Poly(pentafluorstyrene) based ionomers for electrochemical hydrogen pumps I – How electrode properties affect the performance

Electrochemical hydrogen pumps (EHPs) are a promising technology for isolating H2 from gas mixtures. This work implements novel proton-conducting binders into gas diffusion electrodes (GDEs) and investigates full-cell EHPs with a phosphoric acid-doped polybenzimidazole membrane. The morphological GDE properties are investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and argon gas sorption, revealing an extremely high catalyst layer porosity with phosphonated poly(pentafluorstyrene) (PWN70) ionomer. Adding the nonionic surfactant Triton X-100 to the catalyst ink significantly improves the distribution of poly(pentafluorstyrene)-imidazole (PPFSt-Imi) binder, increasing electrode porosity and cell performance. Furthermore, the hydrophobicity of all catalyst layers is probed by dynamic vapor sorption. At 200 °C, the EHPs demonstrate 99.98 % H$_2$ purity and 100 % H$_2$ recovery from a reformate gas mix at 95 % power efficiency. A durability test at 1.6 A cm$^{−2}$ proves stable electrode operation, highlighting the suitability of the employed binders for EHPs.