NCAFM2023 Programme Booklet

Tuesday 1120 - 1140

VISUALIZING EIGEN ZUNDEL CATIONS AND THEIR INTERCONVERSION IN MONOLAYER WATER ON METAL SURFACES

Ye Tian (Presenting) 1 , Jiani Hong 1 , Duanyun Cao 1 , Sifan You 1 , Yizhi Song 1 , Jing Guo 2 , Ji Chen 1 , En-Ge Wang 1 , Ying Jiang 1

1 International Center for Quantum Materials, Peking University, 100871 China 2 College of Chemistry, Beijing Normal University, 100875 China

Email: tianye420@pku.edu.cn

Hydrated protons are ubiquitous in solutions and involved in a variety of physical, chemical, biological, and energy-related processes. (1, 2) However, imaging and identifying the configuration of Zundel and Eigen cations and hydrated protons within the H bonding network of water remain a great challenge because of the high similarity between the hydronium (H 3 O + ) and the water molecule (H 2 O). Recently, we performed the coadsorption of deuterium (D) atoms and D 2 O molecules on different metal substrates (Au, Cu, Pt, Ru), where the ionized D+ and D 2 O molecules can self-assemble into a two-dimensional (2D) hydronium-water overlayer. (3) We have substantially improved the resolution and sensitivity of the qPlus-AFM, such that the configuration of Zundel and Eigen cations solvated in the 2D water network could be directly visualized with an atomic-level resolution. Furthermore, we conducted the tip manipulation experiments to explore the dynamics of hydronium ions at the interface and found a new proton transfer pathway, accompanied with a simultaneous proton transfer from the water layer to the substrate, which is beyond the previously known elementary steps of hydrogen evolution reaction (HER). In addition, the stabilization of the 2D Zundel-water layer with long-range order may also open up a new possibility of exploring novel physical properties related to symmetric H bonds in the absence of high pressure.

Fig. 1 High-resolution AFM images and atomic structures of self-assembled Eigen (A)/Zundel (B) water monolayer on Au(111) surface.

References [1] D. Marx, M. E. Tuckerman, J. Hutter, M. Parrinello, Nature 1999, 397: 601–604. [2] Agmon et al., Chem. Rev. 2016, 116: 7642–7672. [3] Tian Y, Hong J, Cao D, et al., Science 2022, 377: 315–319.

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