Construction Of Micro-nano Materials And Their Application In The Photocatalytic Reactions

Utilization of solar energy is the basic way to solve the energy crisis and environmentpollution by mimicking the photosynthesis existed in nature. Semiconducor materials areproposed as the most promising tools to perform this goal due to their excellent light-electronresponse character. However, they are still suffered from narrow spectral absorbance,recombination of photogenerated electrons and holes and low photocatalytic reaction selectivity,which cause a tardigrade development in the photocatalysis research field. Micro-nanostructurephotocatalyst systems which are usually composed of carrier, electron donor and acceptor （or actas light absorbance）, exhibit effective catalytic activity due to wide spectral absorbance andenhanced charge separation. However, the effection on the photocatalytic activity caused by theelectron donors or acceptors morphology has been ignored for a long time.In this paper, based on the idea of energy up-conversion, morphology controle and spatialconfinement of electron donors and acceptors, we constructed novel micro-nano structurematrials to improve the solar absorbance and charge separation efficiency for the photocatalysis,which were successfully applied in the water water purification, oxidation of olefins and watersplitting.First, to show the influence caused by the morphology of surface electron donors oracceptors, a new kind of carbonouse TiO₂composite, TiO₂-Cdot, was fabricated as the modelphotocatalyst. It indicated that TiO₂particles strewed with optimal quantity of carbon nanodotshas much higher photoactivity than that of TiO₂overcovered with carbon layer owning to thesufficient exposure of the active sites and efficient separation of photogenerated electrons andholes. According to these results, the different photocatalytic mechanism was discussed. Theestablished mechanism is proposed to be compatible to clarify why the semiconductors modifiedwith other electron acceptors such as metal-semiconductor hybrid materials have the optimalcontents for the photoactivity. Moreover, a piston motion model electrons transfer mechanism was proposed for TiO2@C material for the first time, which maybe has the universality to other kind of core-shell semiconductor hybrid materials with compact shells and need further investigation in the future work.Second, we prepared a novel photocatalyst, Pt@TiO.2-TCMnPc, based on TiO2nanotube with confinement of electron donor and acceptor at inner and outer surface respectively by a universal method. In which, Pt nanoparticles （electron acceptor） and dye （TCMnPc, electrons donor） are localized at inner and outer surface of a porous TiO2nanotube respectively. The as-designed nanostructure afforded a void space separation state of electron donor and acceptor, which significantly enhanced the charge separation, consequently the catalytic activity for photooxidation of olefins with O2. Moreove, both of the electron donor and acceptor were utilized as active site to activate the substrates by deliberate design avoiding the use of sacrificial agents.Last, based on the idea of energy up-conversion and band matching, a novel micro-nano structure NaYF4:Yb3+, Er3+@SiO2-CuInS2was fabricated to apply in the photocatalytic water splitting and reduction of CO2. The as-prepared photocatalyst can absorb near infrared light, which improve the utilization efficiency of the solar light. The photocatalytic efficiency and selectivity were remarkably improved.The results reported in this paper as mentioned aboved should be much helpful to make a rational design on constructure new kind of composite photocatalysts.