Polysulfone MEA with a seamless binder–membrane interface: Improved performance and gas-crossover control

The catalyst-coated membrane (CCM) approach offers a promising way to overcome the limitations of conventional alkaline water electrolysis (AWE), including high interfacial resistance, uneven catalyst distribution, and significant gas crossover. However, Nafion and other polymer binders for CCM often face a trade-off between catalyst-membrane adhesion and electrochemical performance due to their low chemical stability in concentrated alkaline solutions and poor structural integrity at the interface. Here, we report a CCM configuration using polysulfone (PSU) as the binder and N-methyl-2-pyrrolidone (NMP) as the solvent, achieving a current density of 1.8 A cm⁻² at 2.0 V and stable operation for 300 h. The shared PSU chemistry between the binder and the Zirfon® separator enables seamless interfacial contact, as NMP partially dissolves the PSU-rich separator surface, promoting polymer interdiffusion and chain entanglement. This integration reduces the ohmic resistance to 0.12 Ω cm² (from 0.15 Ω cm² for the Zirfon® UTP 500) and significantly enhances mechanical adhesion (0.5 kN m⁻¹ vs. 0.1 kN m⁻¹ for Nafion-based CCMs). The resulting cell achieves 1.80 A cm⁻² at 2.0 V with a low hydrogen crossover flux of 8.38 × 10⁻¹⁰ mol·cm⁻²·s⁻¹, outperforming a conventional Raney Ni (2.0 A cm⁻² at 2.11 V and 1.75 × 10⁻⁹ mol·cm⁻²·s⁻¹). This PSU-based CCM architecture offers a scalable, low-cost, and high-efficiency alternative for next-generation AWE systems.