Investigation of KOH‐doped PVA‐based membrane electrolytes cross‐linked with tartaric acid for DMAFCs

Abstract

This research focused on the development of anion exchange membrane electrolytes suitable for direct methanol alkaline fuel cells (DMAFC) by employing a straightforward blending and solution casting process complemented by subsequent heat treatment. Tartaric acid (TA) was employed as a cross‐linking agent to enhance the heat resistance and structural integrity of the PVA matrix. The distinctive attributes of the PT (PVA and tartaric acid blend) samples, including water absorption and swelling capacity, were comprehensively investigated with respect to variations in both TA content (expressed as wt. % relative to the PVA matrix) and alterations in the duration of thermal treatment. Cross‐link formation between the polymer chains and TA was determined using FTIR analysis. The samples were subjected to comprehensive analysis, encompassing the determination of crystallinity via X‐ray diffraction (XRD), assessment of thermal stability using thermogravimetric analysis (TGA), investigation of morphology through scanning electron microscopy (SEM), and measurement of ionic conductivity using AC Impedance spectroscopy. The methanol permeability was measured to determine the selectivity values of the membranes. Subsequently, within the DMAFC system, the performances of the PT30‐3, PT40‐2, and PT40‐3 membranes, which exhibited the highest selectivities, were assessed. The contribution of the crosslinking process to the resistance of the membranes to oxidative conditions, as represented by the Fenton solution, was evaluated to assess the chemical stability of the membranes. The maximum power densities for PT30‐3 and PT40‐3 membranes reached 15.29 and 12.53 mW/cm2 at 30°C, respectively. These figures exhibited a notable increase, reaching 32.73 mW/cm2 for PT30‐3 and 31.72 mW/cm2 for PT40‐3 when the temperature was elevated to 60°C. This study confirmed that the crosslinking strategy using TA assisted by thermal treatment is very simple and competitive compared with other techniques reported in the literature. PT membranes are promising candidates for commercialization and utilization in DMAFC owing to their environment‐friendly nature, cost‐effectiveness, and high efficiency.Highlights TA cross‐linking improved the thermal and dimensional stability of PVA. The PT membrane properties varied with TA content and thermal treatment time. Some electrolytes in this study outperformed those previously reported for DMAFC. PT membranes offer efficiency, cost‐effectiveness, and eco‐friendliness for DMAFCs.