The Photoeletrochemical Properties And Mechanism Of Nano SrTiO₃ And SrFeO_3-? Materials In Water-Splitting

With the depletion of fossil energy, the research on new generation of alternative energy is imminent. With more than 60% conversion, fuel cells are the world's main concern. But the high cost of its raw materials, hydrogen restricts the utilization of fuel cells. Photocatalytic water-splitting is the most ideal method of hydrogen production. The construction of photocatalytic system, the selection and synthesis of high performance catalytic materials, and test of photocatalytic properties became the focus of research.In this paper, catalytic Sr Ti O3 and Sr Fe O3-? were prepared by high-energy ball milling. XRD and TEM morphology analysis showed that perovskite-type materials with the grain size around 20 nm were successfully fabricated. The corresponding photoelectrode of Synthetic Sr Fe O3-?, Sr Ti O3, commercial Ti O2 and Sr Ti O3 were prepared through thick film technology. The photoeletrochemical test system was designed and constructed. Materials' band structure, photocatalytic properties and mechanism were tested and analysed. Under 40 W LED white light irradiation, Sr Fe O3-? gained the optimal hydrogen production efficiency, 9.39%, which is much higher than efficiency 3% on conventional Ti O2 with 300~500W xenon lamp(simulated sunlight) irradiation. The experimental results are as follows:1. The results of Mott-Schottky test of each sample under dark and illumination circumstance indicated that Sr Fe O3-? is p-type semiconductor, with the minimum flatband potential(vs. SCE) of 0.81V(dark) and 0.68V(illumination).2. Cyclic voltammetry(CV) test determined each materials redox potential while splitting water. The oxidation potential(oxygen evolution potential) of Sr Fe O3-? was 0.6V vs. SCE, which is the minimum.3. The test of each materials' photocatalytic water-splitting properties was conducted. With 0.78 V bias voltage under 40 W LED white light irradiation, the system using Sr Fe O3-? gained the optimal hydrogen production rate, 2.72×10-3m L/h.4. EIS experiment under dark and illumination circumstance was conducted on the system using Sr Fe O3-? which had the optimal photocatalytic hydrogen production properties. A model of band structure change as well as mechanism of photocatalytic hydrogen production was properly established and interpreted.5. From the photocurrent-time(i-t) curve, for the optimal system using Sr Fe O3-?, the external quantum efficiency of photon-generated carriers was calculated to be 26.85%. Hydrogen production efficiency relative to photon-generated carriers was 34.97%. And hydrogen production efficiency relative to light source was 9.39%.