(532ar) Aqueous-Phase Heats of Adsorption of Phenolics in Mixed Electrolytes

Anthropogenic activities add significant amounts of phenolic pollutants to water systems. Electrocatalytic oxidation driven by renewable energy can oxidize these organics from wastewater, but improved electrocatalysts are needed. To guide electrocatalyst development it is critical to understand the adsorption thermodynamics of phenolics in aqueous electrolytes as it determines the coverage of organics and alters activation barriers. We study mixed electrolyte systems using different chaotropic and kosmotropic agents to analyze the role of solvent composition on aqueous-phase heats of adsorption, which we hypothesize will greatly affect the phenolic adsorption energies by changing the stability of water’s hydrogen-bonding network at the solvent/electrode interface. We report density functional theory (DFT) calculated and experimentally measured aqueous-phase heats of adsorption of phenolics on Pt(111) in mixed electrolytes systems (e.g., acetic acidic/water). We consider the following phenolics: phenol, p-cresol, catechol, and guaiacol. We show that traditionally used implicit solvent model calculations overpredict the heats of adsorption for aqueous systems by ∼100 kJ mol^-1 compared to our experimental measurements. We use a bond-additivity model^1,2 based on DFT calculations to account for solvation of phenolics and displacement of solvent molecules from the metal surface to more accurately predict the aqueous-phase heats of adsorption. We compare our bond-additivity model predictions with experimental measurements and show promising agreement. This on-going study will provide detailed understanding of the effect of co-solvent on aqueous-phase adsorption of phenolics to surfaces and will guide future studies to link phenolic adsorption to electrocatalytic oxidation kinetics.

References:

1. Nirala Singh and Charles T. Campbell. ACS Catalysis2019 9 (9), 8116-8127
2. James Akinola, Charles T. Campbell, and Nirala Singh. The Journal of Physical Chemistry C2021 125 (44), 24371-24380