Nitrate protic ionic liquids as electrolytes: Towards hydrogen sorption in Pd

The process of hydrogen electrosorption in the Pd thin film electrode was examined in three nitrate ionic liquids (ILs): ethylammonium nitrate (EAN), propylammonium nitrate (PAN) and 1-ethylimidazolium nitrate (C2IMN). The Pd electrode was obtained by electrodeposition on a golden matrix from palladium chloride solution. Cyclic voltammetry, chronoamperometry and chronopotentiometry were used for the electrochemical analysis. The hydrogen capacity (H/Pd) of Pd electrodes subjected to various pretreatment procedures was determined using cyclic voltammetry. The max. H/Pd equals to 0.6-0.7. In case of C2IMN IL, the noticeable phenomenon of a significant Pd dissolution under the open circuit conditions and during electrochemical hydrogen sorption experiment was observed. The physico-chemical properties such as density, ionic conductivity, dynamic viscosity and water content before and after electrochemical measurements were designated. The nitrate ionic liquid stability under the electrochemical measurement conditions was confirmed by the means of Raman and H-1 NMR spectroscopies. H-1 NMR spectroscopy also served as a tool to compare the acidity of nitrate ILs: C2IMN>PAN>EAN. (C) 2019 Elsevier Ltd. All rights reserved.