(521ak) Impact of Electrolytes on the Adsorption of Phenol on a Platinum Electrode

Electrocatalytic reactions of organic molecules can be influenced by electrolyte composition through competitive adsorption and structural changes in the interfacial water layer. Competitive adsorption lowers surface coverage of reactants and intermediates, and thus decreases electrocatalytic rates. However, the effect of electrolyte on interfacial water layer and how it affects adsorption of organics is less understood. Herein, we report the effects of cations and anions in electrolytes on the adsorption strength of phenol on polycrystalline platinum (Pt). We focus on ions that do not specifically adsorb to Pt to elucidate how non-specific adsorption of ions and structural changes to the interfacial water layer affect phenol adsorption. We use atomistic modeling to predict the adsorption free energy of anions (ClO₄^-, NO₃^-, and CH₃COO^‑) and cations (Li⁺, Na⁺, and Cs⁺) on Pt(111) as a function of applied electrochemical potential. We determine a potential range in which ions do not adsorb in the hydrogen underpotential deposition (H_upd) region of Pt where we experimentally study phenol adsorption strength. We predict that none of the considered cations adsorb on Pt(111) in the H_upd region. Further, we predict that ClO₄^- and NO₃^- do not readily adsorb on Pt(111), consistent with previous work in the field,¹ while CH₃COO^‑ adsorbs on Pt(111). We model the adsorption energy of phenol in the presence of ions using molecular dynamics simulations and validate our model against cyclic voltammetry experiments. A comprehensive understanding of the impact of electrolytes on the aqueous-phase adsorption of phenol on Pt will improve our understanding of phenol hydrogenation and oxidation, which is relevant to bio-oil production and organic pollution abatement.

References:

(1) Kamat, G. A.; Zamora Zeledón, J. A.; Gunasooriya, G. T. K. K.; Dull, S. M.; Perryman, J. T.; Nørskov, J. K.; Stevens, M. B.; Jaramillo, T. F. Commun Chem 2022.