Recently, Professor Li Jun of Tsinghua University and Associate Professor Yu Xiaohu of Shaanxi University of Science and Technology published a research paper on Science China Materials. Based on first principles, the system The geometric and electronic structures of transition metal single atoms (iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum) supported on phosphotungstic acid (PTA) catalyst were studied, and further antioxidant 168 ethylene was studied Possible reaction mechanism for epoxidation over iron single-atom catalysts. The study found that the most likely position for PTA to bind transition metal single atoms is the vacancy in the four-coordinated state. Theoretical calculations of the catalytic activity of ethylene epoxidation show that the non-noble metal Fe1-PTA has considerable adsorption energy, which is the key physical quantity that triggers this catalytic cycle. Professor Li and others further conducted bonding analysis of the combination of iron single atoms and PTA, and found that the charge was transferred from the iron single atom to the PTA cluster, and the strong Fe–O covalent metal-carrier interaction (CMSI) was responsible for its high stability. The basis of sex.
arkema Figure 1 Top and side views of the optimized structure of PTA.
The possible catalytic mechanism of ethylene epoxidation on the catalyst Fe1-PTA includes three steps: 1) Oxygen molecules are adsorbed on Fe1-PTA through charge transfer Above; 2) The first ethylene molecule attacks the oxygen molecule adsorbed on Fe1-PTA, and subsequently forms C2H4O; 3) The oxygen atoms adsorbed on the surface and The second ethylene molecule generates C2H4O, completing the catalytic cycle. This study found that the epoxidation of ethylene by Fe1-PTA mainly proceeds through the Eley-Rideal mechanism.
Figure 2 Initial state (IS) and transition state (TS) of ethylene epoxidation on Fe1-PTA and optimized geometry of the final state (FS).
This work provides a theoretical basis for the development of efficient heterogeneous non-noble metal single-atom ethylene epoxidation catalysts.
The research results were recently published in Science China Materials, 2020, 10.1007/s40843-020-1399-y.
