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Recently, Professor Martin's group at the School of Chemistry and Molecular Engineering of Peking University has made important breakthroughs in the research of hydrogen production process in low-temperature industries. The research results are based on Atomic-layered Au clusters on α-MoC as catalysts for the low temperature water-gas-shift reaction. The title was published in the June 22 issue of Science (DOI: 10.1126/science.aah4321).
The water gas shift reaction (CO+H2O=CO2+H2) can take hydrogen from water and is an important reaction of fossil energy and hydrogen production from biomass and purification of hydrogen. Its combination with steam reforming reaction is currently the main industry for low-cost hydrogen production. Technology is widely used in the production of ammonia and oil products and chemicals. At the same time, with the development of hydrogen economy, hydrogen fuel cells have become an important new energy application platform. To prevent poisoning of the fuel cell catalyst by a small amount of carbon monoxide (CO) in the hydrogen fuel, a water gas shift reaction may be used to purify the hydrogen fuel. As a low-temperature favorable reaction, if we can find a high-efficiency water gas shift catalyst that can work at lower temperature, we can obtain high catalytic activity while gaining thermodynamic advantages, which is also with low-temperature hydrogen fuel cells (operating temperature 70-90 degrees Celsius). The need for effective integration. Therefore, it is of great significance to develop a water gas shift catalyst with high catalytic activity and stability in the low temperature region (<150° C.).
Martin's research team cooperated with Ishikawa from Dalian University of Technology, Jose A. Rodriguez from Brookhaven National Laboratory, USA, Zhou Wu from the Chinese Academy of Sciences, the Shanxi Coal Chemistry Research Institute of the Chinese Academy of Sciences, and Wen Xiaodong from the Chinese Department of Synthetic Oils to break through the reducibility The carrier-dispersed noble metal is a traditional research idea for low-temperature shift catalysts. Using the characteristics of good thermal stability of the transition metal carbide and strong interaction with the dispersed metal, a dual-functional carbide-supported gold catalyst Au/α-MoC: cubic phase was constructed. α-MoC activates and dissociates H2O at low temperature, and the dispersed gold promotes low-temperature CO adsorption and activation, and completes the reforming reaction at the interface and generates H2. The catalyst can greatly reduce the water gas shift reaction temperature to 120 °C. At the space velocity of up to 180,000 h-1, the reaction activity reaches 1.05 molCO/(molAu*s), which is more than an order of magnitude higher than reported in the literature, and the CO conversion rate exceeds 95%, effectively solving the low temperature condition of water gas shift reaction. The problem of high reaction conversion rate and high reaction rate cannot be achieved simultaneously. The results of the EXAFS fitting of Au revealed that the Au-Au and Au-Mo bond lengths of Au loaded on α-MoC were shorter and the coordination number was lower, ie, smaller particle size than that on β-Mo2C. The interaction with α-MoC substrate is stronger. The Au-Au coordination number combined with single-atomic resolution spherical aberration correction electron microscope and theoretical simulation calculations show that under the influence of strong interaction between Au and the carrier molybdenum carbide, Au forms two-dimensional Lamellar nanostructures and the formation of electron-deficient centers are the key to the effective low-temperature activation of CO and H2O, while the catalyst exhibits excellent structural stability under high temperature activation and reaction conditions. The research work constructed a new low-temperature hydrogen production system, which provided new ideas for hydrogen economy promotion and hydrogen purification process.
The L3 edge XAFS data of Au element was obtained at the BL14W1 station of Shanghai Light Source, thus ensuring the detailed study of the electronic structure and geometry of the catalyst. The research was funded by the "973" program, the National Natural Science Foundation, the Chinese Academy of Sciences, the Youth 1000 Program, and Shanghai Light Source Key Projects.
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