The Structure Design Of Ni-Based Cocatalyst And Its Influence On CdS For Photocatalytic Water Splitting Reaction Under Visble Light

In recent years, photocatalytic water splitting reaction has caused extensive study. Cadmium sulfide(CdS) is a commonly used attractive visible-light-driven photocatalyst, but the fast photo-generated electron- hole recombination rate and light corrosion limits its application in photocatalysis. One of the simple and effective methods to improve the efficiency of photocatalytic of CdS is the loading of noble metal as co-catalyst on its surface, but the expensive price of the precious metal limits its application. Our study found that inexpensive Ni also has a role in promoting the performance of CdS. Therefore, this paper mainly studied the structure design of Ni-based cocatalysts and its influence on hydrogen production activity of CdS in the photocatalytic water splitting reaction.1. The influence of Ni Nano-film on hydrogen production activity of CdS nanorod in the photocatalytic water splitting reaction.The morphology of the prepared Ni nanoparticles is specific by controlling reducing conditions,using chemical reduction,sodium borohydride reduction system. TEM characterization of Ni particles demonstrates its part of film-like morphology, which is beneficial to its loading on the surface of CdS. Powder X-ray diffractometer(XRD), HRTEM(TEM), X-ray spectroscopy(EDX), fluorescence spectroscopy(PL) and other characterization results of Ni/Cd S photocatalyst show that Ni nanoparticles loading on surface of CdS nanorod is uniformly distributed and the load of Ni has a certain influence on each plane diffraction peak intensity and fluorescence intensity of CdS,which shows that the deposition of Ni nano-film on the surface of Cd S nanorod isselective, the loading cause the fluorescence peak corresponding the intrinsic excitation of CdS nanorod weakened and lifetime of the photogenerated carrier extended. The hydrogen production activity of Ni/CdS with different loading of Ni in the visible photocatalytic water splitting reaction shows that the best hydrogen production activity of Ni/CdS is 40.18 mmol/h/g when the loading of Ni is 1.2 wt%, which has been significantly improved compared to Pt/Cd S(26.8 mmol/h/g,loading amount of 1.25 wt%, the highest hydrogen production rate under the same reaction system), the main reason for this efficient hydrogen production rate is that the formation of nano-Ni film makes its loading on CdS surface more uniform, forms more active sites, inhibits the photo electron-hole complex of CdS, thus increasing the hydrogen production activity.2. The influence of different structures of PtNi bimetallic nanoparticles on hydrogen production activity of CdS in the photocatalytic water splitting reaction.1) The influence of PtNi alloy nanoparticles on hydrogen production activity of Cd S in the photocatalytic water splitting reaction.PtNi alloy nanoparticles are prepared by chemical successive reduction, TEM characterization shows that the size of PtNi alloy nanoparticle is about 5 nm without significant agglomeration occurs. X-ray diffractometer(XRD), HRTEM(TEM), X-ray spectroscopy(EDX),fluorescence spectroscopy(PL) characterization results for PtNi/CdS photocatalysts show that PtNi nanoparticles have a good loading on CdS surface and this loading has a certain influence on each plane diffraction peak intensity of CdS, illustrate the deposition has directivity.Thus the fluorescence intensity of PtNi/CdS appears contrast when compared with the single metal Pt/CdS,demonstrate the alloy formed by two elements appears resonance structure. Ni/CdS. By changing the amount of precursor H2PtCl6, NiCl2 to prepare the alloy nanoparticles PtNi of different massratio and apply in photocatalysis experiments,the results show that PtNi/Cd S hydrogen production rate reaches to the highest 53.4 mmol/h/g when PtNi ratio is 5:5, the reason of the significantly improved hydrogen production activity of PtNi/CdS compared to Pt/CdS(20.1 mmol/h/g), Ni/CdS(34.82 mmol/h/g) is mainly due to the synergistic effect of bimetallic which can enhance electron transfer rate and further reduce photogenerated electron- hole recombination rate.2) The influence of PtNi hollow nanoparticles on hydrogen production activity of CdS in the photocatalytic water splitting reaction.PtNi hollow structure nanospheres with different molar ratios were prepared by chemical successive reduction,using sodium borohydride as a reducing agent and changing the amount of the precursor K2PtCl6 and NiCl2.Transmission electron microscopy(TEM) results show that the size of PtNi hollow nanoparticle is about 50 nm, the thickness of the edge shell is about 2-3 nm,and the particle is not uniform. PtNi/CdS photocatalyst is formed by depositing PtNi hollow nanoparticles on the CdS surface using combined method of chemical deposition and light deposition, and photocatalytic water splitting reaction is carried out with the existence of sacrificial agent, the results show that, PtNi hollow nanoparticles have a certain role in promoting on the photocatalytic properties of CdS, the preferably hydrogen production activity is 29.76mmol/h/g when PtNi molar ratio is 1:0.5. fluorescence test data of PtNi/CdS show. The loading of PtNi hollow microspheres on CdS nanorod surface causes its intrinsic excitation weakened, which is the basic electronics for the enhanced visible hydrogen production activity.