Design of hybrid organic-inorganic TEOS-PVA:PVP ion solvating membranes for alkaline water electrolysis

Abstract Ion-solvating membranes (ISMs) have recently attracted growing interest in alkaline water electrolysis (AWE), as hydroxide transport occurs through KOH-solvated pathways rather than through fixed cationic sites. However, it remains challenging to develop membranes that combine high hydroxide conductivity with low swelling and strong oxidative stability. Hybrid semi-interpenetrating xTEOS-PVA:xPVP membranes were prepared through acid-catalyzed TEOS sol–gel chemistry, combined with PVA:PVP polymer entanglement, followed by solution casting and KOH activation. X-ray diffraction analysis further confirmed the structural modification of the membranes, showing reduced crystallinity and the formation of an amorphous hybrid network after TEOS incorporation. Fourier transforms infrared spectroscopy results indicated the presence of Si–O–Si and suggested possible Si–O–C interactions, and residual silanol groups, confirming the successful integration of the silica network within the polymer matrix. Scanning electron microscopy images revealed a composition-dependent morphological evolution, from dense polymer films to more structured hybrid morphologies at intermediate TEOS contents. These structural changes had a clear effect on hydration and transport behavior. In general, increasing the TEOS content reduced WU and swelling, and also lowered methanol crossover, indicating the formation of a denser and more selective hybrid membrane structure. Hydroxide conductivity showed a marked improvement after the introduction of a moderate TEOS fraction at high PVP content. The membrane showing the best overall performance, 1T-PVA:1.5PVP, reached hydroxide conductivities of about 60 mS cm −1 at 25 °C and 100 mS cm −1 at 80 °C in 1 M KOH. In addition, TEOS incorporation significantly improved oxidative stability, with the same intermediate composition showing about 90% mass retention. The practical performance of this membrane was further evaluated in a single-cell AWE system using a commercial NiMoO 4 anode for oxygen evolution reaction and nickel foam cathode for hydrogen evolution reaction, where the optimized membrane achieved a cell voltage of about 2.56 V at 500 mA cm −2 . These results demonstrate that the combination of inorganic sol–gel crosslinking and polymer semi-interpenetration is an effective strategy for producing ISMs with high hydroxide conductivity, controlled swelling, and enhanced oxidative durability, making them promising candidates for alkaline membrane water electrolysis.