Travail de fin d'études en chimie et bio-industries : Influence of Impurities on Anion Exchange Membrane Water Electrolysis.

Abstract

Anion exchange membrane water electrolysis (AEMWE) is one of the key and emerging low-temperature technologies for sustainable and green hydrogen production. However, the long-term durability of anion exchange membrane (AEM) poses a significant challenge and remains a bottleneck in the way of widespread commercial deployment of AEMWEs. Throughout the course of this study, PiperION degradation was systematically investigated under in-situ electrochemical operation, ex-situ oxidative environment and accelerated stressing conditions with a particular focus on the Fenton and Fenton-like induced degradation mechanism in alkaline media. Electrochemical experiments validated the formation of in-situ hydrogen peroxide in alkaline media, and their concentration was found to be strongly dependent on the availability of oxygen during electrochemical operations. At the same time, trace metal impurities originating from KOH pallets, enabling in-situ electro-Fenton reactions induced highly reactive species. These species lead to attacking the piperidinium cationic head group and terphenyl PiperION backbone, causing severe structure and chemical degradation. To further elucidate the degradation mechanism, ex-situ controlled oxidative tests with varying concentration (1–3 wt% H₂O₂ with 1–4 ppm iron impurities) were performed under Fenton and Fenton-like conditions. To isolate the oxidative effect, time dependent thermally accelerated (60–80 °C) and alkaline exposure aging (1 3 M KOH) were individually performed. Result indicates that presence of iron impurity significantly accelerates degradation mechanism by catalyzing H₂O₂ induces radical species. Comparatively, aging experiments show slower and controlled degradation behaviors. The structural degradation mechanism is comprehensively characterized by using advanced analytical, chemical and physical techniques, indicating a systematic loss of functional groups, degradation of quaternary ammonium, alteration in hydration behavior, and decline in structure stability and integrity. Quantitative analysis further confirmed the progressive loss of quaternary cationic sites and hydrophilic functionalities. Overall, this study highlights controlling oxygen purging, formation of peroxide and the key impurities that can enhance the AEM durability during AEMWEs.