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Academician Wang Enge of Peking University, Professor Jiang Ying and researcher Chen Ji cooperated with Professor Guo Jing of the school of chemistry of Beijing Normal University, and used high-resolution qplus atomic force microscope technology to capture the atomic level resolution image of protons in the water layer for the first time. It was found that hydrated protons of two configurations, Eigen and Zundel, can exist stably on the solid surface, The new configuration of hydrogen atom symmetry in surface two-dimensional ice at room temperature and atmospheric pressure caused by full quantum effect is further confirmed. The work, entitled "visualizing eigen/zundel cations and their conversion in monolayer water on metal surfaces", was published in the international top academic journal Science on July 15

in this work, researchers co deposited hydrogen atoms and water molecules on the surfaces of different metals (AU, Cu, Pt, Ru). The hydrogen atoms transferred with the metal substrate to form hydrogen ions, which further combined with water molecules to spontaneously form a two-dimensional hydrogen bond network. In order to distinguish water molecules and hydrated protons from real space, based on the detection of hydrated sodium ions in 2018 (nature 557, 701 (2018)), researchers developed a new generation of qplus type non intrusive atomic force microscope technology (qplus AFM), and improved its detection sensitivity and imaging resolution to ~2 Pico cattle and ~20 Pico meters respectively (the best level in the world), It is the first time to "see" the atomic structure of hydrated proton monomer (h3o+) and the two-dimensional hexagonal hydrogen bond network formed by the self-assembly of hydrated protons in the eigen configuration (below)

Description: AFM experimental diagram (first column hydrated ion diagram; second column hydrogen bond network diagram) and atomic structure model diagram (third column) of two-dimensional hydrogen bond network formed by self-assembly of eigen (a) and Zundel (b) configuration hydrated protons on Au (111) surface. In the model diagram, blue represents eigen/zundel configuration ions, and red represents water molecules

by increasing the concentration of hydrogen ion doping, the eigen configuration hydrated protons will be transformed into the Zundel configuration hydrated protons (Fig. 2b). The high-resolution AFM image of the hydrated proton in the Zundel configuration can directly distinguish that the proton is shared by two water molecules, forming a symmetric hydrogen bond configuration. The results of first principles path integral molecular dynamics simulation (PIMD) show that the nuclear quantum effect induces the quantum delocalization of hydrogen nuclei, which promotes the formation of symmetric hydrogen bonds, and makes the Zundel configuration stable at room temperature. This is also the first time that the microstructure of hydrated protons has been observed in real space since the concept of hydrated protons was put forward for more than 100 years, and a new two-dimensional ice state with hydrogen atom symmetry configuration has been found at room temperature

on this basis, the researchers manipulated the proton transfer through the AFM tip and found that two eigen configuration hydrated protons can be combined into a Zundel configuration hydrated proton, and the remaining proton is transferred from the water layer to the solid surface (h*), forming a zundel+h* configuration (below). This is a new proton synergistic transfer process, which goes beyond the known basic steps of hydrogen evolution reaction on the electrode surface. Further study found that there was a concentration dependent eigen Zundel transition of hydrated protons on the surface of Au (111), while hydrated protons with different concentrations on the surface of Pt (111) preferred to form a Zundel configuration (Fig. 3D). This means that when the concentration of hydrated protons is low, the hydrated protons of Zundel configuration in the water layer on the surface of Pt (111) and the h* adsorbed on the solid surface mainly produce H2 through the Heyrovsky reaction path (h+ + e- + h* → H2); When the concentration of hydrated protons increases, the coverage of h* adsorbed on the surface increases accordingly, thus opening a new Tafel reaction path (2h* → H2) for hydrogen production. These images show that the full quantum effect is helpful to understand the micro mechanism of high-efficiency hydrogen production of Pt electrode, and also provides a new idea to improve the efficiency of hydrogen production by improving electrode materials

Description: (A-C) experimental diagram and model schematic diagram of the mutual transformation of eigen and Zundel configurations manipulated by the tip; (D) Correlation between the concentrations of eigen and Zundel ions on the surface of Au (111) and Pt (111) at different hydrogen ion doping concentrations
2023-03-22 10:04:54