Feasibility of Hydrogen Compression in an Electrochemical System: Focus on Water Transport Mechanisms

Abstract

AbstractIn this study, the behavior of an electrochemical hydrogen compressor (EHC) able to compress hydrogen up to 32 bar was investigated. The current density distribution along the EHC was measured using a segmented cell. It was found to decrease from 0.75 A cm−2 to 0.65 A cm−2 along the EHC when using Nafion 117 and when high relative humidity hydrogen was fed to the EHC (at 0.66 A cm−2 and 0.36 V). This drop corresponded to a decrease of the relative humidity of the hydrogen flow from 90 to 55% along the gas channels at the anode side, evidencing the local dehydration of the PEM due to the unbalanced water transport across the membrane. As a consequence, the membrane resistance increased, thus a higher voltage had to be supplied to the EHC in order to maintain good performances, decreasing the overall efficiency. On the other hand, unstable operating conditions were observed when using hydrogen with a low relative humidity.A pseudo‐2D model was developed along with experimental studies to estimate the physical parameters enhancing the efficiency of the EHC. A higher efficiency was obtained when using a thinner membrane than Nafion 117 (53% vs. 37%, at 60 °C and 0.66 A cm−2).