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<p>Chitosan (CS) is a naturally occurring biopolymer that is readily accessible and widely used in various industrial applications. However, its low proton conductivity, particularly at elevated temperatures, poses challenges for its application as a proton exchange membrane for fuel cells (PEMFCs). The proton-conducting properties are notably affected by the degree of crosslinking and the proton sources present in the conductors. Nevertheless, these factors are often insufficiently addressed, particularly in the context of covalent-organic frameworks. This study describes the condensation reaction of CS and oxidized polyvinyl alcohol (OPVA) to yield a novel Schiff base that improves CS proton conductivity. The formation of the Schiff base (OPVA/CS) was confirmed through Fourier transform infrared analysis, which revealed a band at 1560&#xa0;cm<sup>−1</sup>, as well as a <sup>13</sup>C nuclear magnetic resonance signal at 176.79 ppm, both indicating the presence of azomethine groups. Interestingly, OPVA/CS exhibited significantly higher proton conductivity of 202 mS/cm compared to CS (49 mS/cm) at 100&#xa0;°C, highlighting its potential for high-temperature PEMFC applications. Meanwhile, its methanol permeability was significantly lower than that of CS and Nafion, measuring 8.654 × 10⁻⁷ cm²/s compared to 5.358 × 10⁻⁷ cm²/s and 1.550 × 10⁻⁶ cm²/s, respectively. Additionally, both the particle size and surface charge density of OPVA/CS were reduced. This study presents a novel approach to producing eco-friendly membrane materials that can replace traditional non-biodegradable membranes. It highlights the potential of biopolymer-based membranes to advance sustainable fuel cell technologies.</p>

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Proton conductivity amelioration of chitosan via novel Schiff base formation with oxidized polyvinyl alcohol for proton exchange membrane

  • 期刊论文

  • 发表日期：

    2025年3月12日

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  • Qana A. Alsulami,
  • Wafa A. Bawazir,
  • Sherif M. A. S. Keshk

摘要

Chitosan (CS) is a naturally occurring biopolymer that is readily accessible and widely used in various industrial applications. However, its low proton conductivity, particularly at elevated temperatures, poses challenges for its application as a proton exchange membrane for fuel cells (PEMFCs). The proton-conducting properties are notably affected by the degree of crosslinking and the proton sources present in the conductors. Nevertheless, these factors are often insufficiently addressed, particularly in the context of covalent-organic frameworks. This study describes the condensation reaction of CS and oxidized polyvinyl alcohol (OPVA) to yield a novel Schiff base that improves CS proton conductivity. The formation of the Schiff base (OPVA/CS) was confirmed through Fourier transform infrared analysis, which revealed a band at 1560 cm−1, as well as a 13C nuclear magnetic resonance signal at 176.79 ppm, both indicating the presence of azomethine groups. Interestingly, OPVA/CS exhibited significantly higher proton conductivity of 202 mS/cm compared to CS (49 mS/cm) at 100 °C, highlighting its potential for high-temperature PEMFC applications. Meanwhile, its methanol permeability was significantly lower than that of CS and Nafion, measuring 8.654 × 10⁻⁷ cm²/s compared to 5.358 × 10⁻⁷ cm²/s and 1.550 × 10⁻⁶ cm²/s, respectively. Additionally, both the particle size and surface charge density of OPVA/CS were reduced. This study presents a novel approach to producing eco-friendly membrane materials that can replace traditional non-biodegradable membranes. It highlights the potential of biopolymer-based membranes to advance sustainable fuel cell technologies.