Sol–Gel Fabrication of Hybrid Semi-Interpenetrating Ion-Solvating Membranes by TEOS Crosslinking for Alkaline Electrolyzers

Abstract. Ion-solvating membranes are an emerging membrane class for alkaline water electrolysis, where hydroxide transport occurs through KOH-solvated pathways rather than fixed cationic groups but achieving high conductivity without excessive swelling and poor oxidative durability remains challenging. Here, we design hybrid semi-interpenetrating xTEOS–PVA:xPVP membranes by combining acid-catalyzed TEOS sol–gel crosslinking with PVA/PVP polymer entanglement, followed by solution casting and KOH activation. FTIR confirms the formation of Si–O–Si and Si–O–C linkages with residual silanols, demonstrating an inorganic network integrated within the polymer matrix. SEM reveals a composition-dependent morphology transitioning from dense polymer films to textured hybrid structures at intermediate TEOS loadings and re-densified surfaces at the highest TEOS contents. This structural evolution governs hydration and transport: water uptake and swelling decrease with TEOS, while hydroxide conductivity shows a step increase upon introducing a small TEOS fraction at high PVP content, reaching ~60 mS cm-1 at 25 °C and ~100 mS cm-1 at 80 °C in 1 M KOH for the optimal composition (1T-PVA:1.5PVP). Importantly, TEOS incorporation markedly enhances oxidative stability, with ~90% mass retention near the same intermediate composition. The results demonstrate that inorganic sol–gel crosslinking plus polymer semi-interpenetration can generate well-solvated transport pathways without excessive swelling, enabling membranes that combine high OH- conductivity with improved oxidative durability for alkaline membrane electrolyzers.