Electrochemical Behaviour of Hydrogen in Low-Viscosity Phosphonium Ionic Liquids

Abstract

The electrochemical and diffusive properties of hydrogen in low-viscosity phosphonium ionic liquids were investigated by the electrochemical methods such as cyclic voltammetry and chronoamperometry. The hydrogen redox reactions were concluded to be a quasi-reversible system in phosphonium-based ionic liquids. The diffusion coefficients of hydrogen in these ionic liquids were of the order of 10 −10 m 2 s −1 at 25 • C. Additionally, the obtained activation energy of the diffusion process for hydrogen was 11.2 -15.9 kJ mol −1 estimated from the temperature dependence of the diffusion coefficients.A new type of proton conducting medium such as triethylphosphonium bis(trifluoromethylsulfonyl)amide was synthesized by the neutralization reaction, because the trialkylphosphine-based ionic liquids with good stability at higher temperature and high conductivity were appropriate candidates. This proton conducting membrane containing the ionic liquids with trialkylphosphine-based cations and the polyvinylidenefluoride-co-hexafluoropropylene has been fabricated in the present study. The proton conducting membrane exhibits relatively high ionic conductivity along with good mechanical stability.

Molecular Insight into the Ionic Conduction of Quaternary Ammonium and Phosphonium Cation-Based Ionic Liquids Using Dielectric and Spectroscopy Analyses

“…Moreover, the diffusion rate of P2228-TFSA was higher than that of N2228-TFSA, and a lower diffusion rate is often associated with a higher viscosity. 48 According to Griffin et al, 33 the difference in ion transport properties between N2228-TFSA and P2228-TFSA can be explained in terms of the glass transition temperatures of these ILs (inset of Figure 4b). The σ dc values of N4441-TFSA and P4441-TFSA followed similar VFT-type temperature dependences (Figure S2).…”

“…According to the molar conductivity (Λ) plot (Figure b), the σ dc value of P2228-TFSA was higher than that of N2228-TFSA because the phosphonium cation diffused faster than the quaternary ammonium cation. Moreover, the diffusion rate of P2228-TFSA was higher than that of N2228-TFSA, and a lower diffusion rate is often associated with a higher viscosity . According to Griffin et al, the difference in ion transport properties between N2228-TFSA and P2228-TFSA can be explained in terms of the glass transition temperatures of these ILs (inset of Figure b).…”

Phosphonium polyelectrolytes: influence of diphosphine spacer on layer‐by‐layer assembly with anionic conjugated polymers

“…Phosphonium polyelectrolytes (Scheme ) have already demonstrated utility as antibacterial films for surface modification, as nonviral vectors for the delivery of biological entities and as the supporting element in solid‐supported synthesis and phase‐transfer catalysis . Phosphonium polymers also have among the best combination of stability and ion conductivity required for use in hydroxide‐transporting alkaline fuel cells, currently a hotly pursued area in both academic and industrial laboratories . Phosphonium salts are especially attractive because they can often be readily prepared under mild conditions and unlike phosphines they have good air stability.…”