Self-assembly of durable Nafion/TiO2 nanowire electrolyte membranes for elevated-temperature PEM fuel cells

Abstract TiO 2 nanowire-reinforced Nafion composite membranes for elevated temperature fuel cells are developed by self-assembly of positively charged TiO 2 nanowires and negatively charged Nafion molecules at low pH value condition. The TiO 2 nanowires are synthesized using a hydrothermal process. The Nafion-TiO 2 nanowire composite membrane, in which TiO 2 nanowires were dispersed uniformly, is prepared by solution-casting assisted with self-assembly. At 50 RH% and 90 °C, the cell assembled with Nafion/TiO 2 nanowires composite membranes (5 wt% TiO 2 ) has a relatively stable performance, and achieves a voltage of 0.59 V at a current density of 600 mA cm −2 , about 93% of that at 100 RH%. Self-assembly of the TiO 2 nanowire also improves the mechanical properties of the composite membrane both at different temperatures and humidity conditions. At the temperature close to the glass transition temperature, the TiO 2 nanowires remarkably reinforce the physical dimension of the membrane when the Nafion polymer structure is destroyed. In an in situ RH-cyclic accelerating experiment, the degradation of the open circuit voltage of the fuel cell assembled with Nafion-TiO 2 nanowire composite membrane (5 wt%) reaches 6.1 mV/h, compared to 16.3 mV/h for a fuel cell assembled with a recasting of pure Nafion membrane.

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