| With the increasing emphasis on clean energy and renewable energy, photocatalytic splitting water into hydrogen has been receiving extensive interest. As a good candidate of semiconductor photocatalytic materials, Ti O2 has many advantages, such as strong oxidation and reduction activity, stability, cheap and easy accessibility. Nano-Ti O2 is widely applied to the photocatalytic water splitting, photocatalytic pollutants degradation, air purification, sterilization, etc. But the high recombination rate of photo-induced carrier and small specific surface area result in the low photocatalytic ativity of pure Ti O2. How to improve Ti O2 photocatalytic performance by modification is still a challenging and meaningful topic Scientists discover that some new defects will form on the surface of catalyst after loading different co-catalyst. These defects can capture photo-induced carrier and prolong their life, therefore photocatalytic activity is improved. Furthermore, some morphology of Ti O2, such as nanowires, nanorods, nanotubes, etc, can enhance the hydrogen production activity benefit from the large surface area. In this dissertation work, Ni S/Ti O2 and Ni S/Ti O2 nanotubes(TNTs) were synthesized by solvothermal method. Hydrogen production activity, influencing factors on photocatalytic action and reaction mechanism were investigated. The main contents and conclusions were as follows:1. Ni S/Ti O2 were synthesized by glycol solvothermal method using P25, nickel nitrate, thiourea as precursors. The photocatalysts were characterized by XRD, TEM, UV-vis and PL. The catalyst’s composition, morphology and the optical response characteristics were analyzed and the effect on the photocatalytic activity with the different amount of Ni S and catalyst were further investigated. The results show that the Ti O2 loaded with 5 wt% Ni S exhibited the highest photocatalytic activity for hydrogen generation under 100 m L of reactive solution(25 vol% methanol water solution) containing 0.05 g of photocatalyst. The largest quantity of evolved hydrogen was ca. 3090 μmol·h-1·g-1 catalyst, almost 96 times as much as hydrogen yield of pure Ti O2. This high activity is attributed to the strong synergistic function of Ni S/Ti O2: 1) The reduction potential of Ni2+/Ni(-0.23 e V) is lower than conduction band of Ti O2(-0.26 e V), which promote the electron transfer from Ti O2 to Ni S; 2) Part of Ni2+ were reduced to Ni atoms. The Ni/Ti O2 contact interface forms a Schottky type barrier, which accelerate the transmission of charge carrier and refrain their recombination.2. TNTs were prepared by hydrothermal method using P25 as starting materials in the high concentration(10 M) Na OH environment. Ni S/TNTs were also synthesized by glycol solvothermal method. The photocatalysts were characterized by XRD, TEM, UV-vis, BET and PL. The catalyst’s composition, morphology and performance were analyzed and the effect on the photocatalytic activity with the different amount of Ni S and catalyst were further investigated. The results showed that TNTs has a one-dimensional tubular structure with diameters of 10-15 nm and it’s specific surface area is 313.79 m2·g-1, which is about 6 times as big as P25’s specific surface area. Compared pure TNTs, the TNTs loaded with 8 wt% Ni S exhibited the largest yield of hydrogen(ca. 7486 μmol·h-1·g-1 catalyst). This high activity can be ascribed to large specific surface area and unique one-dimensional tubular structure of TNTs, which contribute to the highly dispersed active center(Ni S) and rapid electron transfer, respectively. |
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