Abstract
Mass transport losses (ηmtx) play a significant role at high current densities in polymer electrolyte water electrolyzers (PEWEs). Previous work has shown that ηmtx depends on the porous transport layer (PTL) structure, although a clear correlation between the material morphology and ηmtx has not been established. In this work, we experimentally determine the overpotential ηH +CLa associated with the proton transport in the anodic catalyst layer by measuring the ionic resistance in the catalyst layer using electrochemical impedance spectroscopy (EIS) and the transmission-line model. We found that overpotentials, including ηH +CLa, depend on the PTL morphologic surface properties.
Highlights
It is necessary to identify voltage losses in polymer electrolyte water electrolyzers (PEWEs) on the cell level in order to optimize the design for higher efficiency
Operating conditions – H2/N2 regime.—For the determination of resistance in the anode catalyst layer (RCHL+a), a N2-stream of 500 Nml min−1 was injected into the working electrode (WE) water loop, while the reference/counter electrode (RE/CE) was supplied with humidified H2 at 400 Nml min−1
Proton transport resistance in the anode catalyst layer.—So far, there have not been any attempts to experimentally determine the RCHL+a contribution to ηmtx
Summary
It is necessary to identify voltage losses in PEWE on the cell level in order to optimize the design for higher efficiency. The PEWE cell was operated potentiostatically at 1.0, 1.2 and 1.4 V, and the impedance was measured from 10 kHz to 100 mHz. The measurements were performed in the potential region with higher capacitance to eliminate the effects of the inductive elements.[8] No contribution of the faradaic current was observed at these potentials in the H2/N2 regime (cf Supplementary Material, Figure S3).
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