| Nowadays, the fossil fuel resources were non-renewable and it was easy to produce pollutants during using the fossil fuel resources, which had led to the increasingly severe energy crisis and environmental degradation. These have become two big global problems which were to be faced and be solved urgently. While the solar energy resources are huge and do not produce any pollution to the environment including greenhouse effect, which are ideal renewable and clean energy. How to convert the solar energy into usable energy? Semiconductor photocatalytic technology has been recognized worldwide as an ideal way to solve the environmental pollution and effectively utilizing solar energy. It can directly use the solar energy at room temperature to excite photocatalytic reaction of semiconductor photocatalytic materials. However, there are still some key problems in science and technology for the semiconductor photocatalytic technology based on conventional TiO2 photocatalytic materials, such as narrow light response range, low utilization rate of solar energy, easy recombination of photoinduced electrons-holes pairs and low quantum efficiency, etc, which severely limit its wide applications in industry. Hence, in order to promote the practical applications of photocatalysis technology and to solve the problems mentioned above, TiO2-based photocatalysis materials with unique morphology were prepared by electrospinning, the recombination possibility of photoinduced electrons-holes pairs was reduced, and the photocatalytic performance of TiO2 was improved by composite modified TiO2. In addition, the photocatalytic mechanism was also studied. The research results were obtained as follows:Firstly, tetrabutyl titanate(TBT), polyvinylpyrrolidone(PVP), nickel nitrate hexahydrate(Ni(NO3)2·6H2O) as raw material, anhydrous ethanol and glacial acetic acid as solvent forming the precursor solution. Subsequently, one-dimensional(1D) NiO-TiO2 composite nanofibers were successfully synthesized by an electrospinning combined with calcination in air. The phase structures of materials were characterized by X-ray diffraction(XRD). Field emission scanning electron microscopy(FESEM), as well as the attachment that energy dispersive X-ray spectroscopy(EDX) and transmission electron microscope(TEM) were used to observe the morphology of materials. X-ray photoelectron spectroscopy(XPS) was used to identify the chemical status of elements, N2 adsorption-desorption was used to measure the BET surface area and pore structure of the photacatalyst, UV-visible diffuse reflection(UV-vis) were used to study optoelectronic properties of the samples. The photocatalytic performance of the as-prepared one-dimensional NiO-TiO2 composite nanofibers was evaluated through their photocatalytic H2-production activity under the irradiation of xenon lamp(simulated sunlight) and in methanol aqueous solution(sacrificial agent). Results show that, compared with pure TiO2 nanofiber, the photocatalytic activities of TiO2-based composite nanofibers with a small amount of NiO were obviously enhanced and the amount of NiO could play a significant role in the photocatalytic activities under the same reaction conditions. Among them, the best content of NiO was 0.25 wt%, hydrogen production rate was 377 ?mol h-1g-1, apparent quantum efficiency(QE) was 1.7%. Compared with the pure TiO2, it improved more than 7 times. This was because NiO could also act as effective cocatalyst to reduce the recombination probability of photoinduced electron-hole pairs and lower hydrogen production potential, even in the absence of noble metals(such as Pt). This study presents the process of high-performance photocatalytic materials of NiO-TiO2 composite nanofibers with one-dimensional structure prepared by simple electrospinning and also studys the possibility of using cheap transition metal oxide to replace noble metal as cocatalyst in photocatalytic hydrogen. In addition, compared with TiO2 nanopaticles, one-dimensional nanofibers obtained by electrospinning with unique structure is advantageous to the separation and recycling in practical application.Secondly, Graphene, nanomaterials of piled up by the monolayer of carbon atoms into a two-dimensional(2D) honeycomb structure, has a large specific surface area, fast charge migration rate, good heat conduction ability and high mechanical strength, etc. Therefore, the preparation and applications of graphene-based composite nanomaterials have attracted great attention. TBT, PVP, graphite oxide as raw materials, anhydrous ethanol and glacial acetic acid as solvent forming the precursor solution. Subsequently, the reduced graphene oxide-titanium oxide(RGO-TiO2) 1D composite nanofiber was successfully synthesized by an electrospinning combined with calcination in air. Then the obtained samples were characterized by a series of instruments including XRD, FESEM, TEM, BET, UV-vis and thermogravimetric analysis(TGA), and others. We studied the effect of addition amount of RGO on photocalytic H2-production from water splitting in the absence of noble metals(such as Pt) as cocatalyst. The result showed that after modification of RGO, the photocatalytic H2-production performance of TiO2 has been greatly improved. Among them, the best content of RGO was 0.25 wt%, the optimal production rate was 149 ?mol h-1g-1, apparent quantum efficiency was 0.75%. Compared with pure TiO2 nanofiber, it improved more than 10 times under the same reaction conditions. Due to the introduction of RGO, which could effectively increase the specific surface area of samples, as electrons receiver and play a role in accelerating its transfer and effectively separate photoinduced electron-hole pairs, enhance photocatalytic activity. Photocatalytic reaction mechanism was proposed and further confirmed through transient photocurrent response. |
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