Water plays a crucial role in a variety of heterogeneous catalytic reactions, but how it participates in the atomic-scale characterization of these chemical processes is a major challenge. Based on this,Professor Guo Jing of Beijing Normal University, Associate Researcher Cao Duanyun of Beijing Institute of Technology, and Assistant Professor Guo Qing of Southern University of Science and Technology, etcIn this paper, the effect of interfacial water on the deprotonation of formic acid (FA) on metal surfaces was directly observed by scanning tunneling microscopy and Qplus-based non-contact atomic force microscopy. Fa dissociates when it is co-adsorbed with water on the surface of Cu(111) to form hydronium hydrate ions and formic acid ions. Most hydrated protons and formic acid ions exhibit phase separation behavior on Cu(111), in which the Eigen and Zundel cations aggregate into a monolayer of hexagonal hydrogen bond (H bond) network, and the didentate formic acid ion is solvated with water and aggregated into a 1D chain or 2D H bond network.
VASP Interpretation
Through DFT calculations and AFM characterization, the authors captured some metastable structures of the Fa and water complexes at the interface between the hydronium hydride ions and formic acid phases on Cu(111), thus reconstructing the proton transfer pathway during deprotonation. First, the Fa and water molecules are assembled into a hexagonal hydrogen bond network, in which the O-C-O bond backbone of the flattened Fa molecule is resolved in the AFM image. Acid protons are transferred from FA to nearby water molecules, forming contact ion pairs of formate and hydronium hydrate ions (HCOO·H3O+).
In addition, the excess protons can be further transferred within the water-hydrogen bond network, resulting in the separation of formic acid and hydronium ion pairs, resulting in stable eigen-type hydrated protons. The authors calculated the deprotonation process of Fa in Fa-water complexes on Cu(111) and calculated the climbing image nudge elastic band (CNEB), and the significant reduction of the energy barrier indicates that the interfacial water has a promoting effect on the deprotonation of Fa and is an efficient catalyst for OH bond cleavage. DFT calculations show that the process is carried out in the water-Fa complex through the Grotthuss proton transfer mechanism, that is, the acid protons are transferred from the Fa to nearby water, and further transferred in the H-bonded water network to form formic acid ions and hydronium hydrate ions.
visualizing the promoting role of interfacial water in the deprotonation of formic acid on cu(111). j. am. chem. soc.,, doi: ht-tps: