The study of PTFE/Nafion/Silicate membranes operating at low relative humidity and elevated temperature

Abstract

The performance and stability of PTFE/Nafion/Silicate composite membranes (PNS membrane) were studied at low and medium operating temperatures with different humidity, and compared with the Nafion112 membrane at the same conditions. The PNS membrane was prepared by impregnation of PTFE/Nafion composite membrane via sol–gel process with TEOS (tetraethoxysilane). When operated cell at low temperature of 60 °C with 100% R.H. humidified H₂/O₂ gases, the PNS membrane performs better than Nafion112, with 1.0, and 0.4 W/cm², respectively. When operated cell at 60 °C with 37% R.H. humidified gases, the discharge stability of PNS membrane is stable than that of Nafion112, this is due to that silicate could hold more water in the PNS membrane at low relative humidity. While the inlet of cell gases temperature keeps at 80 °C, the cell temperature varied 90, 100, and 110 °C, with 20 psig back pressure, their relative humidities were 67, 48 and 33%, respectively. The stability of discharge current remains constant except in the case of cell temperature being as high as 110 °C. It is believed that silicate could hold water except in the case of cell temperature at 110 °C, which is resulted as the membrane dehydration. On the other hand, the Nafion112 cannot operate at low humidity with cell temperature higher than 80 °C owing to membrane dehydration. The silica modified PTFE/Nafion membrane shows the improving cell performance at lower relative humidity due to adsorbed water inside the membrane and catalyst layer.