NCP/CdS composite showed the highest photocatalytic hydrogen evolution rate:15.75 mmol·g^-1·h^-1,which was30.9 times that of pure CdS(0.51 mmol·g^-1·h^-1).