Crystallization kinetics of thin water films on Pt(111): effects of oxygen and carbon-monoxide adspecies.

Ryutaro Souda,Takashi Aizawa

doi:10.1039/c8cp06438e

Abstract

This paper describes nucleation, epitaxial growth, and wettability of water on Pt(111) and how they are influenced by oxygen and carbon-monoxide adspecies, based on reflection high energy electron diffraction (RHEED), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and temperature-programmed desorption (TPD). Amorphous solid water deposited onto the pristine Pt(111) substrate crystallizes into ice Ih together with a 2D layer at 150 K, whereas ice Ic (stacking disordered ice or a mixture of ice Ic and Ih) is formed preferentially onto oxygenated Pt(111) (CO-adsorbed Pt(111)) at 155-160 K (150 K). The ice nucleation and epitaxial growth tend to be hampered on the oxygenated Pt(111) surface via hydrogen bond formation with chemisorbed oxygen. The CO-adsorbed Pt(111) surface is hydrophobic, as evidenced by the fact that water forms a complex with CO during evaporation of crystallites at 160-165 K. A disordered 2D layer remains on pristine Pt(111) up to 175 K, whereas an ordered 2D layer exhibiting the (√3 ×√3)R30° structure formed on oxygenated Pt(111) up to 200 K.

Highlights

Interfacial water is ubiquitous in nature and plays an important role in fundamental research and technological applications
How the water molecules in the monolayer regime interact with oxygen and carbon-monoxide adspecies on Pt(111) was investigated in comparison with the results using the pristine Pt(111) substrate in terms of the crystallization kinetics and surface wettability
The amorphous solid water (ASW) film on the Pt(111) surface crystallizes above 155–160 K (150 K), thereby forming epitaxially-grown ice Ih grains and a disordered 2D layer

Summary

Introduction

Interfacial water is ubiquitous in nature and plays an important role in fundamental research and technological applications. Interactions of water with solid surfaces have been studied extensively at cryogenic temperatures in terms of wettability, chemical reaction, crystallization kinetics, etc.[1,2] A considerable attention has been focused on water monolayers formed on close packed transition metal substrates because their lateral lattice parameter matches well with that of crystalline ices. In contrast to the conventional picture, it was depicted based on X-ray absorption measurements that all water molecules in the first layer bind directly to the Pt(111) surface via alternating metal–oxygen and metal–hydrogen bonds, thereby forming a flat H-down water monolayer.[3] It was revealed using helium atom scattering (HAS)[4] and LEED5 that ordered 2D domains exhibiting (O37 Â O37)R251 and (O39 Â O39)R161 structures formed via a slow deposition of water molecules at a temperature of ca. It was revealed using helium atom scattering (HAS)[4] and LEED5 that ordered 2D domains exhibiting (O37 Â O37)R251 and (O39 Â O39)R161 structures formed via a slow deposition of water molecules at a temperature of ca. 130 K;

Results

Discussion

Conclusion