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Updated: Oct 7, 2025
11:42
Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
15.6K
Trivalent ion overcharging on electrified graphene.
Amanda J Carr1, Sang Soo Lee1, Ahmet Uysal1
1Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, United States of America.
Summary
Graphene
Area of Science:
- Surface Science
- Electrochemistry
- Materials Science
Background:
- The electrical double layer (EDL) structure near graphene influences applications like capacitive deionization.
- Multivalent ions near graphene can cause nonclassical EDL behaviors, including overcharging and co-ion adsorption.
Purpose of the Study:
- To experimentally characterize the EDL structure at a graphene-aqueous interface under controlled potential.
- To investigate the adsorption and organization of yttrium ions (Y3+) near a negatively charged graphene surface.
Main Methods:
- Utilized in situ high-resolution X-ray reflectivity and resonant anomalous X-ray reflectivity (RAXR).
- Employed cyclic voltammetry to measure capacitance and compare with ion adsorption data.
Main Results:
- Observed significant Y3+ adsorption to negatively charged graphene, forming an extended ion profile with high coverage (1 Y3+ per 11.4 Ų).
- Demonstrated EDL overcharging, explained by co-adsorbed chloride ions screening excess positive charge.
- Identified a molecular-scale gap (≥5 Å) between adsorbed Y3+ and the graphene surface, attributed to water molecules and inert surface.
Conclusions:
- This study provides the first experimental description of a model graphene-aqueous system with controlled potential.
- Findings offer crucial insights into graphene-based systems for enhanced and selective ion separations.
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