Experimentally determined reduction of both ohmic and mass transport overpotential due to femtosecond laser-induced surface structuring of titanium-based porous transport layers at the interface to the catalyst layer.

Information on proton exchange membrane water electrolysis performance is often obtained from full cell measurements. The level of detail of this information is, however, comparably low. This contribution analyzes kinetic parameters for anode and cathode reactions separately as a step towards an extended loss breakdown through a salt bridge reference electrode. The reference electrode setup is shown in detail, and qualitative measurements are discussed. Oxygen evolution reaction and hydrogen evolution reaction Tafel slopes and exchange current densities for both reactions are reported. An outlook on future use cases for the salt bridge reference electrode is given and supported by measurement data.

In this work, we use a method to separate the total oxygen mass transport coefficient into molecular, Knudsen, and ionomer contributions. Therefore, limiting current density measurements are carried out as a function of the diluent gas (He, N2, CO2), temperature (30, 50, 80°C), relative humidity (50, 75, 100%), and oxygen concentration (1, 3, 5, 7%) using state of the art membrane electrode assemblies with three platinum loadings (0.05, 0.1, 0.15 mg/cm2). As expected, the molecular diffusion coefficient is independent of the platinum loading, but increases with temperature to a varying degree depending on the humidity level. On the other hand, the Knudsen diffusion coefficient increases with increasing electrochemical active surface area and temperature, and with decreasing relative humidity. The separation procedure includes a novel feature to isolate the ionomer mass transport resistance. Its interpretation as well as the method’s reliability are critically questioned using operating condition dependencies.