Effect of Thiourea on the Kinetics of the Hydrogen Evolution Reaction at Iron and the Transport of Hydrogen through a Steel Membrane in Solutions of C2H4(OH)2-H2O-HCl

Abstract

The effect of thiourea (0.5-10 mM) on the kinetics of the hydrogen evolution reaction (HER) at iron and the hydrogen transport through a steel membrane out of ethylene glycol (containing 2 and 10 wt % H 2 O) and aqueous solutions containing HCl (0.1-0.99 M) with a constant ionic strength equal to unity is studied in parallel experiments. The presence of 0.5 mM of thiourea in the solutions raises the overvoltage of hydrogen evolution, while a subsequent increase in its concentration does not effect the HER kinetics. The dependence of the flux of hydrogen diffusion through the membrane on the thiourea content passes through a maximum.

Hydrogen diffusion through the steel membrane in conditions of its anodic polarization

“…With increasing the initial water concentration up to 2 wt% both the solvated forms of the protons (C 2 H 4 (OH) 2 The hydrogen overvoltage increase was determined by the independent and direct polarization measurements with use of the equilibrium hydrogen electrode in the same solution as a reference electrode [11,17,18].…”

“…At the considerable anodic polarization, when the cathodic process rate diminishes tenfold and more, i H ceases to depend on the potential of the entrance membrane side in the sufficiently wide range of the anodic potentials [10]. Such a picture, in particular, is characteristic for the acidic alcohol (ethylene glycol, ethanol) solutions and the water-alcohol media where the chemical dissolution of iron proceeds at the essential rate [11]. The chemical dissolution of metal is a process when the redox reaction proceeds for the alone act and the metal ionization rate i ch measured by the independent method does not depend on the electrode potential in both the cathodic and wide anodic potential range.…”

Development of the Iron Electrode for Utility Scale Energy Storage

“…show that thiourea increases the overvoltage of the HER on iron, albeit in aqueous solutions of ethylene glycol [121].…”

“…It is proposed that these performance improvements are due to formation of a catalytic lithium-iron-oxide intermediate [118]. Further performance gains are possible through use of thiourea, which has been shown previously to raise the overvoltage of the hydrogen evolution reaction [121]- [123].…”

“…Open Circuit Potential (OCP) studies were also performed and the author mentions negative results but does not elaborate why or investigate in terms of passivation [77]. This is unfortunate as the authors note that thiourea has been used successfully to alter hydrogen evolution kinetics on other materials and more research on its interactions with the iron electrode would be of value [121]- [123]. Vigdorovich et al…”