Effect of cathode ink formulation on the hydrogen crossover and cell performance of proton exchange membrane water electrolyzers

The permeation of H₂ through the membranes of proton exchange membrane water electrolyzers (PEMWEs) is a critical safety concern because of the risk of explosion when H₂ mixes with O₂ at the anode and increases in concentration. In this study, we investigated the modification of the cathode catalyst layer in the membrane electrode assembly as a strategy for achieving the safe operation of PEMWEs. The effects of the polytetrafluoroethylene (PTFE) content and type of ionomer in the cathode catalyst layer on the dissolved H₂ concentration, H₂ crossover, and electrochemical performance were investigated. The lowest dissolved H₂ concentration and H₂ permeation rate were achieved when 8 wt% PTFE was used. Consequently, the H₂ volume fraction in O₂ at the anode was less than 0.88 %. Additionally, using the Nafion ionomer (D520, ion exchange capacity: 1 mmol g⁻¹), H₂ volume fractions of 1.27 % and 1.34 % were obtained at 0.08 and 5 A cm⁻², respectively. These values are below the lower explosion limit of H₂ in O₂ (4 %), implying that the PEMWE can be safely operated in the low-to-high current density range under ambient pressure. These results provide key guidelines for the design of high-safety cathode catalyst layers for PEMWEs.