(688f) Valorization of Lignin to Enhance Performance and Sustainability of High-Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFCs)

Phosphoric acid-doped polybenzimidazole (PBI) membranes hold promise for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) due to their good proton conductivity and resilience in anhydrous conditions. However, the efficacy of PBI-doped membranes is limited by phosphoric acid (PA) leaching from membrane at elevated temperatures, resulting from weak interaction energy between PA and PBI. The PA-leaching leads to diminished proton conductivity and mechanical integrity of the membranes. To tackle this issue, we have strategically cationized lignin and incorporated it within PBI membrane matrix. By adjusting cationization levels and PBI-to-cationic lignin ratios, we maximized ion-pair interaction, PA retention, and proton conductivity while preserving mechanical strength. Conductivity tests showed that these composite membranes outperform pure PBI ones, maintaining high proton conductivity at 160 °C for extended periods. This underscores the efficacy of cationic lignin in improving ion transport performance in HT-PEMFCs. Additionally, the cationized lignin, being sourced from natural, eco-friendly materials, enhanced the sustainability of the energy conversion technologies