Electrochemical Synthesis of Unique Nanomaterials in Ionic Liquids

Abstract

The review considers the features of the processes of the electrochemical synthesis of nanostructures in ionic liquids (ILs), including the production of carbon nanomaterials, silicon and germanium nanoparticles, metallic nanoparticles, nanomaterials and surface nanostructures based on oxides. In addition, the analysis of works on the synthesis of nanoscale polymer films of conductive polymers prepared using ionic liquids by electrochemical methods is given. The purpose of the review is to dwell upon an aspect of the applicability of ILs that is usually not fully reflected in modern literature, the synthesis of nanostructures (including unique ones that cannot be obtained in other electrolytes). The current underestimation of ILs as an electrochemical medium for the synthesis of nanomaterials may limit our understanding and the scope of their potential application. Another purpose of our review is to expand their possible application and to show the relative simplicity of the experimental part of the work.

Keywords: electrochemistry; electrosynthesis; ionic liquids; nanomaterials; nanostructure.

Figure 1

Formation of domains in [C₆MIm][PF₆] (reprinted with permission from [48]. Copyright 2015 The Royal Society of Chemistry).

Figure 2

Schematic of ion clusters surrounding nanoparticles. (reprinted with permission from [48]. Copyright 2015 The Royal Society of Chemistry).

Figure 3

Near-surface layers on charged and uncharged surfaces and their effect on volume flow of ILs. (reprinted with permission from [60]. Copyright 2016 The American Chemical Society).

Figure 4

(a) Typical IL; (b) typical DES (reprinted with permission from [71]. Copyright 2015 The Royal Society of Chemistry).

Figure 5

SEM photo of the modified surface of sintered fibers of FeCrAl obtained by anodic treatment in ionic liquid BMIM-Ac (reprinted with permission from [110]. Copyright 2016 The Springer Nature.

Figure 6

Microphotograph of a fragment of the titanium anode obtained by galvanostatic oxidation in ionic liquid BMImCl in the presence of water additives [143].

Figure 7

(a) SEM photo of a microstructure of the nickel and (b) stainless steel surface after polishing in BMimNTf₂ at a constant current (reprinted with permission from [37]. Copyright 2014 The American Chemical Society).

Figure 8

SEM photo of the surface after anodic treatment at a constant current in BMImCl in the presence of propylene glycol (1:1). (a) microstructure of titanium (reprinted with permission from [150]. Copyright 2011 The Royal Society of Chemistry); (b) microstructure of nickel [144].

Figure 9

SEM photo of the microstructure of the titanium surface after anodic treatment in BMImNTf₂, propylene glycol (1:1) under different conditions: (a) galvanostatic or (b) potentiostatic [152].

Figure 10

SEM photos of a fragment of the surface of a titanium foil anodized at direct current in the BMImNTf₂ ILs with the addition of propylene glycol illustrating the growth of nanotubes from the hexagonal cellular ordered structures at a different magnification: (c) 50,000×; (a) 100,000×; (b) 300,000× (reprinted with permission from [148]. Copyright 2017 The Elsevier).

Figure 11

(a) SEM photo of the microstructure of a fragment of oxide nanoroll decorated with oxide nanotubes and (b) the scheme of preparation of such a structure by anodic oxidation of amorphous alloy Fe70Cr15B15 in ionic liquid BMimBF₄. (reprinted with permission from [155]. Copyright 2021 The American Chemical Society).

Figure 12

Cyclic voltammograms of ionic liquid [BMIm⁺][BF₄⁻] in the presence of pyridine on a (a) Re and (b) Pt electrode. Reference electrode–Ag wire (the inset shows CV of [BMIm⁺][BF₄⁻] and ionic liquid mixed with water (volume ratio 1:1). The scanning rate is 100 mV/s). (Reprinted with permission from [160]. Copyright 2016 Elsevier).

Scheme 1

Scheme of the formation of conductive oligomer: (a) the formation of anion-radical, (b) formation of polypyridine and (c) its doping (reprinted with permission from [160]. Copyright 2016 Elsevier).

Scheme 1

Scheme of the formation of conductive oligomer: (a) the formation of anion-radical, (b) formation of polypyridine and (c) its doping (reprinted with permission from [160]. Copyright 2016 Elsevier).

Figure 13

SEM photo of the fragment of the Re surface: (a) initial state, (b) after 100 cycles and (c) SEM photo of the fragment of the Pt surface after 100 cycles (reproduced from [160] with permission from Elsevier).

Scheme 2

Scheme of a bipolar gold electrode placed between two golden counter-electrodes (reprinted with permission from [166]. Copyright 2021 The American Chemical Society).

Scheme 3

Structure of monomer ILs (reprinted with permission from [174]. Copyright 2010 John Wiley and Sons).