Ionic Liquids-Based Iron Phosphide/Carbon Nanotubes Composites: High Active Electrocatalysts towards Hydrogen Evolution Reaction

Ionic Liquids as Promisingly Multi-Functional Participants for Electrocatalyst of Water Splitting: A Review

Ionic liquids (ILs), as one of the most concerned functional materials in recent decades, have opened up active perspectives for electrocatalysis. In catalyst preparation, ILs act as characteristic active components besides media and templates. Compared with catalysts obtained using ordinary reagents, IL-derived catalysts have a special structure and catalytic performance due to the influence of IL’s special physicochemical properties and structures. This review mainly describes the use of ILs as modifiers and reaction reagents to prepare electrocatalysts for water splitting. The designability of ILs provides opportunities for the ingenious composition of cations or anions. ILs containing heteroatoms (N, O, S, P, etc.) and transition metal anion (FeCl4−, NiCl3−, etc.) can be used to directly prepare metal phosphides, sulfides, carbides and nitrides, and so forth. The special physicochemical properties and supramolecular structures of ILs can provide growth conditions for catalysts that are different from the normal media environment, inducing special structure and high performance. ILs as heteroatom sources are safe, green and easy to operate compared with traditional heteroatom sources. The strategy for using ILs as reagents is expected to realize 100% atomic transformation of reactants, in line with the concept of green chemistry. This review reflects the discovered work with the best findings from the literature. It will offer readers a deeper understanding on the development of IL-derived electrocatalysts and inspire them to ingeniously design high-performance electrocatalysts for water splitting.

Ionic Liquid-Based Polymer Nanocomposites for Sensors, Energy, Biomedicine, and Environmental Applications: Roadmap to the Future

Current interest toward ionic liquids (ILs) stems from some of their novel characteristics, like low vapor pressure, thermal stability, and nonflammability, integrated through high ionic conductivity and broad range of electrochemical strength. Nowadays, ionic liquids represent a new category of chemical-based compounds for developing superior and multifunctional substances with potential in several fields. ILs can be used in solvents such as salt electrolyte and additional materials. By adding functional physiochemical characteristics, a variety of IL-based electrolytes can also be used for energy storage purposes. It is hoped that the present review will supply guidance for future research focused on IL-based polymer nanocomposites electrolytes for sensors, high performance, biomedicine, and environmental applications. Additionally, a comprehensive overview about the polymer-based composites' ILs components, including a classification of the types of polymer matrix available is provided in this review. More focus is placed upon ILs-based polymeric nanocomposites used in multiple applications such as electrochemical biosensors, energy-related materials, biomedicine, actuators, environmental, and the aviation and aerospace industries. At last, existing challenges and prospects in this field are discussed and concluding remarks are provided.

Functions and performance of ionic liquids in enhancing electrocatalytic hydrogen evolution reactions: a comprehensive review

As a green and renewable energy source, hydrogen can be produced by the electrolysis of water via the hydrogen evolution reaction (HER). Nevertheless, this method requires efficient and low-cost electro-catalysts to improve hydrogen production efficiency. Ionic liquids (ILs), with a unique combination of such superior properties as low vapor pressure, high electrical conductivity, high electrochemical stability, and a wide variety of functional groups, have found applications in electrochemical systems designed for efficient HER. Herein, we provide a comprehensive and updated review on the functions and performance of ILs used in electrochemical systems to enhance the HER. As the name suggests, ILs have been employed either as electrolytes by themselves, or as electrolyte additives. They also played many functional roles in the synthesis of HER electrocatalysts, including as the synthesis reaction solvent, reaction precursor as well as single/dual ion sources, binder and structure-directing agents of the catalysts. With the assistance of ILs, HER efficiency of electrocatalysts was improved significantly, resulting in decreased overpotentials in the range of 16–385 mV @ 10 mA cm⁻² and increased Tafel slopes in the range of 30–210 mV dec⁻¹. Lastly, the problems and challenges of ILs in electrocatalytic water electrolysis and HER are also discussed and their prospects considered.

Ionic liquids play multi-functions in synthesizing catalysts for HER such as electrolytes/electrolyte additives, reaction solvents, precursors, single/dual ion sources, binders, or morphological structure/phase structure directing agents.

The in situ preparation of iron phosphide using ionic liquids as iron and phosphorus sources for efficient hydrogen evolution reactions

Ionic liquids (ILs) were utilized as iron and phosphorus sources for the preparation of iron phosphide for the first time. The IL trihexyl(tetradecyl)phosphonium tetrachloroferrate ([P(C6H13)3C14H29][FeCl4]) and carbon nanotubes (CNTs) were applied as precursors for the in situ preparation of Fe2P(IL6)/CNTs. This material has good catalytic activity and stability for the hydrogen evolution reaction, including a low onset overpotential (75 mV) and Tafel slope (68 mV dec-1). Moreover, this catalyst exhibits current densities of 10 and 20 mA cm-2 at overpotentials of 115 and 150 mV, respectively. The phosphidation process using [P(C6H13)3C14H29][FeCl4] was also investigated. All experimental results indicate that Fe2P can be formed in situ on the CNTs using this IL, and that the CNTs help the formation of the Fe2P nanoparticles and improve the electrical conductivity. This IL-based in situ preparation strategy is facile and environmentally friendly and does not require the addition of other reagents. This method holds great promise for application in other electrochemical studies.