Can Dicyanamide Ionic Liquids Boost Water Electrolysis?

Abstract

Room-temperature ionic liquids (RTILs) have attracted attention in engineering electrolytes for electrochemical energy conversion and storage devices. Within the present study, five different RTILs were prepared and subsequently investigated as additives to alkaline aqueous solutions for the oxygen evolution reaction (OER). Studied RTILs were based on dicyanamide ion as a green anion, suitable for electrochemical applications, and included 1-butyl-3-ethylimidazolium dicyanamide, 1,3-dibutylimidazolium dicyanamide, 1-butyl-3-hexylimidazolium dicyanamide, 1-butyl-3-octylimidazolium dicyanamide, and 1,3-diethylimidazolium dicyanamide. The OER studies were performed in 8 M KOH with RTILs (1 vol.%) using linear scan voltammetry, and the current densities were compared to those recorded in 8 M KOH with no RTILs added. Reaction parameters, such as the Tafel slope, were determined, enabling further evaluation and comparison of RTIL-containing electrolyte systems. Moreover, the influence of temperature on the OER efficiency of the system with mixed RTIL-KOH electrolytes was studied. Voltammetric studies were complemented by electrochemical impedance spectroscopy, which revealed a decrease in solution resistance with increasing temperature, as well as by chronoamperometry analysis.

1. Introduction

Alkaline water electrolysis is one of the most promising and environmentally friendly methods for hydrogen production. Water splitting occurs through two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode, with the OER generally requiring higher overpotentials [1]. The complex mechanism of OER involves the transfer of 4 electrons through several single-electron transfer steps, with each step contributing to the overall high energy barrier [2,3]. Equations (1) and (2), where * denotes the electrocatalyst’s active site, illustrate the initiation of the adsorbate-evolution mechanism of the OER in alkaline media [4]. Molecular O₂ can then be generated either by the direct combination of two O species (Equation (3)) or via the formation of OOH (Equation (4)) followed by its decomposition to O₂ (Equation (5)).

$$\ast +\mathrm{O}{\mathrm{H}}^{-}\to \ast \mathrm{O}\mathrm{H} + {\mathrm{e}}^{-}$$

(1)

$$\ast \mathrm{O}\mathrm{H}+\mathrm{O}{\mathrm{H}}^{-}\to \ast \mathrm{O}+{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}+ {\mathrm{e}}^{-}$$

(2)

$$2 \ast \mathrm{O}\to 2 \ast +{\mathrm{O}}_{2\left(\mathrm{g}\right)}$$

(3)

$$\ast \mathrm{O}+\mathrm{O}{\mathrm{H}}^{-}\to \ast \mathrm{O}\mathrm{O}\mathrm{H}+{\mathrm{e}}^{-}$$

(4)

$$\ast \mathrm{O}\mathrm{O}\mathrm{H}+\mathrm{O}{\mathrm{H}}^{-}\to \ast +{\mathrm{O}}_{2\left(\mathrm{g}\right)}+{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)} + {\mathrm{e}}^{-}$$

(5)

There is an exhaustive search for novel electrode materials that would lead to a decrease in the overpotential necessary and, consequently, to a reduction in energy consumption and overall electrolysis cost [5,6]. Another possible way to increase the efficiency of the water electrolysis process is through electrolyte engineering [7]. Room temperature ionic liquids (RTILs) have garnered attention for their use in hydrogen energy as electrocatalyst precursors, as membrane components, and as electrolytes [5,8]. Their use as electrolytes, particularly as additives to electrolytes in alkaline water electrolyzers, results from their exceptional properties, including a wide electrochemical potential window and low vapor pressure [9,10]. Furthermore, they can be used without a supporting electrolyte (due to the abundance of charge-carrying ions), making them more eco-friendly than volatile organic solvents (due to their near-zero volatility), and they are thermally and chemically stable (due to the ions’ chemical robustness) [11,12]. Thus, pristine RTILs have been reported as electrolytes for rechargeable batteries [13,14,15] and supercapacitors [13,14], but also as solvents of electrolyte salt, compounded with conventional electrolytes, or for RTIL-based (gel/solid) polymer and ionogel electrolytes [16,17]. Furthermore, they were studied as additives to electrolytes for HER; RTILs were shown to enhance the electrolyte properties and improve the process efficiency at room temperature [17,18].

