Electrochemical Hydrogen Compression: Efficient Pressurization Concept Derived from an Energetic Evaluation

Abstract

Electrochemical hydrogen compression is a potentially high efficient, low-maintenance and silent technology to produce high pressure hydrogen. A new pressure concept with increased compression efficiency, termed intermediate differential pressure polymer electrolyte water electrolysis is proposed. With slightly pressurized oxygen and a much higher hydrogen pressure, this pressure concept profits from the advantages of the lower gas crossover of differential (only hydrogen compressed) pressure water electrolysis and the improved oxygen evolution reaction kinetics with increasing pressure of balanced pressure operation. Data for gas pressures up to 100 MPa is modeled, based on experimental results up to 5 MPa, of the three pressure concepts and validated with literature data up to 70 MPa. While differential pressure electrolyzer operation, following ideal isothermal compression, can be more efficient than today's best mechanical compressors up to 40 MPa, the intermediate pressure concept shows higher compression efficiency up to 90 MPa.

Improving the Efficiency of PEM Electrolyzers through Membrane-Specific Pressure Optimization

“…It was shown by Grigoriev et al that for high current densities, the cell voltage can be reduced by increasing the pressure, which is in contradiction to the Nernst equation [32]. This result was approved by Bernt et al [33] and was shown by Suermann et al for the balance pressure mode [21]. This finding relates to enhanced reaction kinetics, which makes j 0 a function of pressure.…”

“…In this case, four mechanical compression steps can be saved when the storage pressure is 100 bar; the membrane thickness is not given in this work. However, Suermann et al concluded that the use of a Nafion 117 membrane allows a reduction in permeation to low levels, and, hence, a cathode pressure of 100 bar [21]. Moreover, several other studies have been conducted that focus on improving PEM electrolysis system operation and efficiency [22][23][24][25][26].…”

Local Current Density and Electrochemical Impedance Measurements within 50 cm Single-Channel PEM Electrolysis Cell

“…These characteristic drops of the CDD at the channel outlet are also documented in literature for PEMFCs 16,17 and for electrochemical hydrogen compression. 18 In fuel cells the educt starvation at the outlet of the cell builds up a reaction front, which moves toward the inlet, when the amount of educt is further reduced. Mass transport limitation of oxygen in a PEMFC is considered as the main issue for that phenomenon.…”

The synthesis of a Zirfon‐type porous separator with reduced gas crossover for alkaline electrolyzer

“…However, AWEs exhibit poor performance in terms of a slow ramping rate, low partial load range, and low operating pressure compared with proton exchange membrane (PEM) electrolyzers, mainly due to the use of liquid electrolytes, such as KOH, and gas crossover through porous separators . Researches on alkaline anion‐exchange separators have been actively carried out to overcome these problems, but their performance and stability are still much lower than those of their acidic separators . Commercial AWEs employ porous separators such as asbestos, fabric of polyphenylene sulfide (PPS), and composite materials.…”

“…9,10 Researches on alkaline anion-exchange separators have been actively carried out to overcome these problems, but their performance and stability are still much lower than those of their acidic separators. 11,12 Commercial AWEs employ porous separators such as asbestos, fabric of polyphenylene sulfide (PPS), and composite materials. Asbestos is no longer used as a separator due to its carcinogenic properties and its instability at high temperature.…”