TY - JOUR

T1 - Hydrogen Crossover in PEM and Alkaline Water Electrolysis

T2 - Mechanisms, Direct Comparison and Mitigation Strategies

AU - Trinke, P.

AU - Haug, P.

AU - Brauns, J.

AU - Bensmann, B.

AU - Hanke-Rauschenbach, R.

AU - Turek, Thomas

N1 - Funding information: The authors gratefully acknowledge the financial support by the Federal Ministry of Education and Research of Germany in the frame-work of PowerMEE (project number 03SF0536B) and the DFG in the framework of the projects INST 189/182-1 FUGG and TU 89/18-1. The authors gratefully acknowledge the financial support by the FederalMinistry of Education and Research of Germany in the framework of PowerMEE (project number 03SF0536B) and the DFG in the framework of the projects INST 189/182-1 FUGG and TU 89/18-1.

PY - 2018/5/16

Y1 - 2018/5/16

N2 - This study provides a direct comparison of hydrogen crossover in PEM (Nafion 117) and alkaline water electrolysis (Zirfon) at a temperature of 60?C applying state-of-the-art separating unit materials. To this end, occurring crossover mechanisms are described first, before experimental data of the anodic hydrogen content are shown in dependence of current density, system pressure and process management strategy. The results suggest that permeation in PEM electrolyzers is mainly governed by diffusion due to a supersaturated concentration of dissolved hydrogen within the catalyst layer, showing a share of 98% of the total permeation flux at 1Acm-2 and atmospheric pressure. Permeation in alkaline electrolyzers also exhibits a significant influence of supersaturation, but the overall crossover is mainly influenced by mixing the electrolyte cycles, which makes up a share of 90% at 0.7Acm-2 and 1 bar. Generally it becomes evident that hydrogen permeation across the separating unit is more than one order of magnitude smaller in alkaline electrolysis, which is mainly a consequence of the significantly lower hydrogen solubility in concentrated KOH electrolyte. Finally, this study concludes with an assessment of the impact of separating unit thickness and provides mitigation strategies to reduce hydrogen crossover.

AB - This study provides a direct comparison of hydrogen crossover in PEM (Nafion 117) and alkaline water electrolysis (Zirfon) at a temperature of 60?C applying state-of-the-art separating unit materials. To this end, occurring crossover mechanisms are described first, before experimental data of the anodic hydrogen content are shown in dependence of current density, system pressure and process management strategy. The results suggest that permeation in PEM electrolyzers is mainly governed by diffusion due to a supersaturated concentration of dissolved hydrogen within the catalyst layer, showing a share of 98% of the total permeation flux at 1Acm-2 and atmospheric pressure. Permeation in alkaline electrolyzers also exhibits a significant influence of supersaturation, but the overall crossover is mainly influenced by mixing the electrolyte cycles, which makes up a share of 90% at 0.7Acm-2 and 1 bar. Generally it becomes evident that hydrogen permeation across the separating unit is more than one order of magnitude smaller in alkaline electrolysis, which is mainly a consequence of the significantly lower hydrogen solubility in concentrated KOH electrolyte. Finally, this study concludes with an assessment of the impact of separating unit thickness and provides mitigation strategies to reduce hydrogen crossover.

UR - http://www.scopus.com/inward/record.url?scp=85053776451&partnerID=8YFLogxK

U2 - 10.1149/2.0541807jes

DO - 10.1149/2.0541807jes

M3 - Article

AN - SCOPUS:85053776451

VL - 165

SP - F502-F513

JO - Journal of the Electrochemical Society

JF - Journal of the Electrochemical Society

SN - 0013-4651

IS - 7

ER -