Properties of RTILs, such as viscosity, density, conductivity, melting and decomposition temperatures, and hydrophobicity/hydrophilicity, are determined by the choice of cation and anion, where there is an endless number of cation/anion combinations [19]. The electrochemical window is determined by the reduction and oxidation potential of the cationic and anionic components, respectively [10].

Recent studies indicate that introducing RTILs in the electrolyte or during the fabrication of electrocatalysts can significantly enhance the OER performance [20,21,22,23]. Different RTILs used as electrolyte additives, such as 1-ethyl-3-methylimidazolium chloride [EMIM]Cl, 1-ethyl-3-methylimidazolium bromide [EMIM]Br, and 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM]ESO₄, have shown lower anodic potentials and Tafel slopes during OER [24]. RTILs could be a good option as electrolytes because they provide suitable stability during oxygen reactions, for instance, in Mg–air batteries [25]. Consequently, magnesium-containing N-butyl-N-methylpyrrolidinium bis (trifluoromethanesulfonyl)imide ([BMP][TFSI]) additives on oxygen reduction reaction (ORR)/OER were investigated in Mg–air batteries [25]. The impact of 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄) additive on OER kinetics during zinc electrowinning was investigated, revealing an increased OER rate constant and a significantly decreased resistance value [26].

Within the present study, five different RTILs based on the dicyanamide anion (DCA⁻) were synthesized and evaluated as electrolyte additives for OER in alkaline water electrolysis. DCA was chosen as a green (non-fluorinated) anion, suitable for electrochemical tests. Specifically, DCA⁻ is highly charge-delocalized, with the negative charge distributed over nitrogen and carbon atoms. This delocalization weakens ion-ion interactions and hydrogen bonding, leading to reduced viscosity and increased ion mobility. The absence of fluorine minimizes environmental concerns and potential hydrolysis to corrosive species. DCA-based RTILs have been investigated for their interactions with metal anodes in metal-ion batteries [27], offering a cost-effective route to stabilize lithium and sodium electrochemistry [28,29]. These RTILs also enable reversible cycling of divalent metals like zinc [30]. However, the interfacial behavior and electrochemical stability of DCA-based RTILs vary with the metal type [31]. For example, in sodium metal systems, long-term plating/stripping is hindered due to the presumed instability of DCA⁻, which leads to electrode passivation, especially in the presence of moisture [28]. Similar challenges are observed in magnesium systems, where DCA⁻ anions form crystalline complexes that impede charge transport [32]. To address these limitations in monovalent systems, mixing the metal salt with a different anion than that of the RTIL has shown promise. It is hypothesized that strong cation–anion interactions govern interfacial layering and anion decomposition. Electrochemical and surface analysis techniques confirm that ion speciation and interfacial behavior at the electrode can be tuned through the careful selection of the anion.

2. Materials and Methods

2.1. Synthesis of the Room-Temperature Ionic Liquids

Five room-temperature ionic liquids (

Table 1. DCA ionic liquids synthesized within the present study.

RTIL	1-butyl-3-ethyl imidazolium dicyanamide	1-butyl-3-octyl imidazolium dicyanamide	1,3-dibutyl imidazolium dicyanamide	1,3-diethyl imidazolium dicyanamide	1-butyl-3-hexyl imidazolium dicyanamide
Label	BEIm DCA	BOIm DCA	BBIm DCA	EEIm DCA	BHIm DCA
Cation
Anion

) were synthesized via a two-step procedure, as shown in Scheme 1. Within the first step, quaternization, the free N atom on the imidazole was alkylated and converted into a quaternary ammonium ion. The starting compounds were ethyl imidazole and butyl imidazole, which reacted with halogenoalkanes (ethyl, butyl, hexyl, and octyl chloride) to form chloride RTILs. Ethyl imidazole and chloroethane (for example) were dissolved in ethyl acetate, forming a homogeneous solution. The solution was placed in a reflux apparatus and heated at 120–150 °C for ~12 h. At the end of the reaction, two phases were obtained: a denser lower phase containing the chloride RTIL (insoluble in ethyl acetate) and a lighter upper phase of ethyl acetate, possibly containing unreacted components. The phases were separated using a separatory funnel. The RTIL phase was washed three times with fresh portions of ethyl acetate, with shaking after each addition, to extract residual organic components. The remaining ethyl acetate was removed from the RTIL using a rotary evaporator, yielding a pure chloride RTIL that could be used directly or subjected to further processing.

