China University of Science and Technology non-catalytic hydrogenation of vanadium dioxide phase transition has been progress

Vanadium dioxide is a strongly associated transition metal oxide material with a wide range of applications, the most notable feature of which is an insulation-to-metal phase change of four to five orders of magnitude at 68 ° C. The various photovoltaic functional properties of VO2 Are all closely related to their phase transformation, however, their relatively high phase transition temperature has become a big bottleneck in practical application.By in-depth study of the phase transition microscopic mechanism and to explore effective phase change control methods to reduce the phase transition temperature to promote its actual Application is of great significance.Hydrogen atoms due to its small atomic radius can effectively enter the VO2 lattice electron doping, to achieve the purpose of regulating the phase transition.Using the traditional high temperature precious metal catalytic hydrogenation method, the University of Science and Technology of China Synchrotron Radiation Laboratory Zou Chongwen Research Group and the National Research Center for Microscale Materials Science Jiang Jun research group in the VO2 thin film to achieve a three-phase phase transition from insulation - metal - insulation and reveals the hydrogen-induced electron doping vO2 conduction band energy (Phys. Rev. B 96, 2017, 125130). However, conventional hydrogenation doping techniques rely on conditions of high energy consumption such as temperature and pressure, To expensive precious metal catalyst, and the hydrogenation of the catalytic material deposited on the surface of the metal is also difficult to remove, these adverse factors become restrictions on VO2 material hydrogenation phase transition regulation and application of obstacles.

Recently, the researchers broke through the traditional method of catalytic hydrogenation of high temperature precious metals to control VO2 phase transition, and realized the use of metal adsorption-driven acid solution proton doping into the VO2 material to achieve very low cost of material hydrogenation under mild conditions, invented the 'point Iron into hydrogen 'technology.

Acid solution is easy to corrode most of the oxide including VO2, so under normal temperature and pressure conditions, acid can not be used as a hydrogen source for hydrogenation of oxide materials.Experimental researchers found that the metal with the appropriate work function When the particles come into contact with the VO2 film and are put into the acid solution, the VO2 film is not only not corroded by the acid solution, but rather rapidly hydrogenated and induced phase transformation. This phase change process has an extremely rapid diffusion effect, Metal particles (1 mm in diameter) can make a VO2 epitaxial film with a diameter of two inches resistant to corrosion and metalization, thus achieving the effect of 'spotting iron to hydrogen' similar to 'pitting into gold.' Theoretical predictions reveal that the electron behind the phenomenon - Proton-Co-doping Mechanism When the low work function metal contacts the high work function VO2, the electrons spontaneously inject into the VO2. Due to the electrostatic induction effect, the protons in the acid solution are pulled into the VO2 to make the VO2 metallized So that the formation of oxygen vacancies can be greatly improved, which can prevent acid corrosion.On the basis of VO2 metallization, if the use of lower work function metals such as Al, Zn, etc. can continue to inject More electrons and protons, filling the new valence band with electrons to form a new insulation state, and achieving phase transition from insulation to metal-insulation in turn.

The electron-proton doping strategy achieves the intrinsic insulation state-metal state-new insulation state tri-state adjustment by simply contacting the acid solution, the metal particles and the VO2, not only to a compatible conventional environment Of the doping method can also have a positive impact on the study of electronic synergies.Modification of the material has been the focus of physical, chemical and material science research, in which doping is one of the most effective method.Based on the electronic - Proton doping principle, the researchers will be replaced by acid solution of lithium ions, extended into the electron - ion co-doping strategy, the same lithium ion doping and regulate the phase transition behavior of VO2. Further also found that the strategy More doping hydrogenation of oxide materials, such as TiO2, is demonstrated, confirming the universality of this doping technique, which is often catalyzed by high temperature, high pressure, and noble metals The Institute developed a better compatibility with conventional mild environment of the doping mode, and the operation is very simple and low cost, the development of new functional materials and devices and to promote the development of basic theory Significance.

Relevant research results published in the "Nature - Communications", doctoral student Chen Yu-grain, visiting scholar Wang Zhao Wu as co-author, associate researcher Zou Chongwen, Professor Jiang Jun as the author of this study has been the national key basic research and development program for young people Special projects of scientists, NSFC, special funds for basic scientific research service of Central Universities and funding of the Chinese Academy of Sciences for Youth Innovation Promotion.