Poly(aryl piperidinium- co -tetramethylpiperidinyl oxide) Copolymers with Intrinsic Antioxidant Capability for Anion Exchange Membrane Water Electrolysis

Abstract Anion exchange membranes (AEMs) for water electrolysis may suffer from oxidative degradation under high-potential operating conditions due to the attack of reactive oxygen species (ROS). Addressing the oxidative durability challenge for high-performancewater electrolysis remains imperative. Here, we report the preparation of AEMs with intrinsic antioxidant capability by directly copolymerization of nitroxide radicals into poly(aryl piperidinium) copolymer backbones. A series of TEMPO-containing AEMs (TEMPO-PAP-x%) are synthesized by incorporation of 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (4-oxo-TEMPO). The resulting TEMPO-PAPs based membranes exhibit high hydroxide conductivity and tensile strength. Remarkably, after 480 h of immersion in Fenton’s reagent (3 ppm FeSO4, 1% H2O2), the TEMPO-PAP membrane could retain 99.25% of its mass, whereas pristine PAP retains only 81.77%. Electron paramagnetic resonance (EPR) spectroscopy confirms that the nitroxide radicals are consumed during radical attack, acting as efficient radical scavengers. In water electrolysis tests, the TEMPO-PAP-10% membrane delivers an outstanding current density of 5.65 A cm–2 at 2.0 V (80 °C, 1 M KOH), representing a 175% enhancement over PAP. This work establishes a new strategy for endowing AEMs with intrinsic antioxidant stability.