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.