Influence of Chloride and Nitrate Anions on Copper Electrodeposition onto Au(111) from Deep Eutectic Solvents

Abstract

Copper electrodeposition on Au(111) from deep eutectic solvents (DESs) type III was investigated employing cyclic voltammetry as well as chronoamperometry. It was further examined on Au(poly) using the electrochemical quartz crystal microbalance (EQCM). The employed DESs are mixtures of choline chloride (ChCl) or choline nitrate (ChNO3) with ethylene glycol (EG) as hydrogen bond donor (HBD), each in a molar ratio of 1 : 2. CuCl, CuCl2, or Cu(NO3)2 ⋅ 3H2O were added as copper sources. Underpotential deposition (UPD) of Cu precedes bulk deposition in chloride as well as nitrate electrolytes. Cu deposition from Cu+ in chloride media is observed as a one‐electron reaction, whereas deposition from Cu2+ occurs in two steps since Cu+ is strongly stabilized by chloride. Cu+ is less stabilized by nitrate and the beginning of bulk deposition in the nitrate‐containing DES with Cu2+ is shifted by several hundred mV to more positive potentials compared to the chloride DES. A diffusion‐controlled, three‐dimensional nucleation and growth mechanism is found by chronoamperometric measurements and analysis based on the model of Scharifker and Mostany.

Unconventional Electrochemical Behaviors of Cu Underpotential Deposition in a Chloride-Based Deep Eutectic Solvent: High Underpotential Shift and Low Coverage

“…The current peaks C4/A4 are assigned to Cu OPD and its anodic dissolution. These characteristics are consistent with that reported in the literature. ,− In addition to the above current peaks, two pairs of smaller current peaks (C2/A2 and C3/A3) can be observed at around +0.62 and +0.07 V, respectively. To delve into the details, we narrowed down the potential region of CV to avoid interference from peaks C1/A1 and C4/A4 (Figure b).…”

“…While OPD of Cu in DESs has been investigated to elaborate a variety of factors affecting the deposition kinetics, − studies on UPD of Cu at the microscopic level are completely lacking, though it is crucial for understanding the initial stage of Cu deposition. Cyclic voltammetry measurements of Cu UPD on Au(111) electrodes in reline presented two pairs of current peaks in the underpotential region, which are similar to that in an aqueous solution containing chloride ions; i.e., chloride ions may also be involved in the formation of the Cu UPD adlayer .…”

Ice crystal-assisted intercalation of PANI within Ti3C2Tx MXene thin films for flexible supercapacitor electrodes with simultaneously high mechanical strength and rate performance

“…Furthermore, a b -value of 0.94 is obtained for the anodic peaks of the I-PANI/MXene electrode, which is not only higher than that of the control samples but also comparable to or higher than the values reported in previous studies. 52–54 All of these results confirm that our prepared I-PANI/MXene electrode possesses a predominantly nondiffusion limited capacitive behaviour, which is favourable for achieving superior rate capability.…”

Entropic Contributions to Sodium Solvation and Solvent Stabilization upon Electrochemical Sodium Deposition from Diglyme and Propylene Carbonate Electrolytes

“…As can be clearly seen in Figure 2 (b), after a few seconds, when the potential drops below about 1 V, the (negative) slope of the frequency curve increases, signaling strong deposition of material onto the electrode. The related mass change per moles of electrons was determined from the Sauerbrey equation [13] analogously to the procedure of Geng and co-workers, [14] resulting in about 60 g mol À 1 . This is well above the expected value for Na deposition (23 g mol À 1 ) and points to the deposition of a reaction product with high molecular weight, which indicates the ongoing formation of the SEI.…”