Catalyst layer structure properties on hydrogen fuel generation performance of proton exchange membrane water electrolyzers

The catalyst layer (CL) is one of the important components determines the hydrogen fuel generation performance of a proton exchange membrane water electrolyzer (PEMWE). This work developed an analytical mathematical model of a PEMWE by considering a real structure of CL and the conductivities of the membrane (MEM) and CL, the impact mechanism of CL structure properties on the electrolysis voltage, activation overvoltage and ohmic overvoltage as well as power consumption under different operating conditions is investigated. The CL thickness, porosity and ionomer content show a great impact on the water electrolysis performance. A decrease in CL thickness could cause a high activation overvoltage but lower ohmic overvoltage. Increasing the CL porosity by lowering the ionomer content leads to a decrease in the activation overvoltage but yields a high ohmic overvoltage. Therefore, a PEMWE should be designed with a reasonable CL thickness and porosity. The PEMWE is found to show the lowest power consumption for a CL thickness of 8 μm and a porosity of 0.3. In addition, the impact of the inlet water velocity and temperature on the electrolysis performance is also investigated. It is shown that considering the rate of hydrogen production and the power consumption, inlet water flow rate of the electrolysis should be within the 0.2–0.5 m s−1 range. Moreover when the current density is 1 A cm−2, every 10 ℃ increase in temperature will reduce the electrolysis power density by 0.04 W cm−2, however, we should consider the ability of the component of the PWMWE to withstand high temperatures.