Preparation And Photocatalytic Performance Of Indium-based Tubular Heterojunction Assisted By MOF

With the speed progress of human society and the promotion of aggiornamento,the impact of environmental pollution and energy shortage is deepening.In view of environmental problems,antibiotic treatment is imminent,and chemical pollutants can generally be reduced by dilution or adsorption treatment.Different from this,the wanton discharge of antibiotics leads to the emergence,mass reproduction and even evolution of drug-resistant bacteria,which creates technical barriers for degradation treatment.At the same time,the depletion of non-renewable energy seriously impedes the pullulation of science and technology and society,and the combustion of some fossil fuels pollutes the atmosphere and seriously endangers the global ecological health.For the shake of settling the above matters,it is necessary not only to effectively degrade pollutants,but also to develop and utilize environmentally friendly renewable energy.It is worth noting that photocatalysis technology takes semiconductor photoelectric conversion as the core.Through photoelectric chemical process,solar energy can be effectively converted into environmentally friendly and efficient hydrogen energy for storage,and at the same time,persistent pollutants can be effectively degraded,that is,environmental pollution and energy shortage can be considered.Among many photocatalysts,In-based compounds（In₂O₃,In₂S₃,etc.）have directed wide attention because of their suitable oxidation/reduction energy band structure and controllable micro-morphology.However,traditional monomer In-based photocatalysts often have many defects,such as the need to improve the light utilization rate,insufficient carrier separation efficiency,easy to produce photo corrosion and so on.In order to improve the photocatalytic activity and practical performance,indium-based semiconductor photocatalyst was modified by regulating the energy band structure,optimizing the appearance,and constructing heterojunction.The idiographic work is as follows:Firstly,indium-based organic framework precursor was prepared by oil bath method,ZIF-67 particles were loaded on its surface by water bath method,and then Co₃O₄nanoparticles/In₂O₃ nanotube heterojunction derived from double MOFs template was obtained by chemical calcination.The effect of loading amount of Co₃O₄ nanoparticles on photocatalytic degradation performance was studied.The results show that Co₃O₄nanoparticles/In₂O₃ nanotube pn junction（Co₃O₄/In₂O₃-3）has obvious enhancement of photodegradation of tetracycline hydrochloride（TC-HCl）compared with single In₂O₃（～6.5 times）and single Co₃O₄（～4 times）,and it has better stability.Therefore,Co₃O₄/In₂O₃nanotube pn junction formed by proper potential gradient can effectively improve carrier transport,including increasing carrier transport,prolonging service life and reducing recombination.Co₃O₄ with narrow band gap can improve solar energy efficiency.In addition,the three-dimensional tubular structure can provide many active sites and increase the photodegradation stability.Secondly,based on the unique structure of MOF,In₂S₃ hollow nanotubes were obtained by simple solvothermal vulcanization of indium-based precursors.Heterojunction was constructed by introducing bimetallic sulfide Cd_0.8Zn_0.2S nanoparticles with matched energy level structure.It was characterized by X-ray diffraction（XRD）,scanning electron microscope（SEM）and X-ray photoelectron spectroscopy（XPS）,and the photocatalytic degradation of antibiotics and hydrogen production from water splitting were studied.By means of a train of photoelectric tests,the mechanism of enhancing its photocatalytic performance was explored.The results reveal that when the loading amount of Cd_0.8Zn_0.2S reached the optimal level,the pollutant degradation rate of Cd_0.8Zn_0.2S/In₂S₃ composite photocatalyst reached 92%within 10 minutes,which was about～10 times and～7 times higher than that of pure In₂S₃and Cd_0.8Zn_0.2S.The results of free active radical trapping experiments illustrate that the key active radical in the catalytic degradation process is superoxide radical（·O₂^-）.On the other hand,the composite photocatalyst has the best photocatalytic decomposition performance of aquatic hydrogen.Under the condition of TEOA as hole sacrificial agent,the hydrogen production rate can reach～3480.91μmol·g^-1·h^-1(～40 times of In₂S₃and～30 times of Cd_0.8Zn_0.2S).At the same time,under the 6-hour cycle test,they all show excellent physical and chemical stability.