This critical review outlines the current state-of-the-art research on the reversibly switchable wettability of surface brought about by external stimuli and the exchange of counterions. Chemical composition and surface topography are the two key factors in the wettability of solid substrates. Applying external stimuli and exchanging counterions of ionic liquids and polyelectrolyte films are valuable approaches for rendering the change in surface chemistry and/or topography, and for driving the transition between hydrophilicity and hydrophobicity of surfaces. Through the combination of stimuli-responsive films and micro-/nanostructural surfaces, smart surfaces with reversible switching between superhydrophobicity and superhydrophilicity have been achieved. As an important advancement in reversibly switchable wettability, this review briefly introduces ionic liquids (ILs) as on-off systems to obtain reversibly switchable wettability and then discusses in more detail the methods to induce the reversibly switchable wettability of surfaces modified by ILs, additives, or thin films. In addition to reversibly switchable wettability mechanisms, open problems and potential solutions are discussed (157 references).

Supported ionic liquids (SILs), which refer to ionic liquids (ILs) immobilized on supports, are among the most important derivatives of ILs. The immobilization process of ILs can transfer their desired properties to substrates. Combination of the advantages of ILs with those of support materials will derive novel performances while retaining properties of both moieties. SILs have been widely applied in almost all of fields involving ILs, and have brought about drastic expansion of the ionic liquid area. As green media in organic catalytic reactions, based on utilizing the ability of ILs to stabilize the catalysts, they have many advantages over free ILs, including avoiding the leaching of ILs, reducing their amount, and improving the recoverability and reusability of both themselves and catalysts. This has critical significance from both environmental and economical points of view. As novel functional materials in surface science and material chemistry, SILs are ideal surface modifying agents. They can modify and improve the properties of solids, such as wettability, lubricating property, separation efficiency and electrochemical response. With the achievements in the field of ILs, using magnetic nanoparticles (MNPs) to SILs has drawn increasing attention in catalytic reactions and separation technologies, and achieved substantial progress. The combination of MNPs and ILs renders magnetic SILs, which exhibit the unique properties of ILs as well as facile separation by an external magnetic field. In this article, we focus on imidazolium-based ILs covalently grafted to non-porous and porous inorganic materials. The excellent stability and durability of this kind of SILs offer a great advantage compared with free ILs and IL films physically adsorbed on substrates without covalent bonds. Including examples from our own research, we overview mainly the applications and achievements of covalent-linked SILs in catalytic reactions, surface modification, separation technologies and electrochemistry.

A highly efficient palladium acetate-catalyzed ligand-free Suzuki reaction in aqueous phase was developed in short reaction times (0.5-1 h) at 35 degrees C in air. The key for such a successful catalytic system was the use of a suitable amount of cosolvents in the aqueous phase. The method could be extended to the consecutive multi-Suzuki coupling, and polyaryls were prepared in a single one-pot step in high selectivity and excellent yield under mild reaction conditions (60 degrees C).

The palladium acetate-catalyzed coupling reaction of aryl boronic acid with carboxylic anhydride or acyl chloride was carried out smoothly in water in the presence of poly(ethylene glycol) (PEG) or 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) to give high yields of ketones without the use of phosphine ligands. The Pd(OAc)2-H2O-[bmim][PF6] catalytic system can be recovered and reused eight times with high efficiency for both carboxylic anhydride and acyl chloride.

Employing phosphonium-based ionic liquid, tetrabutylphosphonium chloride [P 4444 ]Cl as novel phosphorus source and reaction medium, a facile approach for fabricating nanostructured Ni 2 P and Ni 12 P 5 was developed upon microwave heating in 1−2 min or conventional heating at 350 °C for 3 h. In a microwave-driven approach, controlling counteranions of various nickel salts could conveniently tune the phase of as-synthesized nickel phosphides. Ni(acac) 2 and Ni(OAc) 2 •4H 2 O as Ni source could yield Ni 2 P nanoparticles, while NiCl 2 •6H 2 O and NiSO 4 •7H 2 O offered Ni 12 P 5 nanocrystals. The synthesized products were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Their electrocatalytic behavior toward hydrogen evolution reaction in acidic medium was investigated. The assynthesized Ni 2 P nanoparticles presented more excellent catalytic efficiency than Ni 12 P 5 . Ni 2 P nanoparticles from Ni(acac) 2 require overpotentials of only 102 mV to reach 10 mA cm −2 with a small Tafel slope of 46 mV dec −1 , showing its best activity among those tested catalysts. The present novel ionic liquid-mediated strategy for the synthesis of nickel phosphide provides the remarkable advantage of operating in very short time by microwave heating, which is of particular interest from the viewpoint of energysaving, fast synthesis, and easy operation.

No abstract

No abstract

The relationship between controllable morphology and electrocatalytic activity of Co O and CoSe for the oxygen evolution reaction (OER) was explored in alkaline medium. Based on the time-dependent growth process of cobalt precursors, 1D Co O nanorods and 2D Co O nanosheets were successfully synthesized through a facile hydrothermal process at 180 °C under different reaction times, followed by calcination at 300 °C for 2 h. Subsequently, 1D and 2D CoSe nanostructures were derived by selenization of Co O , which achieved the controllable synthesis of CoSe without templating agents. By comparing the electrocatalytic behavior of these cobalt-based catalysts in 1 m KOH electrolyte toward the OER, both 2D Co O and 2D CoSe nanocrystals have lower overpotentials and better electrocatalytic stability than that of 1D nanostructures. The 2D CoSe nanosheets require overpotentials of 372 mV to reach a current density of 50 mA cm with a small Tafel slope of 74 mV dec . A systematic contrast of the electrocatalytic performances for the OER increase in the order: 1D Co O <2D Co O <1D CoSe <2D CoSe . This work provides fundamental insights into the morphology-performance relationships of both Co O and CoSe , which were synthesized through the same approach, providing a solid guide for designing OER catalysts.