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Effect of Step Density and Orientation on the Apparent pH Dependence of Hydrogen and Hydroxide Adsorption on Stepped Platinum Surfaces

Published

Author(s)

Ian McCrum, Xiaoting Chen, Kathleen A. Schwarz, Michael Janik, Marc Koper

Abstract

The detailed atom-level structure of platinum surfaces is of immense importance to electrocatalytic reactions in which surface-bonded intermediates (hydrogen and hydroxyl) play a crucial role, especially for fuel cells and hydrogen production. Here, with the support of a combination of computational and experimental results, the alkali metal cation (Li+, Na+, K+, and Cs+) effect on the non-Nernstian pH shift of the Pt(554) and Pt(533) step associated voltammetric peak is elucidated over a wide pH window (1 to 13). When the result is correlated with a previously reported study on Pt(553), the non-Nernstian pH shift of the step induced peak is concluded to be independent of the step density and the step orientation. Further, our density functional theory (DFT) study shows that, similar to our previous work on Pt(553), the pH dependence of the peak associated with the 100-type step of the Pt(533) surface is caused by the adsorption of an alkali metal cation near the step edge and its subsequent weakening of hydroxide adsorption. The DFT results well capture the effect of alkali metal cation identity and alkali cation coverage, in the sense that increasing electrolyte pH and cation concentration lead to increased cation coverage, and a greater weakening effect on hydroxide adsorption.
Citation
Journal of Physical Chemistry C

Citation

McCrum, I. , Chen, X. , Schwarz, K. , Janik, M. and Koper, M. (2018), Effect of Step Density and Orientation on the Apparent pH Dependence of Hydrogen and Hydroxide Adsorption on Stepped Platinum Surfaces, Journal of Physical Chemistry C, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=925602 (Accessed April 19, 2021)
Created July 3, 2018, Updated February 7, 2020