Highly fluorescent carbon quantum dots-Nafion as proton selective hybrid membrane for direct methanol fuel cells

Abstract

Herein, we explored the carbon quantum dots as potential inorganic filler to realize a Nafion hybrid membrane with much reduction in methanol crossover for direct methanol fuel cell and is first ever reported in the literature. Highly fluorescent carbon quantum dots is synthesized by simple hydrothermal process using Gelatin as source material and the formation of carbon quantum dots is confirmed by UV–Visible and Photoluminescence spectroscopy studies. The added carbon quantum dots filler promotes the ionic conductivity primarily via hydrogen bonding formation between plenty of hydrophilic groups exist in carbon quantum dots and sulfonic acid moieties in the Nafion matrix. Remarkably, the optimized Nafion-carbon quantum dots hybrid membrane shows about 33% reduction in methanol crossover and about 30% higher proton conductivity in relation to the pristine Nafion membrane. While utilizing in direct methanol fuel cell, a peak power density of 113 mW cm−2 is realized with optimized Nafion-carbon quantum dots hybrid membrane at 70 °C and ambient pressure which is about 75% higher in performance than that of pristine Nafion membrane operated under identical conditions.