Electrochemical reduction of O2 in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid containing Zn2+ cations: deposition of non-polar oriented ZnO nanocrystalline films

Abstract

The influence of the Zn(2+) concentration and temperature on the electrochemical reduction of O(2) in a solution of zinc bis(trifluoromethanesulfonyl)imide (Zn(TFSI)(2)) salt in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR(14)TFSI) ionic liquid is presented. ZnO nanocrystalline films were then electrodeposited, under enhanced O(2) reduction, at temperatures in the 75-150 °C range. Their morphology, chemical composition, structural and optical properties were analyzed. In contrast to the polar-oriented ZnO usually obtained from aqueous and conventional solvent based electrolytes, nanocrystalline films oriented along non-polar directions, (11 ̅10) and (11 ̅20), were obtained from this ionic liquid electrolyte. A significant content of carbon was detected in the films, pointing to the active participation and crucial effect of pyrrolidinium cation (and/or byproducts) during the electrodeposition. The films showed semiconducting behavior with an optical gap between 3.43 and 3.53 eV as measured by optical transmittance. Their room temperature photoluminescence spectra exhibited two different bands centered at ∼3.4 and ∼2.2 eV. The intensity ratio between both bands was found to depend on the deposition temperature. This work demonstrates the great potential of ionic liquids based electrolytes for the electrodeposition of ZnO nanocrystalline thin films with innovative microstructural and optoelectronic properties.

Electrochemical Reduction of Oxygen in Aprotic Ionic Liquids Containing Metal Cations: A Case Study on the Na–O2 system

“…[37] This peculiarity might be ar esult of the interactions between the discharge product and ions from the IL, which are very likely to influencet he nucleation and growth of the discharge product in asimilarway to that observed and reported in the case of ZnO [20,39] and NiO. [37] This peculiarity might be ar esult of the interactions between the discharge product and ions from the IL, which are very likely to influencet he nucleation and growth of the discharge product in asimilarway to that observed and reported in the case of ZnO [20,39] and NiO.…”

“…[11] Aside from classical electrolytes based on cyclic and acyclic carbonates, ionic liquids (ILs) such as hydrophobic and aprotic N-butyl-N-methylpyrrolidiniumb is(trifluoromethanesulfonyl)imide (PYR14TFSI) have also been considered because of their potentially attractive physicochemical properties, [12][13][14] which make them suitable candidates for technological development based on green, safe, and sustainable chemistry. There are af ew reports about using the electrochemical reduction of O 2 in ILs containing metal cations( i.e., Zn 2 + , [20,21] Ni 2 + , [22] Ce 4 + [23] )t od eposit metal oxide films [Eqs. Several groups [16][17][18][19] have investigated this aspect and concluded that in ILs free of metal cations the generationofs uperoxides firstly and peroxides subsequently occur accordingly to Equations (1) and (2).…”

“…Several groups [16][17][18][19] have investigated this aspect and concluded that in ILs free of metal cations the generationofs uperoxides firstly and peroxides subsequently occur accordingly to Equations (1) and (2). There are af ew reports about using the electrochemical reduction of O 2 in ILs containing metal cations( i.e., Zn 2 + , [20,21] Ni 2 + , [22] Ce 4 + [23] )t od eposit metal oxide films [Eqs. (3) Metal-air batteriesa re intensively studied because of their high theoretical energy-storagec apability.H owever,t he fundamental science of electrodes, electrolytes, and reaction products still needs to be better understood.I nt his work, the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide( PYR14TFSI) was chosen to study the influence of awide range of metal cations (M n + )onthe electrochemical behavior of oxygen.…”

Effect of H2O2 concentration on electrochemical growth and properties of vertically oriented ZnO nanorods electrodeposited from chloride solutions

“…1 shows the CV scans recorded in a solution containing 5 mM of ZnCl 2 , 0.1 M of KCl and a variable concentration of H 2 O 2 (2, 5, 7, 10 and 15 mM). During forward scan, from À 0.6 V a cathodic current observed relating to the formation of the hydroxides ions as following [24]:…”

“…For the electrodeposition of ZnO, the majority of the published works used nitrate ions [17,20] or molecular oxygen as precursors in aqueous [21,22] and non-aqueous solvents [23,24]. However, few studies have been presented using hydrogen peroxide as a precursor [14,25,26].…”