Material development and process optimization for gas-phase hydrogen chloride electrolysis with oxygen depolarized cathode

Abstract

In the present contribution, the gas-phase electrolysis of hydrogen chloride in a polymer electrolyte membrane electrolyzer was investigated in detail. Different graphite-based bipolar plate materials were tested for this purpose with the graphite-polymer compound BMA5 being the most suitable among the tested materials regarding porosity as well as corrosion stability and electrical conductivity. Investigation of the membrane pretreatment process revealed that the best results are obtained with sulfuric acid as proton donor. Furthermore, an optimized electrocatalyst distribution with asymmetrical loadings on anode and cathode was found to result in reduced cell voltage at considerably decreased overall noble metal content. Finally, the influence of the cathode gas humidification on the overall cell voltage as well as on the individual anode and cathode potentials, measured with reference electrodes, was determined. It could be shown that a relative humidity ranging from 60 to 80 % is optimal for operation of the gas-phase hydrogen chloride electrolyzer.

Energy‐Efficient Gas‐Phase Electrolysis of Hydrogen Chloride

“…b) Explosion view of a gas-phase reactor for the hydrogen chloride electrolysis consisting of: (1) one MEA, (2) two GDLs, (3) two bipolar plates, (4) two end plates, and (5) the gaskets. Reprinted from [19] with permission from Springer Nature. of carbon cloth coated with polytetrafluoroethylene (PTFE) in a first step and with a mixture of Ketjenblack and PTFE in a second step leading to a three-dimensional network consisting of hydrophilic and hydrophobic parts with a microporous structure.…”

“…The overall PTFE content in the GDL was 20 wt %. In between the two GDLs of the anode and cathode compartment is the membrane electrode assembly (MEA), which consists of a Nafion 117 membrane between the CCL and ACL [13,19]. The catalyst layer consisted of a commercial catalyst from BASF with 60 wt % Pt/C and Nafion [19].…”

“…In between the two GDLs of the anode and cathode compartment is the membrane electrode assembly (MEA), which consists of a Nafion 117 membrane between the CCL and ACL [13,19]. The catalyst layer consisted of a commercial catalyst from BASF with 60 wt % Pt/C and Nafion [19]. The measurements were performed at two different catalyst loadings: In the first case, 1 mg cm -2 Pt and 1 mg cm -2 Nafion were chosen on both the anode as well as the cathode side (referred to as standard loading) and secondly, 0.5 mg cm -2 Pt with 1 mg cm -2 Nafion was chosen for the anode and 0.5 mg cm -2 Pt with 0.5 mg cm -2 Nafion for the cathode, denoted as optimized loading as explained in Sect.…”

“…The measurements were performed at two different catalyst loadings: In the first case, 1 mg cm -2 Pt and 1 mg cm -2 Nafion were chosen on both the anode as well as the cathode side (referred to as standard loading) and secondly, 0.5 mg cm -2 Pt with 1 mg cm -2 Nafion was chosen for the anode and 0.5 mg cm -2 Pt with 0.5 mg cm -2 Nafion for the cathode, denoted as optimized loading as explained in Sect. 2.4 [19,20]. The employed membrane consisted of Nafion 117 and was pretreated with deionized water, hydrogen peroxide and 1 M H 2 SO 4 at elevated temperatures [13,19].…”

The modeling gap: What we are missing between molecular dynamics of electrode reactions and simulation of battery packs

“…Turek went a step further on the dimensional scale when reporting on recent progress in modeling and material development for oxygen reducing electrodes in the chlor-alkaline electrolysis [34,35]]. Although these electrodes are basically porous gas-fed electrodes similar to those used in phosphoric acid fuel cells methodology and results hardly fit to electrodes in supercapacitors and alkali ion batteries.…”