Asymmetric Transport Mechanisms of Hydronium and Hydroxide Ions in Amorphous Solid Water: Hydroxide Goes Brownian while Hydronium Hops

作者：Lee Du Hyeong; Choi Cheol Ho^*; Choi Tae Hoon; Sung Bong June; Kang Heon

来源：Journal of Physical Chemistry Letters, 2014, 5(15): 2568-2572.

DOI：10.1021/jz501235y

The diffusion of hydronium (H3O+) and hydroxide (OH-) ions is one of the most intriguing topics in aqueous chemistry. It is considered that these ions in aqueous solutions move via sequential proton transfer events, known as the Grotthuss mechanisms. Here, we present an experimental study of the diffusion and HID exchange of hydronium and hydroxide ions in amorphous solid water (ASW) at 140-180 K by using low-energy sputtering (LES) and temperature-programmed desorption (TPD) measurements. The study shows that the two species transport in ASW via fundamentally different molecular mechanisms. Whereas hydronium ions migrate via efficient proton transfer, hydroxide ions move via Brownian molecular diffusion without proton transfer. The molecular hydroxide diffusion in ASW is in stark contrast to the current view of the hydroxide diffusion mechanism in aqueous solution, which involves proton transfer.

• 出版日期2014-8-7