CO2 Electroreduction in Ionic Liquids

CO2 electroreduction is among the most promising approaches used to transform this green-house gas into useful fuels and chemicals. Ionic liquids (ILs) have already proved to be the adequate media for CO2 dissolution, activation, and stabilization of radical and ionic electrochemical active species in aqueous solutions. In general, IL electrolytes reduce the overpotential, increase the current density, and allow for the modulation of solution pH, driving product selectivity. However, little is known about the main role of these salts in the CO2 reduction process the assumption that ILs form solvent-separated ions. However, most of the ILs in solution are better described as anisotropic fluids and display properties of an extended cooperative network of supramolecular species. That strongly reflects their mesoscopic and nanoscopic organization, inducing different processes in CO2 reduction compared to those observed in classical electrolyte solutions. The major aspects concerning the relationship between the structural organization of ILs and the electrochemical reduction of CO2 will be critically discussed considering selected recent examples

Efficient Electrocatalytic CO2 Reduction Driven by Ionic Liquid Buffer‐Like Solutions

We show here that electrocatalysis of CO2 reduction in aqueous electrolytes containing the ionic liquid (IL) 1-n-butyl-2,3dimethylimidazolium acetate ([BMMIm][OAc]) and dimethyl sulfoxide (DMSO) proceeds at low overpotentials (−0.9 V vs. Ag/AgCl) at commercially-available Au electrodes, and with high selectivity for CO production (58% faradaic efficiency at –1.6 V vs Ag/AgCl). 0.43 mol of CO2 per mol of IL can be absorbed into the electrolyte at atmospheric pressure, forming bicarbonate and providing a constant supply of dissolved CO2 to the surface of the electrode. We also show that electrocatalysis of CO2 reduction in the electrolyte is facilitated by stabilization of CO2 radical anions by the imidazolium cations of the IL and buffer-like effects with bicarbonate

Hybrid tantalum oxide nanoparticles from the hydrolysis of imidazolium tantalate ionic liquids: efficient catalysts for hydrogen generation from ethanol/water solutions

The reaction of equimolar amounts of 1-n-butyl-3-methylimidazolium chloride (BMI·Cl) or 1-n-decyl-3-methylimidazolium chloride (DMI·Cl) with TaCl5 affords imidazolium tantalate ionic liquids (ILs) BMI·TaCl61 and DMI·TaCl62. The hydrolysis of ILs 1 and 2 yields hybrid-like tantalum oxide nanoparticles (NPs) with size distribution dependent on the nature of the IL used (3.8–22 nm from IL 1 and 1.5–6 nm from 2). A significant aggregation/agglomeration of the particles was observed after the removal of the IL content of the hybrid material by calcination, forming predominantly large particles (mainly bulk tantalum oxides). These new hybrid-like Ta2O5/IL NPs are highly active photocatalyst nanomaterials for hydrogen production by reforming of ethanol at ambient temperature. Hydrogen evolution rates up to 7.2 mmol H2 g−1 h−1 and high apparent quantum yields up to 17% were measured. The hybrid-like Ta2O5/IL NPs sputtered-decorated with ultra-small Pt NPs (1.0 ± 0.3 nm) as co-catalysts reached activities leading to even higher hydrogen production (9.2 H2 mmol g−1 h−1; apparent quantum yield of 22%). The calcined materials (with or without Pt NPs) showed much lower photocatalytic activity under the same reaction conditions (up to 2.8 mmol g−1 of H2). The remarkable activity of the hybrid-like Ta2O5/IL NPs may be related to the presence of the remaining IL that provides hydrophilic regions, facilitating the approach of polar molecules (water and alcohol) to the semiconductor active photocatalytic sites

Growth of TiO2 nanotube arrays with simultaneous Au nanoparticles impregnation: photocatalysts for hydrogen production

Um novo método para a fabricação de nanotubos (NTs) de TiO2 organizados e impregnados com nanopartículas (NPs) de ouro foi desenvolvido, e as propriedades estruturais, morfológicas e ópticas dos NTs obtidos foram investigadas. Os arranjos de NTs de TiO2 foram crescidos pela oxidação anódica de Ti metálico utilizando soluções eletrolíticas contendo íons fluoreto e NPs de Au. As estruturas resultantes foram caracterizadas por espectrometria de retroespalhamento Rutherford (RBS), difratometria de raios X com incidência rasante (GIXRD), microscopias eletrônicas de transmissão (TEM) e de varredura (SEM) e espectroscopia UV-Vis. Tanto os arranjos de NTs sem Au quanto os impregnados com Au mostraram atividade fotocatalítica boa e estável na geração de hidrogênio a partir de misturas água/metanol. Os nanotubos de TiO2 contendo Au foram mais ativos na fotogeração de hidrogênio do que os NTs de TiO2 sem Au.A novel method for the fabrication of TiO2 nanotubes (NTs) impregnated with gold nanoparticles (NPs) is reported. TiO2 NT arrays were grown by anodic oxidation of Ti metal using fluoride electrolytes containing Au NPs. Resulting structures were characterized by Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffractometry (GIXRD), transmission and scanning electron microscopy (SEM and TEM) and UV-Vis spectroscopy. Au-free and Au-impregnated TiO2 NT arrays showed good and stable photocatalytic activity for hydrogen generation from water/methanol solutions. Au-containing TiO2 NTs presented higher hydrogen photogeneration activity than Au-free TiO2 NTs

