Structural characterization of water-metal interfaces

Abstract

We analyze and compare the structural, dynamical, and electronic properties of liquid water next to prototypical metals including Pt, graphite, and graphene. Our results are built on BornOppenheimer molecular dynamics (BOMD) generated using density functional theory (DFT) which explicitly include van der Waals (vdW) interactions within a first principles approach. All calculations reported use large simulation cells, allowing for an accurate treatment of the water-electrode interfaces. We have included vdW interactions through the use of the optB86b-vdW exchange correlation functional. Comparisons with the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional are also shown. We find an initial peak, due to chemisorption, in the density profile of the liquid water-Pt interface not seen in the liquid water-graphite interface, liquid water-graphene interface, nor interfaces studied previously. To further investigate this chemisorption peak, we also report differences in the electronic structure of single water molecules on both Pt and graphite surfaces. We find that a covalent bond forms between the single water molecule and the Pt surface, but not between the single water molecule and the graphite surface. We also discuss the effects that defects and dopants in the graphite and graphene surfaces have on the structure and dynamics of liquid water.

OH formation and H2adsorption at the liquid water–Pt(111) interface

“…The area under the two O density peaks corresponds to an average coverage of 0.16 ML from the surface bound water and 0.59 ML from the second layer water (one molecule per surface Pt is equal to 1 ML). The observation of low surface coverage and larger second layer coverage is in agreement with other AIMD simulations of water on Pt(111), 20 , 22 but different from certain MD simulations based on inter-atomic potentials, which predict close to 1 ML coverage of surface bound water molecules. 40 Importantly, it also differs from the traditional static water bilayer model, which consists of 1/3 ML surface bound water molecules and 1/3 ML water molecules with H pointing towards the surface.…”

“…Ab initio molecular dynamics (AIMD) captures the dynamics of liquid water and is the method of choice to study liquid water–metal interfaces. 18 – 22 …”

Advanced Materials for Energy-Water Systems: The Central Role of Water/Solid Interfaces in Adsorption, Reactivity, and Transport

“…The design and optimization of electrochemically reactive interfaces are among the open challenges in developing sustainable, advanced materials that handle, process, and treat water. ,− Theoretical models and computational studies play an important role in overcoming these challenges by providing predictions of optimal materials interfaced with water to be used in, for example, water treatment devices and purification membranes. − At the same time, they are a necessary component to elucidate many aspects of experimental investigations and help guide future experimental studies, including most notably those described above. However, to date, computational screening schemes for materials properties have mostly focused on bulk properties of candidate systems, thus neglecting the structure and chemistry of surfaces and interfaces with the liquid, except in recent first-principles studies .…”