Sulfonated polysulfone composite membranes with tailored interfacial hydrogen bond network for efficient proton exchange membrane water electrolysis

Both chemical compositions of ionomers and surface properties of nanofillers significantly impact the performances of composite proton exchange membranes (PEMs) for water electrolysis. Despite progress in optimizing the chemical compositions of ionomers, it remains challenging to rationally modulate the micro/nano interface between nanofillers and ionomers due to the undesirable surface functionalization of nanofillers. In this study, core-shell silica@poly(1-vinylimidazole) (SiO₂@PVI) nanoparticles with tunable grafting densities are fabricated via sonochemical technique and incorporated into sulfonated polysulfone (SPSF60) ionomer. The SiO₂@PVI nanoparticles strengthen the interfacial hydrogen bond with SPSF60 by elevating the surface tethered imidazole groups, yielding a customizable interfacial network that further boosts the proton conductivity and stability of SPSF60/SiO₂@PVI membranes. As a result, integrating the SPSF60/SiO₂@PVI-12C membrane into a water electrolyzer achieves an exceptional operating current density of 5.84 A/cm² at 2.0 V and 80 °C, which is 31.2 % higher than that with pure SPSF60. Moreover, the electrolyzer's durability is doubled due to the enhanced stability of the modified membrane. This study underscores the critical role of ionomer/filler interfacial structure on properties of composite PEMs, presenting an effective strategy to enhance the performance of proton exchange membranes for water electrolysis through interface modulation.