**2.5 Non-aqueous boron-based electrolyte for electrodeposition**

This section discusses the electrodeposition of metals from non-aqueous BBILs. The application of non-aqueous BBILs makes it feasible to obtain cathodic residues of metals or metallic alloys that cannot be deposited by conventional electrolysis of aqueous solutions. Since the hydrogen overpotential is relatively low, it does not allow some electrodeposition reactions to occur in aqueous solutions. Due to the intrinsic conductivity of ILs, many metals and semiconductors may be electrodeposited directly from an IL solution of metal ions or metal-ILs ion complexes using standard electrowinning techniques. Because of the low volatility of IL, the procedure may be carried out at high temperatures exceeding 100°C. The number of studies published on non-aqueous solution electrodeposition has grown in recent years [33].

Yanna NuLi and colleagues [81] investigated highly reversible magnesium precipitation and dissolution processes in the ionic liquid of 1 Mg (CF3SO3)2 and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIMBF4]. According to the scanning electron microscopy (SEM) data, micrometric-sized, virtually pyramidal-shaped magnesium deposits appeared, and when the magnesium dissolved, the electrode became clean and film-free. Cyclic voltammograms of Mg accumulation-dissolution also show that these reactions are reversible. [BMIMBF4] demonstrated especially promising properties in terms of electrochemical window (Pt vs. 4.2 V) and

#### **Figure 11.**

*Water electrolysis in ILs electrolyte mixture.*

magnesium deposition-dissolution efficiency. As a result, this method may be acceptable for application in rechargeable Mg batteries.

Survilien et al. [82] studied the electrodeposition of the chromium from the ionic liquid [BMIMBF4] and chromium chloride. The cathodic process of chromium electrodeposition procedure from the ionic liquid used was as follows: electrochemical reduction of water molecules, followed by chemical degradation of [BF4] ions. According to the findings of this investigation, [BMIMBF4] can be deemed promising for hazardous Cr (VI) baths for black chrome plating.

Menzel et al. [83] examined the development of the mechanism of the ZnO nanowire growth model by studying [BMIMBF4] as an ionic liquid. They concentrated on the effects of IL sources on nanowire development in this work. They discovered that because B is an n-type source of ZnO material, IL-promoted growth may be employed to recruit donors. Electrical measurements of XPS and ZnO nanowires validated these hypotheses. Electrical measurements revealed that ionic liquidassisted growth improved electrical conductivity (=0.09 cm). [BMIMBF4] IL-assisted nanowire growth showed that boron was significantly involved in the alteration of nanowire growth properties compared to pure ZnO nanowire growth.

For electrodeposition, another IL, [C2mim] [BF4], was utilized. Steichen M and Dale P [84] investigated the electrodeposition of trigonal selenium (t-Se) nanorods from [C2mim][BF4]/[C2mim]Cl at high temperatures (*T* > 100°C).phase, morphology, and crystallinity of Se residues vary, the choice of precursor salts also controls the electrodeposition of selenium. They demonstrated for the first time that t-Se nanorods may be made at high temperatures using a template electrodeposition route from [C2mim][BF4]/[C2mim]Cl. The crystal quality of t-Se nanorods improves when the temperature rises above 100°C.

*Investigation of Boron-Based Ionic Liquids for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.105970*

**Figure 12.** *Structure of ILs designed capture of CO2 (adapted from Ref. [85, 86]).*

According to the researchers, photoactive t-Se nanorods with p-type conductivity have been detected in an ionic liquid for the first time. Photoelectrochemical measurements performed in ionic liquid confirmed the p-type conductivity of t-Se nanorods.

#### **2.6 Carbon dioxide capture using BBILs**

The use of ILs to help separate CO2 from other gases has recently become a hot topic of activity both in academia and industry. ILs' lack of volatility is a particular advantage in CO2 absorption over molecular liquid absorbers. Carbon capture has become legally mandatory for electric power plants to operate. However, there is a net cost of carbon capture, and these costs are passed on to consumers. For this reason, it is critical to design and synthesize efficient CO2 capture ILs made from the most basic and inexpensive building blocks, especially since the volumes required to achieve CO2 capture using ILs would be prohibitively expensive at envisioned scales [85, 86]. In recent years, many publications have appeared on IL-CO2 interactions of one kind or another (**Figure 12**).

Certain functional groups in the ionic liquid, such as anions of the amide family, absorb CO2 up to 0.5 mol/mol IL through the traditional carbamate reaction. CO2 absorption is enabled via similar functionalization through direct contact with amine or anionic functional groups. In addition, several ionic liquids also show potential in other environmentally conscious applications, such as CO2 capture. Some of these novel "task-specific" ionic liquids have shown promise in CO2 capture.

Using the ionic liquids 1-*n*-butyl-3-methylimidazolium hexafluorophosphate [BMIM] [PF6 − ] and [BMIM] [BF4 − ], Anthony et al. [87] investigated CO2 capture. They also compare CO2 collection utilizing these ILs to conventional monoethanolamine-based technologies. According to the findings, [BMIM] [PF6 − ] is particularly effective in capturing CO2 from a mixture of N2 or CH4. As a result, these ILs are a viable choice for CO2 capture in order to create an ionic liquid with a carrying capacity comparable to monoethanolamine.
