| With the rapid development of human society and dramatically consumption of traditional energy,energy shortage has become a crucial factor restricting the sustainable development of human society.And the overuse of fossil fuels has resulted in serious demage of ecology and environmental pollution in the world.Therefore,developing clean and environmentally friendly renewable energy system has drawn much attention and become the first priority strategy in the world.Semiconductor-based photocatalytic hydrogen production which converts the sustainable clean and renewable solar energy into chemical energy can relieve the crisis of energy shortage and environmental pollution,has become one of the most promising technology in the world.TiO2 semicocnductor has been widely used in photocatalytic field because of its excellent photoelectric conversion efficiency,high chemical stability,nontoxicity and low cost.Since the pioneer work conducted by Fujishima and Honda,a series of significant progress has been made in semiconductor-based photocatalysis and a deeper understanding of photocatalysis has been realized during the past fifty years.However,light absorption ability and carrier separation efficiency of semiconducting materials remain dissatisfactory,restricting the further improvement of photocatalytic activity of the system.In this thesis,we focused on developing TiO2-based multi-component photocatalysts by modifying TiO2 with different methods in the aim to expand the light absorption of TiO2-based photocatalytic systems,and also focused on improving the photo-generated charge separation efficiency.The photoelectric properties of the nanocomposite photocatalysts were characterized and the photocatalytic mechanism were further explored.While enriching the semiconductor photocatalytic system,the understanding of semiconductor photocatalysis is deepened,which may provide a direction for the further development of semiconductor photocatalysis.The main progress and results of this dissertation are as follows:1.SrTiO3-TiO2 hetero-nanoparticle modified TiO2 nanotube arrays(ST-TiO2 NTAs) were constructed by partially converting the amorphous TiO2 nanoparticles into SrTiO3 via hydrothermal method.The SrTiO3-TiO2 nanotube arrays(S-TiO2 NTAs)were also prepared by directly hydrothermal treatment of amorphous TiO2 NTAs for comparison.The photoelectrocatalytic hydrogen production activities of all the samples were evaluated by using ethylene glycol as a sacrificial reagent in water under a 300 W xenon arc lamp.The ST-NTAs photoanodes prepared by hydrothermal treatment for 1.0 h exhibited the highest photoelectric activity.At a bias of 0.3 V(vs SCE),the photoelectrocatalytic hydrogen production rate of ST-TiO2 NTAs was 2.1 times higher than that of the unmodified TiO2 NTAs.Compared to S-TiO2 NTAs,ST-TiO2 NTAs showed a 32.8%increase in hydrogen production rate.2.Bi2S3 nanoparticles were efficiently deposited on TiO2 nanotube arrays(BhS3-TNTAs)by sequenial chemical bath deposition(CBD)method to enhance visible light response of pure TNTAs.Notably,a high-throughput screening method of scanning photoelectrochemical microscopy(SECM)was exploited to screen and find out the optimized photoelectrochemical photoanode.The effects of Bi2S3 nanoparticles on visible light absorption and photoelectrocatatlytic hydrogen production rate of TNTAs were investigated in detail.When adopted as photoanode,the optimized heteroelectrode exhibited a more than 13-fold enhancement in hydrogen production rate under visible light irradiation.The electrochemical impedance spectroscopy(EIS)and photoluminescence(PL)characterizations showed that the superior photoelectrocatalytic activity of Bi2S3-TNTAs composites were attributed to the enhanced light absorption and separation of photo-generated charges.3.To enhance photoelectrocatalytic efficiency,an ordered one-dimentional heterojunction photocatalyst consisting of CuxZn1-xIn2S4 ultrathin nanosheets on electrochemically anodized TiO2 nanotube arrays(CuxZn1-xIn2S4@TNTAs)was successfully synthesized by solvothermal reaction.The effects of different Cu doping amount on the morphology of CuxZn1-xIn2S4 nanosheets and the light absorption of CuxZn1-xIn2S4@TNTAs composite were investigated.It was found that the CuxZn1-xIn2S4 ultrathin nanosheets on TNTAs significantly enhanced visible light absorption and photoelectrochemical response,and a near 8.0-fold increase in photoelectrocatalytic hydrogen production rate was achieved compared to that of the blank TNTAs.Moreover,the CuxZn1-xIn2S4@TNTAs exhibited the excellent photoelectrocatalytic stability.The measurements of Flat-band and electrochemical impedance revealed the feasibility of charge transfer in CuxZn1-xIn2S4@TNTAs hetero-system,supported by PL and photoelectrochemical measurements.The superior photoelectrocatalytic activity of CuxZn1-xIn2S4@TNTAs composite electrode were mainly attributed to enhanced light absorption and separation of photo-generated charges,and facilitating electron transport along the 1D TiO2 structure.4.The transparent TiO2 film(TiO2 Slide)was prepared by applying TiO2 colloids,which were prepared by sol-gel method,onto a slide.Then,Pt and BoPt dyads were loaded on TiO2 Slide by using methyl phosphate as anchoring group.The photogenerated carrier behavior of the dye-sensitized TiO2 systems was investigated via femtosecond transient absorption spectroscopy by pumping the chromophores at 600 and 505 nm.The kinetic curves of photogenerated carriers were obtained by global fitting,and the relaxation process of the photocatalytic systems after photoexcitation was analyzed.When excited,the Pt was found to go from the ground state to its 1MMLL'CT singlet excited state,followed by two ultra-fast competitive processes of electron transfer to TiO2 and conversion to the 3MMLL'CT triplet excited state.When attached with Bodipy organic dye,the 1MMLL'CT singlet excited state electrons transferred to TiO2 in 0.6 ps,and the long-lived Bodipy(+)-Pt(bpy)-TiO2(-)charge separation state was formed by the hole transfer from Pt to Bodipy.When BoPt was excited,it gone from the ground state to its 1??*singlet excited state.Subsequently,the chromophore gone into 1MMLL'CT singlet excited state by SEnT,and two competing processes of electron transfer and ISC occurred.Finally,a long-lived Bodipy(+)-Pt(bpy)-TiO2(')charge separation state with lower energy was formed in 661 ps from Bodipy-Pt(bpy)(+)-TiO2(-)charge separation state through the hole transfer process from Pt to Bodipy after interfacial charge transfer.It indicated that by linking Bodipy organic dyes on charge separate Pt chromophore with low molar extinction coefficient to construct multi-chromophores,the photo-absorbing efficiency of the system can be improved while prolonging the lifetime of photo-generated carriers,which can be expected to improve the solar conversion efficiency of the system. |
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