Polarization characteristics of a low catalyst loading PEM water electrolyzer operating at elevated temperature

The effect of temperature and pressure, and diffusion layer thickness is assessed on performance of a proton exchange membrane water electrolyzers (PEMWEs) with an ultralow iridium oxide (IrO2) loading (0.1 mg cm−2) anode prepared by electrodeposition and a Pt/C catalyzed cathode with a Pt loading of 0.4 mg cm−2. Increasing pressure to 2.5 bar at 120 °C enhances the water electrolysis current, so the anode electrodeposited with 0.1 mg cm−2 IrO2 gives a current density of 1.79 A cm−2 at 1.6 V, which is comparable to the conventional powder-type IrO2 electrode with 2.0 mg cm−2 at a temperature of 120 °C and pressure of 2.5 bar. The major factors for cell performances are rationalized in terms of overpotentials, water flow rates and thickness of diffusion layers, based on polarization behavior and ac-impedance response. [Display omitted] •IrO2 anodes with ultralow loading (0.1 mg cm−2) were fabricated by electrodeposition.•The effect of operating conditions on PEMWE performance was studied at 120 °C.•The current density at 1.6 V was as high as 1.79 A cm−2 at 120 °C and 2.5 bar.•Water transport characteristics in a PEMWE were experimentally examined.