Self‐Humidifying Membranes Based on Amine Functionalized Tungsten Oxide and Nafion for Proton Exchange Membrane Fuel Cells Operating at Low Relative Humidity

ABSTRACT The commercialization of proton exchange membrane hydrogen‐air fuel cells (PEM‐HA‐FCs) necessitates the development of durable, high‐performance PEMs capable of efficient operation under low relative humidity (RH) conditions. In this work, amino‐functionalized tungsten oxide was employed as an inorganic filler to enhance the proton conductivity of Nafion membranes at reduced RH. The amino functionalization was achieved through a silanization process utilizing (3‐aminopropyl)triethoxysilane (3‐APTES) as the precursor. XRD, FTIR, and TGA analyses confirmed the successful functionalization. The structural, morphological, thermo‐mechanical properties, along with the physicochemical and electrochemical characteristics of both Nafion/amino‐WO 3 composite membranes and recast Nafion membranes were systematically investigated. The amino‐WO 3 composite membrane achieved an outstanding proton conductivity of 0.0196 S cm −1 , approximately 2.5‐fold higher than the unmodified Nafion membrane under conditions of 20% RH and 80°C. Beyond enhanced proton conductivity, membrane electrode assemblies (MEAs) fabricated with Nafion/amino‐WO 3 composite membranes demonstrated satisfactory current density at 0.6 V, achieving 0.4 A cm −2 and 0.305 W cm −2 power density when operated at merely 20% RH and 80°C. Furthermore, the membrane containing 0.5% filler exhibited approximately 6‐fold improved chemical durability and 62% reduced H2 crossover relative to the recast Nafion membrane.