Study On Photocatalytic H₂ Evolution Activity And Photoinduced Charges Properties Of Optimized SrTiO₃ Photocatalysts

In recent years, with the rapid development of industrial technology, exploitation and destruction of nature is becoming more and more serious. The increasing consumption of fossil fuels has resulted in environmental pollution. It is urgent to develop hydrogen energy for protecting the environment so as to prolong the life of nature. The nano-strontium titanate materials because of its good properties such as stable and environment-friendly have aroused great interests. It has been a very good choice of photocatalyst for water splitting, but nano-strontium titanate materials is not perfect. The application of light is limited in the UV, so the utilization ratio of visible light is very low. When the nano-strontium titanate is irradiated with light,there is not enough electrons on the surface of the material. According to previous reports, the surface modification and ion doping can improve the performance of hydrogen evolution, so the goal of this paper is looking for a suitable method and co-catalyst to improve photocatalytic activity of nano-strontium titanate. Specific content are as follows:1. Nano-strontium titanate photocatalysts was synthesized by PC method. X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy measurement methods were used to gain the crystalline phase and morphology of nano-strontium titanate photocatalyst and their photoinduced charge properties. The results show that we really prepared the nanostrontium titanate by a series of experimental operation. Then we use the similar path prepared the Ni²⁺ doped strontium titanate, and the doped samples were characterized by a series of means. Photocatalytic activity results show that the hydrogen production rate of doped strontium titanate was not significantly improved. The surface photovoltage（SPV） results show that the photoinduced charge separation efficiency of doped material has been improved. The transient photovoltage（TPV） results show that Ni²⁺ doping can prolong the lifetime of photogenerated charges, but the photocatalytic hydrogen evolution rate of doped materials has not been significantly improved, which indicated that Ni²⁺ ions just improve the separation of photoinduced charge in the bulk phase, and cannot promote the photocatalytic reaction on the material surface.2. We successfully modified nickel hydroxide onto the surface of nano-strontium titanate, and the hydrogen production rate was increased. The highest rate reached 60 times of pure strontium titanate. To estimate the photoinduced charge behavior of the samples, we test each sample by SPV and TPV. According to the SPV results, we found that the presence of nickel hydroxide can effectively improve the separation efficiency of photogenerated electrons and holes. The TPV results reflect the recombination of the photogenerated electron hole pairs was inhibited and the lifetime of photo carriers was prolong, more electron transfer to the surface of nano-strontium titanate. Nano-strontium titanate modified nickel hydroxide get higher photocatalytic activity for hydrogen evolution.3. We use precipitation method modified cobalt hydroxide on nano-strontium titanate materials surface, but the material showed low hydrogen evolution activity. According to the SPV and TPV test results, modification of cobalt hydroxide did not improve the light induced charge separation efficiency, so nano-strontium titanate with cobalt hydroxide modified get unapparent improved of photocatalytic activity for hydrogen evolution.