Manipulating meso-scale solvent structure from Pd nanoparticle deposits in deep eutectic solvents

Hammons, Joshua A.; Besford, Quinn A.; Ilavsky, Jan; Christofferson, Andrew J.

doi:10.1063/5.0058605

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Manipulating meso-scale solvent structure from Pd nanoparticle deposits in deep eutectic solvents

Hammons, Joshua A.·Besford, Quinn A.·Ilavsky, Jan·Christofferson, Andrew J.

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Abstract

Deep Eutectic Solvents (DESs) are complex solutions that present unique challenges compared to traditional electrolytes. Unlike most electrolytes and ionic liquids, DESs have delicate hydrogen bond networks that are responsible for their highly sensitive compositional dependence on the melting point. Prior work has demonstrated unique nanoscale structure both experimentally and theoretically that brings both challenges and opportunities to their adoption in traditional electrochemical processes. In this study, we use in-situ sample-rotated ultra-small angle X-ray scattering to resolve the near-interface solvent structure after electrodepositing Pd nanoparticles onto a glassy carbon electrode in choline chloride:urea and choline chloride:ethylene glycol DESs. Our results indicate that solvent structure can be observed on the meso-scale in the choline chloride:urea and choline chloride:ethylene glycol systems. Importantly, this extended solvent structure peaks at -0.5 V (vs. Ag/AgCl) and decreases slightly with higher overpotentials during Pd electrodeposition. Experimentally, the nature of this structure is more pronounced in the ethylene glycol system, as evidenced by both the X-ray scattering as well as the electrochemical impedance spectroscopy (EIS). Here, molecular dynamics simulations and dipolar orientation analysis reveal that chloride delocalization near the Pd interface and long-range interactions between the choline and each hydrogen bond donor are very different and qualitatively consistent with the experimental data. These results show how the long-range solvent-deposit interactions can be tuned by changing the hydrogen bond donor in the DES and the applied potential.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY Deep eutectic solvents Delocalization Electrochemical impedance spectroscopy Electrochemistry Electrodeposition Electrolytes Molecular dynamics Nanoparticles Solvent effect Ultra small-angle X-ray scattering

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Hammons, Joshua A., Besford, Quinn A., Ilavsky, Jan, Christofferson, Andrew J.. 2021-08-20. Manipulating meso-scale solvent structure from Pd nanoparticle deposits in deep eutectic solvents. https://doi.org/10.1063/5.0058605

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