化学
氢铵
脱质子化
格式化
溶剂化
离解(化学)
无机化学
甲酸
解吸
齿合度
氢氧化物
氢键
光化学
结晶学
催化作用
物理化学
分子
离子
吸附
有机化学
晶体结构
作者
Pu Yang,Honggang Liu,Qingwei Jin,Yuemiao Lai,Yi Zeng,Chen Zhang,Jia Dong,Wenyu Sun,Qing Guo,Duanyun Cao,Jing Guo
摘要
Water plays a crucial role in various heterogeneous catalytic reactions, but the atomic-scale characterization of how water participates in these chemical processes remains a significant challenge. Here we directly visualize the promoting role of interfacial water in the deprotonation of formic acid (FA) on a metal surface, using combined scanning tunneling microscopy and qPlus-based noncontact atomic force microscopy. We find the dissociation of FA when coadsorbed with water on the Cu(111) surface, resulting in the formation of hydronium and formate ions. Interestingly, most of the hydrated proton and formate ions exhibit a phase-separated behavior on Cu(111), in which Eigen and Zundel cations assemble into a monolayer hexagonal hydrogen-bonding (H-bonding) network, and bidentate formate ions are solvated with water and aggregate into one-dimensional chains or two-dimensional H-bonding networks. This phase-separated behavior is essential for preventing the proton transfer back from hydronium to formate and the reformation of FA. Density functional theory calculations reveal that the participation of water significantly reduces the deprotonation barrier of FA on Cu(111), in which water catalyzes the decomposition of FA through the Grotthuss proton transfer mechanism. In addition, the separate solvation of hydronium and bidentate formate ions is energetically preferred due to the enhanced interaction with the copper substrate. The promoting role of water in the deprotonation of FA is further confirmed by the temperature-programmed desorption experiment, which shows that the intensity of the H2 desorption peak significantly increases and the desorption of FA declines when water and FA coadsorbed on the Cu(111) surface.
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