Interaction of SO2 and H2O with the Platinum (001), (011),and (111) Surfaces: A DFT Study.

Given the importance of SO2 as a pollutant species in the environment and its role in the hybrid sulphur (HyS) cycle for hydrogen production, we carried out a density functional theory study of its interaction with the Pt (001), (011), and (111) surfaces. First, we investigated the adsorption of a single SO2 molecule on the three Pt surfaces. On both the (001) and (111) surfaces, the SO2 had a S,O-bonded geometry, while on the (011) surface, it had a co-pyramidal and bridge geometry.


The largest adsorption energy was obtained on the (001) surface (Eads = -2.47 eV), followed by the (011) surface (Eads = -2.39 and -2.28 eV for co-pyramidal and bridge geometries, respectively) and the (111) surface (Eads = -1.85 eV). When the surface coverage was increased up to a monolayer, we noted an increase of Eads/SO2 for all the surfaces, but the (001) surface remained the most favourable overall for SO2 adsorption. On the (111) surface, we found that when the surface coverage was θ > 0.78, two neighbouring SO2 molecules reacted to form SO and SO3. Considering the experimental conditions, we observed that the highest coverage in terms of the number of SO2 molecules per metal surface area was (111) > (001) > (011).


During the adsorption of a single H2O molecule on various Pt surfaces, it was found that the lowest Eads was obtained for the dissociative adsorption of H2O on the (001) surface, followed by the (011) and (111) surfaces. When the surface coverage was increased up to a monolayer, we noted an increase in Eads/H2O with increasing coverage for the (001) surface, while for the (011) and (111) surfaces, Eads/H2O decreased. Considering experimental conditions, we observed that the highest coverage was obtained on the (011) surface, followed by the (111) and (001) surfaces.

Dr. Marietjie Ungerer, Visiting Researcher, (Cardiff)

Biography

I completed my undergraduate studies at the North-West University in 2010 and was awarded the best BSc Honors student in Chemistry. In 2011 I enrolled for a Masters study in Chemistry within the Membrane Technology Group of the Research Focus Area: Chemical Resource Beneficiation at the North-West University. During this study, I focused on the separation of two transition metals, tantalum and niobium, with solvent extraction in conjunction with industry. In November 2017 I submitted my Ph.D. thesis on the molecular modelling of species pertaining to the solvent extraction of tantalum penta-fluorides. During this study, the DFT-based modelling and molecular dynamics simulations to model not only various Ta species in both a water and acid environment, but also to simulate these species and interactions at a water-organic phase interface. During the last six months of my PhD is also had the opportunity to visit and collaborate at Cardiff University, with the support of a Newton funded exchange program. During this time, I collaborated with Prof. Nora de Leeuw’s group where we investigated the interaction of both water and sulphur dioxide on various platinum surfaces, utilising Linux-based Ab initio software. 

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