Designing a micro-cellulose membrane for hydrogen fuel cells

In this paper we describe the use of micro-cellulose, as obtained directly from cellulose filter paper, treated with weak acids, and reinforced with resorcinol bis(diphenyl phosphate) (RDP), for incorporation into the Membrane Electrolyte Assembly (MEA) of proton exchange membrane fuel cells (PEMFCs). The addition of RDP created a film on the cellulose fibers, preventing gas crossover and improving proton dynamics. FTIR analysis showed RDP binding to cellulose hydroxyl groups via the phenolic segments, while citric and phosphoric acids hydrolyzed the cellulose, causing RDP to bind via the P-O site. NMR analysis confirmed strong hydrogen bonding between RDP and cellulose, resulting in low proton mobility. However, RDP introduced after acid treatment, and binding at the P-O site, significantly enhanced proton mobility. Testing MEAs with RDP-treated cellulose filter membranes achieved a maximum power output of 4.9 mW cm⁻² at 80 °C with only 0.1 mg cm⁻² of platinum group metal loading. Treatment with citric or phosphoric acid increased power output by 141% and 120%, respectively, reaching a peak at 60 °C. The highest power output (16 mW cm⁻² in air, 34.3 mW cm⁻² in oxygen) was achieved with a mixed acid-treated membrane, displaying an ion exchange capacity of 0.1 m_eq. g⁻¹ and 226% power enhancement. The membrane remained stable at 60 mA for 100 hours, with an 8% voltage loss. This work shows that cellulose filter paper, which requires minimal additional processing and is easily recycled, can provide a cost-effective, environmentally sustainable choice for low power PEMFC applications.