The Research On Defects,Morphology Engineering And Co-catalysis Strategies For Improve Photocatalytic Performance Over Bi₂O₃,CdS Semiconductor

The energy crisis and environmental issues are the important challenges that determine the sustainable development of mankind.The use of photocatalytic technology to develop clean energy is an important solution to these problems.Solar energy can be converted into clean energy and necessities for production and life required by mankind by utilizing solar energy to convert the earth’s rich H2O and N2 into O2,H2 and NH3.The semiconductor photocatalyst has been widely studied due to its special properties,and it can play a vital role in photocatalytic technology.However,the low utilization of visible-ight,recombination of photo-generated electron-hole pairs,and unfavorable reverse reactions affect the application of semiconductor materials in photocatalysis.In this thesis,two common Bi2O3 and CdS semiconductor materials are studied,defect engineering,morphology engineering and co-catalysis strategies are used to improve the photo-generated carrier transport rate,suppress the recombination of electron-hole pairs,and enhance light absorption,thereby improving the photocatalytic performance.The main research contents and results of this article are as follows:(1)Bi2O3 nanosheets synthesized by one-step hydrothermal method were used as research objects.Oxygen vacancy-rich BiO2-x ultra-thin nanosheets(BiO2-x UTNSs)were prepared by physical ultrasonic stripping.The photocatalytic water-splitting performance with methyl viologen as sacrificial agent was studied,and the photocatalytic water-splitting oxygen generation without cocatalyst was realized.The good absorption of visible-light was found by changing the wavelength of the light;the samples show the best performance when the mass ratio of the sacrificial agent and the catalyst was 1:10.The oxygen vacancies and ultra-thin morphology in BiO2-x ultra-thin nanosheets are the result of combining defect engineering and morphological engineering,which enhanced the light capture ability,reduced the band gap width,increased the valence band position,and increased the number of reactive sites.And the photocatalytic water splitting oxygen generation performance of Bi2O3 without precious metal co-catalyst was successfully improved.(2)The unique 1D/2D CdS@Ti3C2 composites material was prepared by CdS growing in situ on the surface of Ti3C2 MXene obtained by HF acid etching as a substrate with a one-step hydrothermal synthesis method.Among them,1D CdS nano wires are wrapped on the surface of 2D multilayer accordion-like Ti3C2 MXene.Under simulated sunlight,the optimal composite ratio of CdS@Ti3C2-15 composite showed photocatalytic hydrogen production activity of 3176.38μmol h-1g-1 and nitrogen fixation activity of 14.653 mmol L-1 h-1 g-1,and the photocatalytic activity of CdS@Ti3C2-15 composites is much better than pure CdS and CdS@Pt(0.1 wt%).Ti3C2 is the role of co-catalyst in 1D/2D CdS@Ti3C2 composites which successfully combined morphology engineering and co-catalyst strategies to achieve an efficient photogeneratcd electron transport rate,effectively inhibited the recombination of photogenerated electron-hole pairs,and significantly improved light absorption capacity.The improvement of photocatalytic water splitting hydrogen production performance and photocatalytic nitrogen reduction performance of CdS without noble metal co-catalyst was successful.(3)2D sulfur vacancy-rich 1T-MoS2(SV-1T-MoS2)was prepared by a simple one-step hydrothermal method,and the content of sulfur vacancy and 1T phase was adjusted by controlling the ratio of Mo precursor and S precursor.Then,CdS nanorods were prepared by one-step hydrothermal synthesis.Sulfur vacancy-rich 1T-MoS2 as co-catalyst was combined with CdS to form 2D/1D sulfur vacancy-rich 1T-MoS2-CdS(SV-1T-MoS2-CdS)composites material by using physical ultrasound method.SV-1T-MoS2 nanosheets were distributed around CdS nanorods to formed a 2D/1D structure.Thus,SV-1T-MoS2-CdS composites combined defect engineering,morphology engineering and co-catalyst strategy.The optimal proportion of 30 wt%SV-1T-MoS2-CdS composite showed excellent photocatalytic nitrogen fixation performance(8220.83 μmol L-1 h-1 g-1),and the co-catalytic effect of SV-1T-MoS2 is 2.36 times that of the precious metal Pt.The sulfur vacancy-rich and more 1T phase in SV-1T-MoS2 of SV-1T-MoS2-CdS composite provide more active edge sites,enhanced conductivity,improved light absorption,and improved photocarrier separation and transfer capabilities.As a result,the photocatalytic performance is significantly improved.The photocatalytic nitrogen reduction performance of CdS without precious metal co-catalyst improved successfully.