Juan José PARAJÓ1,2, Pablo VALLET1, Josefa SALGADO1, María VILLANUEVA1, Antía SANTIAGO1, Luis Miguel VARELA1, Carlos Manuel PEREIRA 2, Ana Teresa BRANDAO2, Antonio Fernando SILVA2, Renata COSTA2
1University of Santiago de Compostela, Santiago de Compostela, Spain
2University of Porto, O Porto, Portugal
Binary mixtures of ionic liquids and inorganic salts present electrochemical interest due to their potential as highly conductive electrolytes in electrochemical storage devices. A systematic prediction of the salt effect on the electrolyte-electrode interfacial structure of the electrical double layer (EDL) is needed to ensure the most promising electrolyte mixture formulation. For this purpose, the EDL of pure ethylammonium nitrate (EAN) and the respective mixtures with lithium nitrate (LiNO3) salt was assessed at different molality concentrations. Differential capacitance, potential of zero charge and charge density curves were obtained at the Hg/EAN interface. This allowed to propose a valid EDL structure using a mercury (Hg) as metal model for the pure EAN ionic liquid, which will be the basis to better understand the contribution/absorbability of the ions of the inorganic salt in shaping the electrolyte binary mixture at charged surfaces. The EDL model selected to describe the interfacial properties of the EAN IL adjacent layer to the electrode was the Helmholtz model, that although very simple and crude, the EDL thickness estimated from the model was validated independently. Accordingly, the method adopted is expected to be suitable in pursuing a better understanding about the role of the inorganic salt mixed with the IL at electrified interfaces.
Acknowledgements: Authors acknowledge M. Gómez (RIAIDT-USC) for the technical supporting DSC measurements. This work was supported by Spanish Ministry of Economy and Competitiveness and FEDER Program through the projects MAT2017-89239-C2-1-Pand MAT2017-89239-C2-2-P and the SISE Network RED2018-102679-Tas well as by Xunta de Galicia through GRC ED431C 2020/001 project and the Galician Network of Ionic Liquids (ReGaLIs) ED431D 2017/06.P. Vallet and J. J. Parajó thank funding support of FPI Program from Spanish Ministry of Science, Education and Universities and I2C postdoctoral Program of Xunta de Galicia, respectively. This work was financially supported by the FCT under Research Grant UIDB/00081/2020– CIQUP, LA/P/0056/2020 (IMS). Renata Costa thank FCT for funding through program DL 57/2016–Norma transitória (SFRH/BPD/89752/2012). Ana Brandão thanks the Ph.D. grant awarded by FCT with reference 2021.04783.
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