Deep eutectic solvents based on N, N, N-trimethyl propylsulphonate ammonium hydrosulfate-urea as potential electrolytes for proton exchange membrane fuel cell

Abstract

Deep eutectic solvents (DESs) have been synthesized by using N, N, N-trimethyl propylsulphonate ammonium hydrosulfate as the hydrogen bond acceptor (HBA) and urea as hydrogen bond donor (HBD) in capricious molar ratios. Fourier transform infrared spectrum, the proton nuclear magnetic resonance and carbon-13 nuclear magnetic resonance are employed to confirmed the chemical structures of N, N, N-trimethyl propylsulphonate ammonium hydrosulfate. The synthesized DESs are characterized by thermogravimetric analysis and Fourier transform infrared spectrum. The synthesized DESs exhibit excellent thermal stability, making them suitable electrolytes for proton exchange membrane fuel cell. The viscosity and conductivity of DESs are significantly affected by the molar ratio between HBD and HBA. The four samples are used as electrolytes to evaluate the fuel cell performance. The results indicate that the power density of the four samples decreases in the following order: DES with a molar ratio of HBA/HBD of 1:1 > DES with a molar ratio of HBA/HBD of 2:1 >N, N, N-trimethyl propylsulphonate ammonium hydrosulfate > DES with a molar ratio of HBA/HBD of 1:2. The DES with a molar ratio of HBA/HBD of 1:1 exhibits a significantly higher peak power density of 92.5 mW · cm−2 compared to the peak power density (48.5 mW · cm−2) observed without the addition of urea at 50 °C, while DES with a molar ratio of HBA/HBD of 1:2 displays a much lower peak power density of only 8.7 mW · cm−2 at 30 °C. The proton diffusion coefficient D is a critical factor that significantly impacts fuel cell performance. DESs as proton conducting media is a promising approach to improve cell performance in the proton exchange membrane fuel cell.