Investigating proton exchange membrane water electrolyzers (PEMWE) performance losses through the galvanostatic intermittent titration technique (GITT) for electrolyzers
Fausto N Pasmay, Shawn Litster
Abstract
This study introduces a novel electrochemical technique to characterize the transient development of overpotentials in PEMWEs based on GITT. The basis of the technique is high temporal resolution characterization of voltage increase during galvanostatic (i.e., constant current) titrations. The time-scales of voltage increases can be correlated to electrochemical and transport time-scales to identify individual overpotential contributions to the cell voltage. Herein, we focus on evaluating the overpotentials due to mass transport losses, specifically the impact of liquid water displaced by evolved oxygen. The study is motivated by prior work indicating that there is a significant mass transport overpotential, as estimated from voltage breakdown analysis using high-frequency resistance (HFR) and Tafel analysis. Through time-scale analysis, we find negligible mass transport losses evolve over a time scale longer than that of electric double layer (EDL) charging time. We propose near instantaneous phenomena are responsible for most of the additional overpotentials, which can include ohmic losses in the electrode that are not captured by the high-frequency resistance and ohmic overpotential. • New electrochemical diagnostic for PEMWEs using GITT for evaluating transient overpotentials. • Time-scale analysis to identify phenomena responsible for generating overpotentials. • No significant overpotential development occurring at time scales greater than that of electric double-layer charging. • Voltage losses at high current densities are related to uncharacterized resistances not related to pore-phase mass transport.