Dicyanamide (DCA) RTILs were obtained by the anion exchange of the chloride RTILs. The chloride RTIL was dissolved in acetone, and an equimolar amount of NaDCA salt was added. The resulting NaCl dissolved very poorly in acetone and precipitated. The sediment was separated by squeezing it through a G4 sieve with the help of a vacuum, resulting in an RTIL with DCA as an anion. Acetone was evaporated using a rotavapor, and the obtained DCA RTIL was stored in a desiccator under P₂O₅.

2.2. Electrochemical Methods and Measurements

Electrochemical performance was evaluated using a PAR273A potentiostat (Princeton Applied Research, Inc., Oak Ridge, TN, USA). The electrochemical measurements were performed in a 3-electrode setup, with a Pt foil serving as the working electrode, a saturated calomel reference electrode, and a Pt wire as the counter electrode. All potentials were subsequently converted to the reversible hydrogen electrode (RHE) scale. Thus, potential values shown in the work are referenced to the RHE, unless otherwise noted. The electrolyte used was 8 M KOH with the addition of 1 vol.% of the corresponding RTIL. The same set of measurements was carried out in pure 8 M KOH for comparison purposes. Linear scan voltammetry was performed from the open-circuit potential to 1.85 V. Electrochemical impedance spectroscopy (EIS) was conducted in the frequency range of 100 kHz to 0.01 Hz at potentials of 1.50, 1.65, and 1.85 V. The collected EIS data were modeled using ZView software 3.5i (Scribner Associates, Inc., Southern Pines, NC, USA). Chronoamperometry was performed at 1.85 V for 3600 s. The influence of temperature was examined in the 25–85 °C range.

3. Results and Discussion

Studies on the effect of DCA RTILs as electrolyte additives on the OER kinetics and efficiency were conducted using a platinum (Pt) electrode in an 8 M KOH electrolyte solution. Pt was employed as the working electrode in this study of the OER for its excellent stability, good electrical conductivity, and moderate catalytic activity. Although Pt is not the most active OER catalyst across all conditions, its well-defined surface properties and reproducibility render it a valuable model system for fundamental mechanistic investigations [33]. 8 M KOH supporting electrolyte corresponds to the concentration of KOH typically used in industrial alkaline electrolyzers. Voltammograms recorded in 8 M KOH + RTILs (1 vol.%) electrolyte reveal that the OER starts the earliest in the electrolyte containing BOIm DCA and EEIm DCA [34], as shown in Figure 1A. However, the reaction rate in the case of EEIm DCA is lower than in the case of electrolytes with BOIm DCA, as well as BBIm DCA and BHIm DCA. Thus, the highest current densities in the studied potential range were recorded in the case of the BOIm DCA-containing electrolyte. Tafel plots for OER in KOH with five RTIL additives were next constructed (Figure 1B), and Tafel slope, b, values were determined to range from 134 to 178 mV dec⁻¹. Namely, Tafel slopes were 134 mV dec⁻¹ for BBIm DCA, 135 mV dec⁻¹ for BHIm DCA, 148 mV dec⁻¹ for BEIm DCA, 153 mV dec⁻¹ for BOIm DCA, and 178 mV dec⁻¹ for EEIm DCA.

