Hydrogen-Bond Dynamics of Water at the Interface with InP/GaP(001) and the Implications for Photoelectrochemistry

Abstract

We investigate the structure, topology, and dynamics of liquid water at the interface with natively hydroxylated (001) surfaces of InP and GaP photoelectrodes. Using ab initio molecular dynamics simulations, we show that contact with the semiconductor surface enhances the water hydrogen-bond strength at the interface. This leads to the formation of an ice-like structure, within which dynamically driven water dissociation and local proton hopping are amplified. Nevertheless, the structurally similar and isovalent InP and GaP surfaces generate qualitatively different interfacial water dynamics. This can be traced to slightly more covalent-like character in the binding of surface adsorbates to GaP, which results in a more rigid hydrogen-bond network that limits the explored topological phase space. As a consequence, local proton hopping can give rise to long-range surface proton transport on InP, whereas the process is kinetically limited on GaP. This allows for spatial separation of individual stages of hydrogen-evolving, multistep reactions on InP(001). Possible implications for the mechanisms of cathodic water splitting and photocorrosion on the two surfaces are considered in light of available experimental evidence.

Distinct and dramatic water dissociation on GaP(111) tracked by near-ambient pressure X-ray photoelectron spectroscopy

“…[1][2][3][4][5][6] Such devices are of particular interest, because solar energy can be converted to chemical energy and stored in the form of hydrogen, a promising candidate for sustainable and clean fuels in the future. [1][2][3][4][5][6] Such devices are of particular interest, because solar energy can be converted to chemical energy and stored in the form of hydrogen, a promising candidate for sustainable and clean fuels in the future.…”

“…[14][15][16] In contemporary technology, the most efficient PEC devices comprise III-V semiconductor photoelectrodes, [17][18][19][20][21][22][23] which are typically phosphide-based. 4,6 Hydrogen-networking and hydrogen transfer are the fundamental processes to be addressed in order to understand and characterize semiconductor surfaces that are exposed to a water environment. Since PEC processes occur in an aqueous environment, it is essential to understand the nature of water interactions with semiconductors and the possible oxidation and reduction mechanisms at the H 2 O/semiconductor interface.…”

“…Since PEC processes occur in an aqueous environment, it is essential to understand the nature of water interactions with semiconductors and the possible oxidation and reduction mechanisms at the H 2 O/semiconductor interface. 4,15 Using first-principles density functional theory (DFT) calculations, Munoz-Garcia et al reported the presence of hydride-like H atoms on the GaP(110) surface as a result of water dissociation via hydrogenbonded intermediates. 25,26 Therefore, much effort has been made to explore hydrogen-bond networks at the water/semiconductor interface.…”

“…4,15,16,27 Water, in its molecular form, and water dissociation products can greatly influence the chemical and electrical structures of semiconductor surfaces. 4,15,16,27 Water, in its molecular form, and water dissociation products can greatly influence the chemical and electrical structures of semiconductor surfaces.…”

Methods of photoelectrode characterization with high spatial and temporal resolution

“…Nevertheless, several groups have adopted AIMD approaches to study the structure and chemistry of semiconductor-water interfaces for PEC applications. 198,201,[213][214][215][216][217][218][219][220][221][222][223][224][225] The presence of semiconductor surfaces often significantly alters the dynamical and chemical properties of water; conversely, the presence of the electrolyte can significantly alter the physiochemical properties of the semiconductor. Accordingly, recent simulations have reported a wide variety of complex chemical processes active at semiconductor surfaces when liquid water is included explicitly, such as water dissociative adsorption, 198,201,214,[216][217][218]221,222,224 surface hydroxylation and radical formation, 198,201,214,[216][217][218][219]221,223 unusual changes in the hydrogen-bond network, 198,201,[213][214][215][216][217][218][219][220] and fast sur...…”