Remote-controlled experiments with cloud chemistry

Developing cleaner chemical processes often involves sophisticated flow-chemistry equipment that is not available in many economically developing countries. For reactions where it is the data that are important rather than the physical product, the networking of chemists across the internet to allow remote experimentation offers a viable solution to this problem

Bimetallic RuPd nanoparticles in ionic liquids: selective catalysts for the hydrogenation of aromatic compounds

Bimetallic RuPd nanoparticles (NPs) immobilized in ionic liquids (ILs) were shown to be a highly active medium for the selective hydrogenation of benzene and phenol under mild conditions (4 bar H-2, 60 degrees C) in a biphasic system (n-heptane/IL). The equimolar combination of Ru and Pd into a bimetallic particle generated a synergistic catalyst that allowed the selective production of cyclohexane (>99% selectivity, 94% conversion) and cyclohexanol (99% selectivity, >98% conversion) from the reduction of benzene and phenol, respectively. Moreover, the catalytic results revealed that the activity and selectivity are dependent on the Ru : Pd ratio into the bimetallic NPs

Challenging thermodynamics: hydrogenation of benzene to 1,3- cyclohexadiene by Ru@Pt nanoparticles

Since the earliest reports on catalytic benzene hydrogenation, 1,3-cyclohexadiene and cyclohexene have been proposed as key intermediates. However, the former has never been obtained with remarkable selectivity. Herein we report the first partial hydrogenation of benzene towards 1,3 cyclohexadiene under mild conditions in a catalytic biphasic system consisting of Ru@Pt nanoparticles (NPs) in ionic liquid (IL). The tandem reduction of [Ru(COD)(2-methylallyl)2] (COD = 1,5 cyclooctadiene) followed by decomposition of [Pt2(dba)3] (dba = dibenzylideneacetone) in 1-nbutyl- 3 methylimidazolium hexafluorophosphate (BMI.PF6) IL under hydrogen affords core-shell Ru@Pt NPs of 2.9 ± 0.2 nm. The hydrogenation of benzene (60 ºC, 6 bar of H2) dissolved in nheptane by these bimetallic NPs in BMI.PF6 affords 1,3- cyclohexadiene in unprecedented 21% selectivity at 5% benzene conversion. On opposition, almost no 1,3-cyclohexadiene was observed using monometallic Pt(0) or Ru(0) NPs under the same reaction conditions and benzene conversions. The study reveals that the selectivity is related to synergetic effects of the bimetallic composition of the catalyst material as well as the performance under biphasic reaction conditions. It is proposed that colloidal metal catalysts in ILs and under multiphase conditions (“dynamic asymmetric mixture”) can operate far from the thermodynamic equilibrium akin to chemically active membranes

Tunable Ionic Control of Polymeric Films for Inkjet Based 3D Printing.

Inkjet printing is a powerful additive manufacturing (AM) technique to generate advanced and complex geometries. However, requirements of low viscosity and surface tension are limiting the range of functional inks available, thus hindering the development of novel applications and devices. Here, we report a method to synthesise materials derived from highly viscous or even solid monomers in a simple, flexible fashion and with the potential to be integrated in the printing process. Polymerisable ionic liquids (PILs) have been employed as a proof of principle due to the broad range of properties available upon fine tuning of the anion/cation pair and the high viscosity of the monomers. The method consists of the deposition and polymerization of a PIL precursor, followed sequentially by quaternisation and anion metathesis of the films. The fine control over the mechanical and superficial properties of inkjet printable polymeric films of neutral and cationic nature by post-polymerization reactions is demonstrated for the first time. A family of different polycationic materials has been generated by modification of cross-linked copolymers of butyl acrylate and vinyl imidazole with liquid solutions of functional reagents. The variation in the mechanical, thermal and surface properties of the films demonstrates the success of this approach. The same concept has been applied to a modified formulation, designed for optimal inkjet printing. This work will pave the way for a broad range of applications of inkjet printing, with a plethora of anion-cation combinations characteristic of PILs, thus enormously broadening the range of applications available in additive manufacturing