title: A comparative AFM study of the interfacial nanostructure in imidazolium or pyrrolidinium ionic liquid electrolytes for zinc electrochemical systems.
abstract: The electrochemical systems containing zinc dicyanamide salt (Zn(dca)2) in both 1-ethyl-3-methylimidazolium dicyanamide ([C2mim][dca]) and N-butyl-N-methylpyrrolidinium dicyanamide ([C4mpyr][dca]) ionic liquids (ILs) have been studied by atomic force microscopy (AFM) on a highly oriented pyrolytic graphite (HOPG) surface under different conditions and applied potentials. The results reveal the following: (1) interfacial layers exist in both ILs, even after the addition of 3 wt% water and 9 mol% Zn(dca)2salt. (2) The number of layers is different for the different ILs, with the [C2mim][dca]-based samples exhibiting a much more limited interfacial structure compared to the [C4mpyr][dca] at almost all of the tested conditions. (3) For the [C4mpyr][dca]-based samples, without added zinc salt, the number of detected interfacial layers increases with negative potential. With added zinc, the [C4mpyr][dca] sample shows about the same number of layers independent of the applied potentials, namely between 5-7. Likewise, for the [C2mim][dca] samples, with the zinc added the sample shows the same number of layers at the applied potentials, but for this system only 1-2 layers are detected. And (4) the addition of Zn(dca)2into the [C2mim][dca] IL does not cause a large change in the interfacial ordering, whereas the addition of the same salt into the [C4mpyr][dca] samples is marked by a stark increase in both the number and the consistency of the perceived interfacial layers. These results are significant because they show a marked difference in the interfacial nanostructure between two zinc-based electrochemical systems that were previously shown to have distinctly different electrochemical behaviour, despite their chemical similarity.
authors.affiliation: ARC Centre of Excellence for Electromaterials Science (ACES), Institute for Frontier Materials (IFM), Deakin University Burwood Campus, 221 Burwood Hwy, Burwood, VIC 3125, Australia. patrick.howlett@deakin.edu.au.
authors.forename: Srđan
authors.identifier: http://orcid.org/0000-0002-9008-9330
authors.initials: S
authors.lastname: Begić
authors.affiliation: Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.affiliation: Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Rob
authors.initials: R
authors.lastname: Atkin
authors.affiliation: CSIRO, Gate 1, Bayview Ave, Clayton, VIC 3168, Australia.
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Hollenkamp
authors.affiliation: ARC Centre of Excellence for Electromaterials Science (ACES), Institute for Frontier Materials (IFM), Deakin University Burwood Campus, 221 Burwood Hwy, Burwood, VIC 3125, Australia. patrick.howlett@deakin.edu.au.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Howlett