| Ti O2 has been considered as the most promising material and extensively application due to its high physical and chemical stability, good performance of acid-base resistance, poorly soluble in water, non-toxicity, lowcost, rich source, wide band gap and electrons and holes of photoproduction have very strong oxidation reduction performance and excellent photocatalytic activity. However, Ti O2 powder as photocatalyst present some disadvantages. First of all, Ti O2 powder easy condensation and particles in suspension are too difficult to be removed from aqueous phase. It is also harmful to regeneration and recycle of catalysts. Furthermore, the catalyst particles may become a cause of turbidity in the drainage as a secondary pollutant. Secondely, Ti O2 can only be stimulated under UV-light due to its wide band gap(Ebg = 3.2 e V) to carry out the photocatalytic reaction. It is unfortunate that the UV-light is less than 5.0 % of solar spectrum, while the near-infrared-light(~ 44%) and visible-light(~ 48%) in solar spectrum can not be utilized by Ti O2, which results in photocatalytic activity of Ti O2 under the solar light is too low.In the past few years, we have been engaged in the research of Ti O2 combined with up-conversion luminescence agents to perform photocatalytic degradation of organic pollutants and photocatalytic hydrogen evolution under the simulated visible-light and achieved some results. It can be attributed to the presence of up-conversion luminescence agents which can emit one high-energy photon(UV-light) by absorbing two or more incident low-energy photons(visible-light). The composite catalyst can absorb ultraviolet light also can absorb visible light, that is, the absorption spectrum of Ti O2 was broaden and oxidation reduction ability of the electrons holes pair remain the same. In order to solve the separation and regeneration of photocatalyst, Ti O2 have been supported on different substrate materials as thin films or membranes carried out the photocatalytic reaction. Since the principle between the photocatalytic degradation and photocatalytic hydrogen production has a certain complementarity. We think hydrogen evolution and pollution degradation can be carried out simultaneously in the same system. 3+In this study, the up-conversion luminescence agent, Er:YAl O3 and Er3+:Y3Al5O12, were synthesized by sol-gel method and its corresponding visible-light photocatalysts, Er3+:YAl O3/Ti O2 membrane, Er3+:YAl O3/Pt-Ti O2 membrane, and Er3+:Y3Al5O12/Pt-Ti O2 membrane Support on different substrates were successfully prepared via sol-gel dip-coating and Sol-gel-hydrothermal. The upconversion luminescence agent and photocatalysts membrane were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy(EDX). This paper mainly studies the following contents. Firstly, through the ultraviolet-visible absorption spectrum calculate the degradation rate of dyes on the presence of different catalysts to compare photocatalytic activity in those catalysts. Secondly, the feasibility of producing hydrogen from biomass used the Er3+:YAl O3/Pt-Ti O2 membranes as a photocatalyst under visible-light irradiation was studied. Finally, studing the Er3+:Y3Al5O12/Pt-Ti O2 membranes broad-spectrum photocatalytic activity to photocatalytic hydrogen evolution with simultaneous different pollutant treatment under visible-light driving. In addition, mass ratio, heat-treated temperature, heat-treated time and initial solution p H as principal influence factors on the photocatalysis capability of photocatalysts membranes were studied. The stabilization and broad-spectrum properties were also included in consideration.Through the research on properties of photocatalyst capable of responding to visible light, we find that the up-conversion luminescence agent combine with Ti O2 to prepare new photocatalysts membranes have very good photocatalytic activity to photocatalytic hydrogen evolution with simultaneous pollutant treatment. Furthermore, the membranes are recyclable. Therefore, these novel composite membrane photocatalysts will have wide applications for photocatalytic hydrogen evolution with simultaneous wastewater treatment on practical application. |
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