The nanoscale structure of electrocatalyst surfaces governs the selectivity and kinetics of reactions including CO(2) electroreduction (CO(2)R). Yet, their evolution under reaction conditions remains elusive, and the roles of surface hydroxyls (OHad) and the interfacial microenvironment in surface restructuring are poorly understood. Combining electrochemical atomic force microscopy, Raman spectroscopy, and grand canonical modeling, we reveal that OHad acts synergistically with COad to restructure copper (Cu) electrocatalysts during COR. Mixed OHad/COad coverage promotes lifting of surface atoms into metastable states, generating Cu adatoms and nanoclusters at mild cathodic potentials, which aggregate or dissolve at more negative potentials. This restructuring into low-coordinated Cu sites is accompanied by disordering of the interfacial water network. Nanocluster stability depends critically on CO partial pressure, while hydroxyls remain kinetically trapped on the roughened Cu surface. These findings underscore the importance of surface kinetics and interfacial microenvironments in atomic-scale surface restructuring, urging a reassessment of catalytic surface states under realistic conditions.

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The number of infected people, measured over 70-some years and across all 50 states and the District of Columbia, generally declined after vaccines were introduced.

Post Doc - Pharmacokinetic Profile Prediction

Postdoctoral Associate: aircraft-based measurements of atmospheric ammonia Join our team! The atmospheric chemistry group at the University of Minnesota (UMN) seeks applications for a Postdoctoral A...

This work investigates the role of ionic liquid (IL) ion (a)symmetry in promoting ordered structures within liquid films by studying a series of six alkylimidazolium cation isomers of varying symmetry paired with a bis(trifluoromethylsulfonyl)imide anion. The cation symmetry is varied by systematic variations in the alkyl tail lengths on either side of the imidazolium ring. IL films are extruded on a silver substrate using an in situ dynamic wetting apparatus and allowed to thin under shearing force due to gravity. Film thicknesses are monitored via spectroscopic ellipsometry. Infrared reflection absorption spectroscopy (IRRAS) with p-polarized light is used to analyze changes in dipole moments with vector components perpendicular to the substrate and thus report changes to molecular orientations and local chemical environments. Multiple vibrational modes are monitored at varying film thicknesses to deliver chemical insight into the evolving net molecular orientation within the IL films. Specifically, average molecular orientations are tracked by monitoring intensity and energy shifts of vibrational modes, including the S–N–S νas (∼1054 cm–1), SO2 νss (∼1137 cm–1), and SO2 νas (∼1330 cm–1) stretches. This provides a unique ability to determine the extent of ordering in the film. As IRRAS probes the entire film, when changes to the spectral profile cease and only a uniform decrease in absorbance is observed, only the ordered domains of the film remain on the substrate; thus, the film’s thickness is equal to the extent of ordering in the film. Ultimately, for the six alkylimidazolium IL isomers examined here, the extent of molecular ordering in the films increases with increasing asymmetry of the cation. IL ordered domains extend to 0.4 ± 0.2 μm for the most symmetric systems and to 0.7 ± 0.2 μm for the most asymmetric systems.