| Environmental pollution and energy crisis are two major problems restricting the development of current society.Photocatalysis,a green technology,has promising applications in the fields of environment and energy.It is expected to become one of the most effective ways to solve environmental pollution and energy crisis which are two issues in current society.Until now,photocatalysis has been applied in the degradation of organic pollutants and the evolution of H2 from water,but the key lies in the search and design of the efficient and stable photocatalysts.Among various kinds of photocatalyst,the transition metal oxide semiconductors have become a kind of high-profile photocatalyst due to their easy accessibility,appropriate band edge position and good maneuverability,such as TiO2,Fe2O3,CuO/Cu2O,ZnO,WO3,et al.Among them,TiO2 is recognized as the best photocatalyst because of its superior physical and chemical stability,corrosion resistance,suitable redox potential,non-toxic and low cost.However,the large-scale application of TiO2 for photocatalysis is limited by its large band gap,only absorption ultraviolet light,and easy recombination of photogenerated carriers.In order to efficiently utilize the sunlight,it is necessary to develop visible-light-driven TiO2 photocatalyst.Recently,using metal-organic frameworks(MOFs)as hard templates to prepare the metal oxide semiconductor gained attentions of scientists.MOFs can be used as substrates to obtain porous materials and its band structure also can be modified by tunning the ligands and central metal ions,therefore realizing the in-situ modification of metal oxide semiconductor.Currently,the preparation of metal oxide semiconductor via calcining MOFs has demonstrated its unique advantages.In the process of MOFs’ pyrolysis,metal ions can be converted into metal oxide,and the non-metallic element in ligands such as C,N,S,F,can be doped in metal oxide to modify the photocatalyst at molecular level by controlling the heat-treatment condition.In this thesis,MOFs were used as the hard templates to synthesize the nano-porous metal oxide photocatalysts with visible light response.The details are summarized briefly as follows:(1)Using solvothermal method to synthesis MIL-125(Ti)-NH2;MOF as the self template to control the particle size and morphology of nanoporous TiO2 sample by adjusting the calcination atmosphere sush as the ratio of nitrogen and oxygen,flow rate,heating rate,the calcination temperature,temperature holding time etc.The obtained TiO2 not only can keep the original polyhedron morphology and porous of MOF,but also has large BET surface(389.8 m2/g)because of the escaping of gas from MOF.We also found,in the process of calcinations,the amino groups of MOF’s ligands was introduced as source of nitrogen to get self N-doped TiO2.And the elemental mapping images in Figure a further indicating that N element is homogeneously distributed on the TiO2 The obtained N-TiO2 exhibited superior photoactivity toward H2 evolution under visible light irradiation.Its photocatalytic activity was 19 times higher than N-doped TiO2,which was preparaed by the traditional method.(2)We synthesized MIL-53(Fe)by solvothermal method.Using MIL-53(Fe)as the self template,we successfully fabricated nanoporous α-Fe2O3 sample via calcination method,during which the particle size and morphology of nanopartials are achieved.The obtained α-Fe2O3 had a large surface area of 198.2 m2/g and uniform particle size,advoding the aggregation,which endowed it a superior photocatalytic activity... |
PDF Full Text Request