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    Home > Research group of Professor Xu hangxun of University of science and technology of China: a new way to realize photocatalytic hydrogen peroxide synthesis by structural control of covalent triazine framework materials

    Research group of Professor Xu hangxun of University of science and technology of China: a new way to realize photocatalytic hydrogen peroxide synthesis by structural control of covalent triazine framework materials

    • Last Update: 2020-01-08
    • Source: Internet
    • Author: User
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    As a common green oxidant, hydrogen peroxide is widely used in chemical synthesis, wastewater treatment and other industrial production and life fields In recent years, using solar energy to produce hydrogen peroxide through semiconductor catalyst has become a potential green and pollution-free way However, at present, the photocatalytic efficiency of semiconductor photocatalyst is low and the atom utilization rate is low The main challenge is that it is difficult to realize the two electron process to oxidize water to generate hydrogen peroxide Recently, Xu hangxun, Professor of University of science and technology of China, developed a new alkynyl functional covalent triazine framework material for highly efficient photocatalytic synthesis of hydrogen peroxide, and realized a new route for the synthesis of hydrogen peroxide by two electron process oxidation The results show that the introduction of alkynyl group can regulate the electronic structure of the covalent triazine framework material and promote the efficient use of photocatalysis photo generated charge; at the same time, alkynyl group can be used as the active site of water oxidation and reduce the intermediate state energy barrier of water oxidation in the two electron process, thus realizing the simultaneous reduction of oxygen and water oxidation to produce hydrogen peroxide, thus realizing the photocatalytic synthesis reaction of 100 %Atomic utilization Relevant results were published online in a advanced materials (DOI: 10.1002 / ADMA 201904433) Prof Xu hangxun's brief introduction to the research group since its establishment, the research group has mainly focused on the development of new functional polymer materials, and is committed to the deep understanding of the intrinsic characteristics of functional polymer materials from the interdisciplinary perspectives of chemistry, physics, mechanics, and so on, and further exploring its applications in energy conversion, flexible electronics, energy dissipation and other fields Prof Xu hangxun, professor and doctoral supervisor of School of chemistry and material science, University of science and technology of China In 2006, he graduated from China University of science and technology with a bachelor's degree, and in 2011, he graduated from the Department of chemistry of the University of Illinois at Urbana Champaign with a doctor's degree, under the guidance of Professor Kenneth s Suslick After graduation, he engaged in postdoctoral research in the Department of materials science and engineering at the University of Illinois at Urbana Champaign, and studied in the field of flexible electronics from Professor John A Rogers, academician of the American Academy of Engineering / Academy of Sciences / School of art and science Since independently engaged in scientific research, he has published a number of correspondents' papers in high-level academic journals such as J am Chem SOC., adv mater., angelw Chem., SCI Adv., and many scientific research achievements have been selected into ESI high impact papers At the same time, a number of academic research results were reported by science website, Xinhua news agency and other news media Cutting edge research achievements: covalent triazine framework material structure regulation to achieve a new path of photocatalytic hydrogen peroxide synthesis Covalent triazine framework materials (ctfs) is a kind of semiconductor photocatalytic materials with unique structure, whose chemical and electronic structures can be designed and regulated at the molecular level Through the monomer design, the author can introduce different alkynyl structures into the covalent triazine framework materials, and obtain the alkynyl functionalized ctfs by acid catalyzed polymerization (Fig 1a) In the synthesis process, no metal catalyst is added and the reaction temperature is low, which avoids the residual of metal catalyst and carbonization caused by high temperature At the same time, the obtained two-dimensional structure can expose more active sites, have better photo responsiveness and higher photo generated charge separation efficiency (Fig 