| Nowadays,water pollution and energy shortage have become a worldwide problem,and finding effective and sustainable green ways has become a top priority.Among the many feasible methods,photocatalytic degradation of semiconductor materials and hydrogen production have entered the researcher's field of vision with their unique advantages,and have received widespread attention from the scientific community.Most semiconductor materials can be photocatalytically degraded by intrinsic photovoltaic properties under sunlight,effectively treating water pollution.In addition,there are some semiconductor materials with suitable band structures that can directly decompose water to produce hydrogen through photocatalysis.As is known to all,hydrogen energy is a new type of energy with no pollution and high combustion energy,which can replace traditional fossil fuels.It can efficiently alleviate environmental pollution while supplying energy efficiently.Therefore,photocatalytic degradation of semiconductor materials and hydrogen production have become the best choices to solve water pollution and energy shortages.Among many semiconductor materials,titanate-based semiconductor materials have suitable conduction and valence band positions(conduction bands that are negative to the reduction potential of H+ to H2,and valence bands that are positive to the oxidation potential of H2O to O2),high stability has been widely used in the field of photocatalysis in recent years,including manganese titanate(MnTiO3),calcium titanate(CaTiO3)and strontium titanate(SrTiO3).However,due to the intrinsic characteristics of the above materials,the wide band gap limits the utilization of visible light,and the high electron-hole recombination rate limits the efficiency of photo-generated carriers,resulting in its photocatalytic performance cannot be fully exploited.Therefore,how to improve the absorption of visible light by a semiconductor material and the improvement of its photo-generated electron migration rate are important factors for improving the photocatalytic performance of the titanate.Studies have shown that surface modification of semiconductor materials,deposition of cocatalysts,and construction of semiconductor heterojunctions can effectively improve their photocatalytic performance,including increasing the visible light response range and promoting the separation of photogenerated electron-hole pairs.In this thesis,the preparation,modification and application of titanate-based semiconductor composites are studied.The main research contents are divided into the following three parts:(1)MnTiO3 nanowires were prepared by electrospinning,and then AgCl/Ag was loaded on them by photodeposition to prepare AgCl/Ag/MnTiO3 semiconductor composites,in addition,the effect of AgCl/Ag loading on the photocatalytic degradation ability was studied.SEM,TEM,and XRD results showed that AgCl/Ag particles were successfully supported on MnTiO3,and UV-vis results confirmed that the AgCl/Ag loading can effectively expand the response range of MnTiO3 to visible light.It is further known through photocatalysis experiments that AgCl/Ag/MnTiO3 nanocomposite has the best photocatalytic degradation efficiency of RhB(80%degradation within 2h)than that of pure MnTiO3(10%degradation within 2h).The main reason is that Ago is used as the quenching center,and AgCl/Ag and MnTiO3 forms a Z-Scheme structure,which can effectively accelerate the separation and migration of photo-generated carriers and enhance the rate of photocatalytic degradation.(2)MoS2/CaTiO3 semiconductor composites were prepared by a two-step hydrothermal method,and the effect of the quantitative change of MoS2 on the performance of CaTiO3 photocatalytic hydrogen production was investigated.Testing methods such as SEM,TEM,EDS,Mapping,XRD,and XPS were used to confirm that the lamellar MoS2 was successfully supported on the surface of cubic CaTiO3.According to the results of photocatalytic hydrogen production,the optimal photocatalytic hydrogen production of MoS2/CaTiO3 semiconductor composite is about 381.23 ?mol/g·h,which is about 30 times stronger than that of unmodified CaTiO3(13.19 ?mol/g·h).The results are mainly attributed to the fact that lamellar MoS2 can act as a co-catalyst to enable the photo-generated electrons of CaTiO3 to migrate quickly and efficiently,reducing the photo-generated electron-hole recombination rate,and the lamellar MoS2 can provide a larger specific surface area for CaTiO3,more conducive to photocatalytic hydrogen production.(3)SrTiO3 nanospheres were prepared by hydrothermal method,and then g-C3N4 was deposited on the surface of SrTiO3,and further lamellar MoS2 was loaded to form MoS2/g-C3N4/SrTiO3 nanocomposite,the effect of MoS2 and g-C3N4 on the performance of SrTiO3 photocatalytic hydrogen production were studied.The SEM,TEM,XRD and XPS characterization methods confirmed that MoS2 and g-C3N4 were successfully supported on the surface of SrTiO3 nanospheres.According to the experiment of photocatalytic hydrogen production,the hydrogen production of MoS2/g-C3N4/SrTiO3 nanocomposite is approximately 1623.37 ?mol/g·h,which is nearly 30 times the hydrogen production of unmodified SrTiO3(49.66?mol/g·h),which is mainly due to the formation of surface heterojunctions between g-C3N4 and SrTiO3,which can effectively promote the transfer and separation of photo-generated electrons and holes,and that the lamellar MoS2 co-catalyst can accelerate the photo-generated electron migration while increasing the specific surface area further enhances the performance of photocatalytic hydrogen production. |
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