Addressing the nature and reductive stability of alkylthiol-modified Cu electrode surfaces
- 1Department of Chemistry
- 2AMPEL
- 3University of British Columbia
Abstract
Cu surfaces modified with molecular adsorbates are being used in electrocatalyic processes (e.g., CO2 reduction (CO2RR)) to improve performance, but the nature and stability of molecular adsorbates (e.g. thiols) on Cu remain poorly understood owing to the sensitivity of Cu to oxidation and the complex chemical nature of the interface. To address these challenges, alkylthiol modification of 10 monolayers of electrodeposited Cu onto single-crystal Au bead electrodes has been prepared and studied using electrochemistry and in-situ fluorescence imaging. Under rigorous O2-free and H2O-free conditions, oxide-free Cu surfaces were produced. Modification of these oxide-free surfaces with alkylthiols resulted in a Cu2S overlayer. Oxide-free Cu surfaces modified with alkylthiol in the presence of trace H2O or O2 was found to have an increased amount of Cu2S, identified by electrochemistry and ex-situ Raman. The reductive stability of the alkylthiol modified Cu surface was investigated using a fluorophore-labelled DNA-alkylthiol adsorbate and in-situ fluorescence microscopy. Oxide-free Cu surfaces modified with alkylthiols produced a surface that was slightly more reductively stable (by-0.1 to-0.2V) when compared with alkylthiol self-assembled monolayers (SAMs) on Au, but do not show the characteristics of an alkyl-thiol SAM. Under similar modification procedures but using slightly oxidized Cu surfaces, the adsorbates were not removed using reducing potentials more negative than hydrogen evolution, suggesting a multilayer adsorbate structure composed of Cu2S with non-specifically adsorbed species. Thus, Cu surfaces prepared in the presence of trace O2and H2O may have a Cu-sulfide overlayer rather than a Cu-alkylthiol monolayer, even at reducing potentials typical of CO2RR or other electrocatalysis processes. More generally, the quantitative methodology that we developed for studying Cu electrodes is a framework for gaining insight into the preparation and molecular modification of other non-noble metal electrodes of interest for electrocatalysis.
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BibTeX
@misc{baker2026addressing,
title = {{Addressing the nature and reductive stability of alkylthiol-modified Cu electrode surfaces}},
author = {Daina V. Baker and Gilberto Martinez-Blanco and W. Russ Algar and Dan Bizzotto},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009137/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009137/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Addressing the nature and reductive stability of alkylthiol-modified Cu electrode surfaces
AU - Daina V. Baker
AU - Gilberto Martinez-Blanco
AU - W. Russ Algar
AU - Dan Bizzotto
PY - 2026
DA - 2026/09/21
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009137/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009137/v1
AB - Cu surfaces modified with molecular adsorbates are being used in electrocatalyic processes (e.g., CO2 reduction (CO2RR)) to improve performance, but the nature and stability of molecular adsorbates (e.g. thiols) on Cu remain poorly understood owing to the sensitivity of Cu to oxidation and the complex chemical nature of the interface. To address these challenges, alkylthiol modification of 10 monolayers of electrodeposited Cu onto single-crystal Au bead electrodes has been prepared and studied using electrochemistry and in-situ fluorescence imaging. Under rigorous O2-free and H2O-free conditions, oxide-free Cu surfaces were produced. Modification of these oxide-free surfaces with alkylthiols resulted in a Cu2S overlayer. Oxide-free Cu surfaces modified with alkylthiol in the presence of trace H2O or O2 was found to have an increased amount of Cu2S, identified by electrochemistry and ex-situ Raman. The reductive stability of the alkylthiol modified Cu surface was investigated using a fluorophore-labelled DNA-alkylthiol adsorbate and in-situ fluorescence microscopy. Oxide-free Cu surfaces modified with alkylthiols produced a surface that was slightly more reductively stable (by-0.1 to-0.2V) when compared with alkylthiol self-assembled monolayers (SAMs) on Au, but do not show the characteristics of an alkyl-thiol SAM. Under similar modification procedures but using slightly oxidized Cu surfaces, the adsorbates were not removed using reducing potentials more negative than hydrogen evolution, suggesting a multilayer adsorbate structure composed of Cu2S with non-specifically adsorbed species. Thus, Cu surfaces prepared in the presence of trace O2and H2O may have a Cu-sulfide overlayer rather than a Cu-alkylthiol monolayer, even at reducing potentials typical of CO2RR or other electrocatalysis processes. More generally, the quantitative methodology that we developed for studying Cu electrodes is a framework for gaining insight into the preparation and molecular modification of other non-noble metal electrodes of interest for electrocatalysis.
ER -