Investigation of the correlation effects of catalyst loading and ionomer content in an anode electrode on the performance of polymer electrode membrane water electrolysis

Abstract

In this study, the correlation effect of catalyst loading (Lc) and ionomer content (Ciono) on the performance of polymer electrolyte membrane water electrolysis (PEMWE) is investigated. Sixteen membrane electrode assemblies are constructed and electrochemically evaluated using a cross-combination of two factors. Although the coupling of the two factors does not significantly affect the performance at a low working voltage, the effect is dominant at a high working voltage. Based on the establishment of correlations between the changes in the contributing factors (including the ionomer fraction, thickness, and porosity) caused by variations in the two factors, the effects on the kinetic, ohmic, and mass transfer overpotential are estimated and analyzed. Since the Ciono and Lc simultaneously affect the porosity, the required Ciono for achieving the best performance changes according to the Lc and vice versa. Additionally, a rapid drop in performance when the Ciono exceeds 25 wt% is due to the inhibited electron transfer in electrode and interface between the electrode and porous transport layers, and a critical ionomer concentration is proposed. Finally, high-performance PEMWE (6.882 A cm−2 at 2.05 V) is achieved with a low Lc of 0.5 mg cm−2 and a Ciono of 10 wt%.