An apparent decrease in charge-transfer resistance is observed with increasing potential during the EIS measurements, as shown in Figure 1C. A low ohmic resistance of the electrolyte solution (R_s < 2 Ω) was observed in all studied RTIL systems (Figure 1C,D). Conversely, the charge-transfer resistance R_ct at the electrode/electrolyte interface was found to differ depending on the RTIL additive (Figure 1D). The lowest charge-transfer resistance, as low as ca. 11 Ω, was observed in the case of BOIm DCA, BBIm DCA, and BEIm DCA. The charge-transfer resistance in the case of BHIm DCA was somewhat higher, i.e., ca. 17 Ω. Finally, the EIS study revealed the highest charge-transfer resistance of ca. 145 Ω in the case of the electrolyte containing EEIm DCA, which explains the low current densities observed in that case. Namely, the OER in the Pt/8 M KOH + EEIS DCA system appears to be thermodynamically favorable but kinetically hindered. The low onset potential of the OER indicated that the reaction begins at a relatively small driving force. At the same time, the observed high charge-transfer resistance suggested that once initiated, the interfacial kinetics are slow. The onset potential is influenced by surface chemistry and activity of catalytic sites, which can be modulated by the electrolyte composition, i.e., its pH, ionic strength, and type of cation/anion. Specifically, the onset potential of OER in alkaline electrolyte is influenced by the interaction of OH⁻ ions with surface-active sites. The Pt electrode/8 M KOH + EEIm DCA electrolyte interactions stabilized surface species and tuned adsorption energy, favoring the initial adsorption of OH⁻, i.e., enabling the strong adsorption and activation of OH⁻ (Equation (1)). This further resulted in a lower thermodynamic overpotential, allowing the reaction to start at a relatively low onset potential. In contrast, the charge-transfer resistance is governed by overall electrode–electrolyte interfacial kinetics and charge transport properties once the OER has initiated. Sluggish OH⁻ desolvation (i.e., shedding part of their hydration shell to enable adsorption on the electrode surface, Equation (2)) or specific ion–electrode interactions (such as O–O bond formation, Equation (4)) hindering the electron transfer after the first step, may lead to a high charge-transfer resistance and overall sluggish reaction kinetics even if the onset potential is low.

Further studies were conducted with BOIm DCA (which delivered the highest performance at 25 °C) and BEIm DCA (which delivered moderate performance at 25 °C), and were compared to pure KOH. The influence of temperature on OER kinetics in an * M KOH, 8 M KOH + BOIm DCA or BEIm DCA electrolyte was examined in the 25–85 °C range (Figure 2A–C), as commercial alkaline water electrolyzers typically operate in the 65–90 °C range [35]. Current densities, j, increased with the increase in temperature, T; thus, j values using the BOIm DCA additive increased over four times, i.e., from 10.4 mA cm⁻² to 42.5 mA cm⁻² when the temperature increased from 25 °C to 85 °C. Similarly, the current density for the BEIm DCA case at 85 °C (18.8 mA cm⁻² at 1.85 V) was almost four times higher than that at 25 °C (5.1 mA cm⁻² at 1.85 V) (Figure 2C). Still, the highest current densities were recorded in 8 M KOH (Figure 2A), thus raising a question of whether DCA RTILs can boost OER kinetics. The apparent activation energy, E_a, was calculated using the Arrhenius equation, i.e., from the slope of ln j vs. T⁻¹ plot (Figure 2D). The E_a value was determined to be 33 kJ mol⁻¹ for 8 M KOH, 31 kJ mol⁻¹ for BOIm DCA additive, and 28 kJ mol⁻¹ for BEIm DCA additive. It should be noted that the correlation factor, R², was lower than 0.99 due to the issue described below regarding gas bubble management.

The overpotential, η₁₀, required to reach a current density of 10 mA cm⁻² was observed to decrease with increasing temperature. The η₁₀ values of 330, 410, and 519 mV were determined for BOIm DCA additive, pure 8 M KOH, and BEIm DCA additive, respectively, at 85 °C. On the other hand, the overpotential at 10 mA cm⁻² was 624 and 550 mV for BOIm DCA and pure 8 M KOH, while the current density of 10 mA cm⁻² was not reached at 25 °C in the studied potential region in the case of BEIm DCA.

Contrary to expectation, Tafel slope values did not decrease with an increase in temperature;

Table 2. Tafel analysis parameters obtained for OER at a Pt electrode in 8 M KOH without and with BEIm DCA at different temperatures.

T/°C	25	35	45	55	65	75	85
8 M KOH
b/mV dec−1	135	144	131	129	175	205	-
α	0.44	0.42	0.48	0.51	0.38	0.34	-
8 M KOH + BEIm DCA
b/mV dec−1	148	122	135	160	209	255	266
α	0.44	0.50	0.47	0.41	0.32	0.27	0.27

illustrates the case of 8 M KOH without and with BEIm DCA.

No clear trend in Tafel slope values with temperature most likely originates in intense bubbling, where formed O₂ gas bubbles at the electrode surface block the active sites, decreasing the available electrochemically active surface area [36].

