Trends in the Adsorption and Dissociation of Water Clusters on Flat and Stepped Metallic Surfaces

Abstract

Understanding the structure and chemical reactivity of water adsorbed at metallic surfaces is very important in many processes such as catalysis, corrosion, and electrochemistry. Using density functional theory calculations, we investigate the adsorption and dissociation of water clusters on flat and stepped surfaces of several transition metals: Rh, Ir, Pd, and Pt. We find that water binds preferentially to the step edges than to terrace sites, thus linear clusters or one-dimensional water wires can be isolated by differential desorption. The clusters formed at the step are stabilized by the cooperative effect of chemical bonds with the metal and hydrogen bonding. The enhanced reactivity of the step edges and the cooperative effect of hydrogen bonding improve the chances of partial dissociation of water clusters. We assess the correlations between adsorption and dissociation energies, observing that they are increased on stepped surfaces. We present a detailed interpretation of water dissociation by analyzing changes in the electronic structure of both water and metals. The identification of trends in the energetics of water dissociation at transition metals is expected to aid the design of better materials for catalysis and fuel cells, where the density of steps at surfaces would be a relevant additional parameter

Adsorption and Activation of Water on Cuboctahedral Rhodium and Platinum Nanoparticles

“…11 The (211) and (221) stepped surfaces, mimicking the edges of realistic nanoparticles, have been found to be more reactive towards water, which is likely due to the lower coordination of the surface sites. 10,11 These findings are in line with the computational reports by Calle-Vallejo et al…”

“…The adsorption energies on the extended surface models indicate that water favors the E site on the stepped (211) surfaces over the terrace sites on the (111) and (100) surfaces in line with the previous computational reports. [9][10][11][12][13][14][15][16][17][18] The 7 Overall, the highly undercoordinated C sites of the nanoparticles bind water the strongest, as intuitively expected, followed by the E, 100T, and 111T sites in the same order as for the extended surface models.…”

“…[9][10][11][12][13][14][15][16][17][18] Calculation reports have been primarily focused on representing metal surfaces with flat and stepped surface slabs to mimic different structural features of realistic nanoparticles at relatively low computational expenses. The flat (111) and (100) surfaces of Rh and Pt have been shown to adsorb and activate water equally well.…”

Double-Stranded Water on Stepped Platinum Surfaces

“…Theoretical studies indicated that surface defects, e.g. steps, cause significant disruptions of extended water frameworks [13][14][15][16][17].…”

“…The exact nature of the adsorption structure was not resolved. In recent years, multiple theoretical studies have addressed water adsorption and solvation along platinum step edges [13][14][15]22]. In these studies, water was found to form one-dimensional (1D) lines along the step edge.…”