Phosphotungstic acid (HPW) molecules anchored in the bulk of Nafion as methanol-blocking membrane for direct methanol fuel cells

In the present study, a novel composite methanol-blocking polymer electrolyte membrane was prepared by anchoring water-soluble phosphotungstic acid (HPW) in bulk phase of Nafion through interactions between HPW and Cs⁺ ions. Results of morphology and elemental mapping analysis indicated that this composite membrane had a dense structure with uniformly distributed Cs-HPW clusters. The composite membrane exhibited a rather low methanol diffusion coefficient (P, 0.97×10^-6cm²s^-1) and also the comparable conductivity (σ, 3.6×10^-2Scm^-1) contrast with pristine Nafion (σ, 5.1×10^-2Scm^-1). The selective factor (σ/P) of the composite membrane was six times higher than that of pristine Nafion. Single cell performance results showed that the maximum power density increased by 26% over the cell performance of pristine Nafion under the same conditions.