Analyzing the Tafel slope in gas-evolving reactions is challenging due to the formation of gas bubbles on the electrode surface [36,37,38]. These bubbles form depending on the gas concentration in the liquid, which is affected by mass transfer and current density. Typically, during gas evolution, a layer of gas bubbles builds up on the electrode surface, and its extent depends on both the current density and the properties of the anode. The condition of the electrode surface plays a key role, as bubbles tend to nucleate at specific, irregular spots on the surface [36,38]. Herein, with the increase in cell temperature, the Tafel slopes increased from 133 to 266 mV dec⁻¹ in 8 M KOH + BEIm DCA electrolyte and from 135 to 205 mV dec⁻¹ in 8 M KOH; this similar observation in two different electrolytes suggests that the lack of decreasing trend is indeed due to the bubble attachment on the electrode surface rather than change in reaction mechanism.

Moreover, a change in the electrolyte color was observed with an increase in temperature, as shown in Figure 3 for the BEIm DCA-containing electrolyte. Similarly, in the case of BOIm DCA-containing electrolyte, the color changed from transparent to light yellow and then to orange-brown as the temperature rose.

The H-atom of BEIm DCA at position C2 (Scheme 2) shows acidic properties. At high concentrations of strong alkalis, deprotonation can occur in that position, resulting in the generation of a neutral ylidene system [39]. The disruption of delocalization in the imidazole ring is detrimental to the chromophore, resulting in a color change [40]. Carbene generation has been previously reported [41,42]. Herein, it is assumed that this reaction is more pronounced at higher temperatures, i.e., a higher amount of carbene is present in equilibrium.

OER in 8 M KOH + BOIm DCA and BEIm DCA (1 vol.%) electrolyte at different temperatures was also investigated by EIS (Figure 4A–C), and data were fitted using the one-time constant equivalent circuit presented in Figure 4D.

Table 3. Parameters obtained from the EIS data at different temperatures for the OER at the Pt electrode in 8 M KOH + BEIm DCA (1 vol.%) at an applied potential of 1.8 V.

T/°C	Rs/Ω cm2	C/μF cm−2	Rct/Ω cm2
25	0.672 ± 0.007	336.4	10.1 ± 0.2
35	0.69 ± 0.01	120.3	12.7 ± 0.2
45	0.60 ± 0.01	64.0	12.4 ± 0.3
55	0.60 ± 0.01	48.2	13.5 ± 0.3
65	0.499 ± 0.005	38.3	14.6 ± 0.1
75	0.478 ± 0.008	35.4	9.3 ± 0.2
85	0.518 ± 0.007	32.7	6.19 ± 0.06

summarizes the resistance and capacitance determined as fitting parameters for the case of BEIm DCA. The OER impedance data analysis shows that both the electrolyte resistance, R_s, and the charge-transfer resistance, R_ct, increased with increasing temperature from 25 to 65 °C, and then decreased with further increase in temperature to 85 °C. Generally, improvement of OER kinetics at higher temperatures is expected due to the decreased electrolyte viscosity and increased ionic conductivity. These facilitate the OH⁻ desolvation and O₂ bubble release, thereby lowering the charge-transfer resistance and enhancing the OER kinetics. Still, this sometimes comes at the cost of reduced intermediate stabilization, i.e., stability/selectivity trade-off. Namely, the observed change in color at 65 °C and then at 85 °C suggested the formation of novel species at these temperatures, which alter the electrode/electrolyte interface and interactions, further affecting the charge transfer kinetics and reaction overpotentials.

When comparing the resistance at the lowest and the highest temperature, a decrease of R_ct at Pt/8 M KOH + BOIm DCA (1 vol.%) interface from 11 Ω at 25 °C to 3.7 Ω at 85 °C, and for Pt/8 M KOH + BEIm DCA (1 vol.%) interface from 10.1 Ω at 25 °C to 6.2 Ω at 85 °C was observed. EIS analysis of the Pt/KOH system under the same conditions revealed a comparable charge-transfer resistance value, with an observed “tail” in the low-frequency region, evidencing diffusion limitation of the process. Increased ion mobility (along with a reduced energy barrier) has been previously reported when using TEA-PS-BF₄ as an electrolyte for hydrogen production via water electrolysis [43]. Improved charge transport in the electrolyte reduces resistance and enhances the kinetics of the OER, resulting in higher current densities at a given overpotential. The favorable effects of DCA anion were expected due to its notably lower viscosity and, therefore, distinctly higher conductivity compared to the RTILs with NTf₂, which are also often used.

