The Standard Potential of the Bromine Electrode

Inhibition of hydrogen oxidation by HBr and Br2

“…Consequently, ATcT currently produces an enthalpy of formation of HBr (-35.85±0.15 kJ mol −1 at 298.15 K) that is higher (less negative) than the value assigned by CODATA by an amount that -while not large in absolute terms -exceeds substantially the combined uncertainties, leading to the conclusion that the aqueous thermochemical route selected by CODATA contains a hidden cumulative systematic bias that is larger than their declared uncertainty. It should be stressed here that while the current ATcT value for HBr relies heavily on spectroscopic data, it is, at the same time, still entirely consistent (within the respective uncertainties) with the relevant calorimetric [54,55] and aqueous [56][57][58][59][60][61][62][63][64] thermochemical measurements.…”

High energy density electrolytes for H2/Br2redox flow batteries, their polybromide composition and influence on battery cycling limits

“…Values for K 3 between 16.0 and 18.08 L mol À1 at 25 C are known in literature. 20,[26][27][28][29][30][31][33][34][35] For K 5 , values between 19.45 L 2 mol À2 and 40 L 2 mol À2 are reported in literature. 20,29,31,[33][34][35] Both equilibria are shied to the polybromide side and reduce free uncomplexed Br 2 in the electrolyte.…”

“…Bromine itself exhibits a limited solubility in pure water at around 0.214 mol L À1 at q ¼ 25 C. [20][21][22] The hydrolysis reaction of Br 2 (ref. [23][24][25][26] is supressed in HBr for concentrations of 0.001 M or higher.…”

“…[27][28][29][30][31] Solubility of Br 2 increases signicantly in aqueous bromide solutions like hydrobromic acid. Soluble polybromide complexes (eqn (2) and ( 3)), such as tribromide (Br 3 À ) or pentabromide ions (Br 5 À ) 20,28,29 are formed in an equilibrium reaction between Br 2 , bromide and the respective polybromide:…”

“…The equilibrium constants of the polybromide formation (K n ) are determined according to the law of mass action, shown in eqn (4) and (5). 20,[26][27][28][29][30][31][33][34][35]…”