Proton transport in choline dihydrogen phosphate/H3PO4 mixtures

Abstract

Mixtures of the plastic crystal material choline dihydrogen phosphate [Choline][DHP] and phosphoric acid, from 4.5 mol% to 18 mol% H(3)PO(4), were investigated and shown to have significantly higher proton conductivity compared to the pure [Choline][DHP]. This was particularly evident from the electrochemical hydrogen reduction reaction and the proton NMR diffusion measurements, in addition to ionic conductivity measured from the impedance spectroscopy. The ionic conductivity was observed to increase by more than an order of magnitude in phase I (i.e. the highest temperature solid phase in [Choline][DHP]) reaching up to 10(-2) S cm(-1). The multinuclear NMR spectroscopy data suggest that, at least on the timescale of the NMR measurement, the H(+) cations and [DHP] anions are equivalent in both phases. The pulsed field gradient NMR diffusion measurements of the 18 mol% acid sample indicate that all three ions are mobile, however the H(+) diffusion coefficient is an order of magnitude higher than for the [Choline] cation or the [DHP] anion, and therefore conduction in these materials is dominated by proton conductivity. The thermal stability, as measured by TGA, is unaffected with increasing acid additions and remains high; i.e. no significant mass loss below 200 °C.

Application of the Kwei equation to model the Tg behavior of binary blends of sugars and salts

“…Table 1 also gives the values of parameters in the G-T and Kwei equation. Note that the data point for neat CDHP was not measured in this study but instead given by reference [11]. Here we consider the anhydroustris or citrate buffer as a single component in the aforementioned equations as in the original study [12].…”

“…The synthesis of CDHP was performed according to methods previously reported in the literature [11]. Briefly, it was synthesized by a slow addition of an aqueous solution (85 wt%) of phosphoric acid (5.7 g) to 20 wt% aqueous choline hydroxide solution (30.1 g) in an ice bath with stirring for 2 hours at room temperature.…”

Interaction of choline salts with artificial biological membranes: DSC studies elucidating cellular interactions

“…2-hydroxyethyl(trimethyl)azanium dihydrogen phosphate ( CDHP , choline dihydrogen phosphate), melting point = 195 °C [15] 1 ,…”

A study of phase behavior and conductivity of mixtures of the organic ionic plastic crystal N-methyl-N-methyl-pyrrolidinium dicyanamide with sodium dicyanamide

“…OIPC materials have wide applications in batteries, fuel cells, photoelectrochemical cells and also super capacitors because they are highly conductive in both solid and liquid states [6,7,[10][11][12][13][14][15][16][17][18][19][20]. Plastic crystals are typically ordered crystalline materials at lower temperatures, which undergo one or more solid-solid phase transitions at higher temperatures.…”

“…[1,2,4,8,[11][12][13][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], were investigated mainly for electrolytes in batteries [38,39] and fuel cells [13] at ambient temperatures. In these materials, one of the most important properties is the significant transport of the target ion, such as the H + ion in fuel cells and Li + ion in Li batteries.…”