The Development And Application Of New Type Of Nanometer Catalytic Materials

Photocatalysis, as a novel technique, aims at effectively convertingenvironmental-friendly and abundant solar energy into chemical andelectrical energy, and solving the global problems of energy crisis andserious environment pollution to realize the substantial development ofsociety. As a typical semiconductor, titanium dioxide has attractedlasting concern due to its low toxicity, low cost, excellent chemicalstability and high activity. However, as a result of its wide band gap, UVlight excitation and low quantum efficiency （QE）, the practicalapplication of TiO₂has been prohibited. For these resons, the followingthree routes were proposed:1) modifying TiO₂with carbon throughnovel technique to extend its light absorption edge to visible region;2)developing high-efficiency visible-light photocatalyst for enhancing theutilization efficiency of solar light based ondvanced visible-lightphotocatalysis technology;3) Fabricating high IR-absorption catalyst,inducing the catalytic degradation of pollutants in dark and achievinground-the-clock catalytic treatment of contaminants. For the abovereasons, this graduation thesis mainly includes the following three parts.Ethanol supercritical route for fabricating bimodal carbon modifiedmesoporous TiO₂with enhanced photocatalytic capability indegrading phenol.In this section, we fabricated mesoporous bimodal carbonmodified TiO₂via supercritical solvothermal approach using raw rice ascarbon source. In virtue of XRD, TPO, XPS, Raman and etc, we verifiedas-prepared C-TiO₂to possess a bimodal carbon-modificationincluding carbon doping in the lattice of TiO₂and hybridized carbononto the surface of TiO₂. Morover, UV-vis DRS, BET and HRTEMcharacterizations results showed that the ethanol supercriticaltreatment also contributed mesoporous structure, small crystal size, large special surface areas, high crystallinity of anatase of C-TiO₂andhigh visible-light absoption. Besides, we also investigated bimodalcarbon modification synergic effect for treating phenol. Thus, thesefunctional catalysts exhibited high photocatalytic performance andexcellent recyclability for phenol degradation under visible-lightirradiations （λ>420nm）.（2） Supercritical approach synthesis of ZnxCd1-xS with extremelyexcellent photostability in photocatalytic H2evolution and organiccompounds removalIn this part, mesoporous nano-spherical ZnxCd1-xS photocatalystwas prepared by supercritical approach in the absence of surfactantsor structure directing agents. Through XRD, TG-DTA, BET and HRTEMchacacterizations, we proved that the as synthesized ZnxCd1-xS bysupercritical technique showed mesoporous structure, small anduniform crystal size, large special surface areas, high crystallinity andhighly excellent thermal stability. Furthermore, XPS and UV-vis DRS resultsexhibited controllable composition of ZnxCd1-xS, leding to the tunablelight absorption edge. Based on the above advantages, ZnxCd1-xSshowed high phototcatalytic degradation yield of4-CP and RhB, andrealized high photocatalytic H2production rate. Meanwhile, onaccount of excellent thermal stability as well as intense interaction of S,Cd and Zn induced by supercritical treatment, it inhibited thephotocrrosion of ZnxCd1-xS, resulting in extremely excellentphotostability.（3） An efficient round-the-clock La₂NiO₄visible-light photocatalystfor breaking down phenolic pollutantsIn this chapter, a novel La₂NiO₄photocatalyst was synthesized byco-alcoholysis of La（NO3）3and Ni（NO3）2under solvothermal conditions.By UV-Vis-IR DRS, XRD, TEM and FESEM test, La₂NiO₄showed layeredperovskite crystal structure with high IR light absorption. It exhibited high activity for mineralizing4-chlorophenol under visible light irradiation andeven in dark, leading to the round-the-clock photocatalysis. Accordingto PL and electrochemical analysis, we proposed the plausiblephotocatalytic mechanism of the La₂NiO₄in the absence of lightirradiation. Both the La₂NiO₄crystals and the organic molecules playedkey roles for organic pollutants degradation process in dark. The4-chlorophenol firstly ionized into anions, followed by donating electronsto La₂NiO₄owing to the positively charged surface. Then, the electronscould react with dissolved O₂to produce?O₂-, which subsequentlyreacted with H+to form?OH radicals. These highly active?OH radicalscould oxidize4-chlorophenol into CO₂, leading to the completedegradation.