| Constructing anatase TiO2-based hierarcal structure to improve its solar energy conversion and photocatalytic oxidation efficiency is one of the important methods to solve the increasingly serious energy shortage and environmental pollution problems.In this thesis,the photocatalytic hydrogen production,photodegradation of dye and photoreduction of CO2 performance of anatase {001} TiO2 nanosheets was improved by combining TiO2 with g-C3N4 and further gold-copper alloy nanoparticles(NPs)modification.The main research results and innovations are as follows:(1)A series of gram-level heterostructured hybrids {001} TiO2/g-C3N4-x(abbreviated as TC-x,x:amount of g-C3N4,mg)were fabricated by solvothermal method using diethylenetriamine as capping and morphology control agent.The nanosheet hierarchical spheres morphology of single{001}TiO2(18.26%{001} facets)is gradually disappeared as g-C3N4 contents increases(x=50,100,150,175 and 200),and more and more TiO2 nanosheets are vertically staggered grown on both sides of the g-C3N4 layers.All the hybrids exhibits higher photocatalytic H2 evolution rate(HER)than {001}TiO2,and the TC-175(19.87%{001})presents highest photocatalytic hydrogen evolution rate(HER)of 26.20 mmol·g-1·h-1,which is the highest value of the currently reported Ti2/g-C3N4 catalysts,and it even shows HER of 341.67 ?qmol·g-1 h-1 under visible light,consistent with the most uniform ultrathin nanosheets(60-100 x 7-11 nm)array-like morphology and the largest surface area(146 m2/g)of TC-175.Meanwhile,TC-175 also shows the highest photodegradation activity for(kapp=0.064 min-1)Rhodamine B under visible light.These findings can be explained by the highest separation efficiency of photogenerated electron-holes promoted by TiO2-g-C3N4 interface and {001}-{101} TiO2 surface heterojunctions of the hybrids,the lower band gap of 2.96 eV and the high quantum efficiency of 4.2%at 420 nm resulted from remarkable TiO2-g-C3N4 two-phase synergistic effect associated with the most uniform nanosheet-like morphology.(2)A series of gold-copper alloy NPs modified heterostructured photocatalysts AuCuy/TC(TC represents TC-175,y(Cu/Au molar ratio)=0.33,1,3 and 4)was prepared by deposition reduction method.With the increase of Cu/Au molar ratio,the size of alloy NPs decreased from 5.6±1.03 nm to 3.2±0.77 nm,and the alloy NPs are mainly dispersed in the edge of the TiO2 nanosheet in the TC hybrids.The series of AuCuy/TC heterostructured photocatalysts show better activity for photocatalytic reduction CO2 by H2O than TC hybrids.AuCu3/TC shows the highest CH4 formation rate of 74.33 ?mol·g-1·h-1 and photogenerated electron selectivity of 83.21%,far higher than the results of most current TiO2-based catalysts,due to the most surface OH amount promoting the adsorption of CO2,strong interaction between gold-copper alloy NPs and TiO2 nanosheets leading to the enhancement of visible light absorption and the effective separation of photogenerated electron-hole pairs ascribed to metal-semiconductor schottky junction,and the enhanced photocatalytic efficiency of the TC hybrid substrate. |
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