High pressure polymer electrolyte water electrolysis: Test bench development and electrochemical analysis

A test bench for a polymer electrolyte water electrolysis (PEWE) cell for high pressure operation of up to 100 bar in differential and balanced pressure mode is described. Important aspects referring to the design, safety and operability of the test bench and the design of a small scale electrolysis cell are described. The electrolyzer cell comprises a special compression mechanism which allows accommodating porous transport layers of different thickness and setting of the compression pressure independent of the clamping pressure. In order to analyze the electrochemical results with respect to the overpotentials, a power source with integrated high frequency resistance (HFR) as well as electrochemical impedance spectroscopy (EIS) measurement capabilities is implemented. The versatility of the test environment is demonstrated by comparing the DC, HFR and EIS data as a function of operating pressure, temperature (up to 70 °C) and current density (up to 4 A/cm2). With respect to pressurized operation of PEWE cells, only the differential pressure mode (hydrogen pressurized) shows the expected isothermal compression behavior, for balanced pressure operation a different characteristic is observed.