The positive effect of RTILs on the OER kinetics has been previously reported [24] when using 1-ethyl-3-methylimidazolium chloride [EMIM]Cl, 1-ehyl-3-methylimidazolium, bromide [EMIM]Br, and 1-ehyl-3-methylimidazolium ethyl sulfate [EMIM]ESO₄ as additives to electrolytes for OER at Pb-0.7%Ag anode.

The double-layer structure at the electrode/electrolyte interface can be altered in the presence of RTILs due to their unique ion pairing and structuring. This further alters the adsorption energies of OER intermediates (*OH, *O, *OOH) [44,45]. The modified electric double layer results in improved adsorption/desorption steps, which are essential parts of the OER mechanism (Equations (1)–(5)). It may also lower the generally high energy barrier for certain steps in the reaction pathway, thereby improving overall kinetics. In the case of hydrophobic RTILs, thin films suppress interfacial water structuring by limiting water content and hydrogen bonding [46]. This exclusion reduces the surface coverage and solvation of OH_ad species, weakening their interaction with the catalyst and thereby lowering the energy barrier for the final step of the OER.

In addition to increasing ionic conductivity and reaction kinetics, the DCA anion is not fluorinated (in contrast to, for instance, NTf₂, TSI, PF₆, and BF₄); therefore, it is environmentally far more acceptable. It is further electrochemically (as well as thermally) very stable, with the ability to stabilize the electrocatalyst as well. Namely, RTILs have been reported to “shield” the catalysts, preventing their degradation or aggregation, and consequently prolonging the electrode life and enabling consistent performance over long-term operation [47]. Figure 5 displays the chronoamperometric curve of the Pt electrode in 8 M KOH with the addition of BOIm DCA and BEIm DCA (1 vol.%) over 3600 s. The OER current densities at the 400th and 3600th seconds are compared, showing a decrease of ca. 27.1% and 48.1% for BOIm DCA and BEIm DCA, respectively. This behavior could be a consequence of the presence of numerous bubbles on the electrode surface, which blocks the available electrochemically active surface area, rather than the instability of the studied system [36].

As mentioned, vigorous bubble evolution during HER and OER has been reported to reduce the energy conversion efficiency of the water electrolysis process. Therefore, solutions focusing on a particular electrode design [48] or the use of ultrasound [49] for easier removal of bubbles from the electrode surface have been suggested. Yet again, the electrolyte was observed to play a notable role in bubble detachment; the diameter of bubbles detaching during OER was found to decrease with increasing electrolyte concentration, regardless of the specific ions present. This size reduction is attributed to changes in interfacial forces, particularly due to increased dynamic viscosity and altered surface tension in denser solutions [50]. This finding further directs electrolyte engineering for more energy-efficient water electrolysis.

4. Conclusions

Five room-temperature ionic liquids with a dicyanamide anion were prepared and studied as additives to aqueous alkaline electrolytes for OER. The effect of temperature on the OER efficiency of systems with pure KOH and mixed RTIL-KOH electrolytes was examined. Specifically, at 1.85 V, OER current densities in mixed RTIL-KOH electrolytes increased approximately four times when the temperature was increased from 25 to 85 °C. Still, the highest OER current densities were observed in 8 M KOH. The OER Tafel slope values for systems with pure KOH and mixed RTIL-KOH electrolytes were similar at lower temperatures. When increasing the temperature from 25 to 85 °C, Tafel slopes increased from 133 to 266 mV dec⁻¹ in the 8 M KOH + BEIm DCA electrolyte and from 135 to 205 mV dec⁻¹ in the plain 8 M KOH solution. Voltammetric measurements were complemented with electrochemical impedance spectroscopy, revealing resistance of the same order of magnitude across the studied systems. The chronoamperometric measurement in a mixed RTIL-KOH electrolyte showed a decrease in current density over 3600 s due to bubble gas formation and adsorption on the electrode surface during OER. In conclusion, the DCA⁻ anion could bring advantages due to its significantly lower viscosity and correspondingly higher ionic conductivity compared to commonly used fluorinated anions such as NTf₂. Furthermore, the DCA⁻ anion exhibits excellent electrochemical and thermal stability. Importantly, its non-fluorinated nature makes it a more environmentally benign alternative to fluorinated anions such as NTf₂, TSI, PF₆, and BF₄, thereby enhancing its appeal for sustainable applications in electrochemical systems. Still, further studies where attention would also be devoted to the gas bubble management are necessary.