1b) Fig 1 (a) synthesis route and structure diagram of ctfs; (b) tem photos of ctfs nanofilms (source: Advanced Materials) then, the energy band structure of ctfs was characterized by UV-Vis diffuse reflectance spectroscopy and synchrotron radiation photoelectron spectroscopy (Fig 2a and 2b) The results show that the energy band structure of the three materials conforms to the thermodynamic reduction of oxygen to hydrogen peroxide, so they can realize the photoreduction of oxygen to hydrogen peroxide At the same time, the oxidation potential energy of ctf-eddbn and ctf-bddbn are higher than that of ctf-bpdcn, indicating that the introduction of alkynyl group gives them stronger oxidation ability The results of photocatalytic performance test show that in pure water saturated with oxygen, the unit rate of photocatalytic hydrogen peroxide production of ctf-eddbn and ctf-bddbn is 2 and 3.4 times of that of ctf-bpdcn, respectively (Figure 2C) It is worth mentioning that the conversion efficiency of ctf-bddbn from solar energy to chemical energy under simulated sunlight can reach 0.14% What's more interesting is that when sodium iodate is used as electron sacrificial agent in argon, CTF bpdcn without alkynyl structure oxidizes water to generate oxygen through four electron process, while ctf-eddbn and ctf-bddbn oxidize water directly to generate hydrogen peroxide (Figure 2D) The above comparison verifies that ctfs with alkynyl function and CTF without alkynyl group In the process of photocatalytic water oxidation, the reaction path is totally different Fig 2 (a) UV-Vis diffuse reflectance spectrum and corresponding tauc curve of ctfs; (b) energy band structure of ctfs measured by synchrotron radiation photoelectron spectroscopy; (c) time performance curve of hydrogen peroxide production by ctfs in oxygen saturated pure water; (d) oxygen and hydrogen peroxide production by ctfs in 0.01 M sodium iodate solution in argon atmosphere Time performance curve of (source: Advanced Materials) in order to further explore the influence of alkynyl introduction on the catalytic pathway of water oxidation of c-tfs materials, the first principle calculation, in-situ spectral characterization and isotope labeling experiments were conducted in-depth study The intermediate state of OH * is an important intermediate state for the oxidation of hydrogen peroxide by two electron processes The calculation results show that when the benzene ring and triazine ring in ctfs are the active sites of the water oxidation reaction, the Gibbs free energy required to generate the intermediate state of OH * is very large, which is not conducive to the generation of hydrogen peroxide (Fig 3a and 3b) However, when the alkynyl structure in ctf-eddbn and ctf-bddbn is the active site of the water oxidation reaction, the Gibbs free energy for the formation of OH * intermediate state is significantly reduced to realize hydrogen peroxide production by two electron process (Fig 3C and 3D) In addition, free radical capture experiments and electrochemical tests further confirmed that ctf-eddbn and ctf-bddbn photocatalytic water decomposition is a direct two electron process Fig 3 (a) Gibbs free energy diagram of hydrogen peroxide production when benzene ring in ctfs is the active site; (b) Gibbs free energy diagram of hydrogen peroxide production when triazine ring in ctfs is the active site; (c) Gibbs free energy diagram of hydrogen peroxide production when alkyne group in ctf-eddbn is the active site; (d) ctf-b Gibbs free energy diagram of hydrogen peroxide production when the alkynyl group in ddbn is the active site (source: a advanced materials) to sum up, the author reported a kind of nonmetallic alkynyl functionalized covalent triazine framework material, and realized high-efficiency catalytic water oxidation and oxygen reduction to produce hydrogen peroxide under visible light At the same time, the mechanism of the direct two electron oxidation of hydroperoxides by alkynyl functionalized covalent triazine framework materials is elucidated, which provides new ideas and insights for the design and synthesis of polymer catalysts for solar energy conversion at the molecular level The research team of Professor Wu Xiaojun, Department of materials science and engineering, University of science and technology of China, provided theoretical calculation support for the research The research results were published on advanced materials (DOI: 10.1002 / ADMA 201904433) under the title of "acetylene and diacetylene functional triazine frameworks as metal free photocatalysts for hydrogen peroxide production: a new two electron water oxidation pathway" Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.
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