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A series of new salts with a small ether-functionalised trimethylammonium cation are synthesised and characterised to probe their unique structure–property relationships.

Shuttling protons in ammonia synthesis An electrochemical route to ammonia could substantially lower the greenhouse gas emissions associated with the current thermal Haber-Bosch process. One relatively promising option under study involves reductive formation of lithium nitride, which can be protonated to ammonia. However, the ethanol used to date as a local proton source in these studies may degrade under the reaction conditions. Suryanto et al. report the use of a tetraalkyl phosphonium salt in place of ethanol (see the Perspective by Westhead et al. ). This cation can stably undergo deprotonation–reprotonation cycles and, as an added benefit, it enhances the ionic conductivity of the medium. Science , abg2371, this issue p. 1187 ; see also abi8329, p. 1149

There is an urgent need for more efficient technologies to mitigate climate change, such as the separation and capture of CO2 from flue gas. This work explores light gas separation based on a series of novel Organic Ionic Plastic Crystals (OIPCs) and polymer composites with the advantage of competitive and tuneable performance. Five OIPCs based on the bis(fluorosulfonyl)imide ([FSI]−) anion were selected and co-cast with poly(vinylidene fluoride) (PVDF) or poly(ethylene oxide) (PEO). Their gas transport properties were evaluated at temperatures where some of the OIPCs exist in different thermal phases. It was found that the nature of the polymer has a strong impact on separation performance, with PVDF demonstrating more advantageous properties than PEO. However, every OIPC has a different response to a given polymer type and ratio. A remarkable increase in permeability, from ∼100 to ∼360 Barrer, was achieved for triethyl(methyl)phosphonium bis(fluorosulfonyl)imide ([P1222][FSI])-based composites upon increasing the PVDF ratio, while preserving high selectivity (α ≈ 29). Additionally, large changes in separation performance were observed in OIPCs that undergo a solid–solid phase transition. A shift from phase II to phase I resulted in a dramatic increase in permeability (from ∼12 to ∼500 Barrer) for hexamethylguanidinium bis(fluorosulfonyl)imide ([HMG][FSI])-based composites. Analysis of the relationship between structure and transport properties of the different composites reveals insights into the effect of different OIPC and polymer chemistries and points to promising new directions in the development of highly permeable and selective gas separation membranes.

The development of safer electrolytes is critical for the advancement of electrochemical energy storage applications. Ionic Liquids (ILs) and Organic Ionic Plastic Crystals (OIPCs) are attractive choices as electrolytes due to their high thermal stabilities and intrinsic ionic conductivities. However, fundamental understanding of the impact of cation and anion choice, to form ILs or OIPCs, is still lacking, particularly with regard to how this can affect the electrolyte properties. In this work, we explore the synthesis and characterisation of several oxazolidinium-based salts to understand the effect of the ether functional group in the cation ring. Specifically, we investigate the 3,3-dimethyloxazolidinium ([C1moxa]+) cation, paired with dicyanamide ([DCA]−), bis(fluorosulfonyl)imide ([FSI]−), bis(trifluoromethanesulfonyl)imide ([TFSI]−), tetrafluoroborate ([BF4]−) and hexafluorophosphate ([PF6]−) anions. In addition to investigating the influence of the anion, the effect of changing the cation side chain is examined with 3-ethyl-3-methyloxazolidinium bis(fluorosulfonyl)imide ([C2moxa][FSI]). Studies of thermal behaviour revealed that these oxazolidinium-based salts can be highly disordered and exhibit wide phase I temperature ranges. The transport properties of the salts were determined by examining the ionic conductivity, ion dynamics using solid-state Nuclear Magnetic Resonance (NMR) analysis, and the free volume through Positron Annihilation Spectroscopy (PALS). It was found that oxazolidinium-based salts exhibit faster ion transport than the equivalent pyrrolidinium-based salts, which is consistent with the larger free volume. Hence, oxazolidinium-based salts demonstrate scope as promising electrolytes for battery applications due to their high ionic conductivity and good thermal and electrochemical stability.

The implementation of next-generation batteries requires the development of safe, compatible electrolytes that are stable and do not cause safety problems. The difluoro(oxalato)borate ([DFOB]

Electrochemical ammonia synthesis at ambient temperature and pressure shows promise as a route to a carbon-free chemical fuel for renewable energy transportation and storage. However, before this p...

Renewable energy-driven ammonia electrosynthesis by N2 reduction reaction (NRR) at ambient conditions is vital for sustainability of both the global population and energy demand. However, NRR under ambient conditions to date has been plagued with a low yield rate and selectivity (

The reduction of 2,4,6-trinitrotoluene (TNT) has been studied in eight room temperature ionic liquids (RTILs) on a gold (Au) microdisk electrode and a Au thin film electrode (TFE). Three reduction peaks were observed in all RTILs, corresponding to the reductions of each of the three nitro groups in the TNT structure. TNT was the easiest to reduce in imidazolium RTILs, followed by pyrrolidinium and then tetraalkylphosphonium. Diffusion coefficients (D) and electron counts (n) were calculated from potential-step chronoamperometry on the first reduction peak. D’s ranged from 0.7 × 10–11 to 4.1 × 10–11 m2 s–1, and a plot of D against the inverse of viscosity was linear, indicating that the Stokes–Einstein relation holds well for TNT in RTILs. The electron count was one in most RTILs—in stark contrast to the widely accepted six-electron reduction in protic solvents. An electrogenerated red solid was formed after the first reduction peak, believed to be an azo (or azoxy) compound formed by dimerization of two T...

The electrochemical behavior of methylamine gas in several room temperature ionic liquids (RTILs), (C2mim)(NTf2), (C4mim)(NTf2), (C6mim)(FAP), (C4mpyrr)(NTf2), (C4mim)(BF4), and (C4mim)(PF6), has been investigated on a Pt microelectrode using cyclic voltammetry. A broad oxidation wave at approximately 3 V, two reduction peaks, and another oxidation peak were observed. A complicated mechanism is predicted based on the voltammetry obtained, with ammonia gas as a likely byproduct. The currents obtained suggest that methylamine has a high solubility in RTILs, which is important for gas-sensing applications. The analytical utility of methylamine was then studied in (C4mpyrr)(NTf2) and (C2mim)- (NTf2). A linear calibration graph with an R 2 value of 0.99 and limits of detection of 33 and 34 ppm were obtained, respectively, suggesting that RTILs are favorable nonvolatile solvents for the electrochemical detection of highly toxic methylamine gas.