An efficient composite membrane to improve the performance of PEM reversible fuel cells

Abstract

In this study innovative composite Nafion/GO membranes are tested at different GO loading (0.5% wt., 1% wt. and 1.5% wt.) in electrolyser and fuel cell mode (Unitized reversible fuel cell). Baseline Nafion membranes were used for comparison.Water uptake (WU), ion exchange capacity (IEC), tensile strength, TGA (thermogravimetric analysis) and SEM (scanning electron microscope) analysis are discussed. The SEM revealed the inclusion of GO into the Nafion matrix while the TGA showed an increased thermal stability of the membrane attributed to the inclusion of the carbon material. Moreover, the addition of GO improves the membrane tensile strength, obtaining a maximum enhancement of nearly 90%, while reducing the elongation ratio (80% for the Nafion and 45% for the 1.5% wt. GO membrane). Water uptake increased when increasing the content of GO due to its hydrophilic nature recording the highest values for the membrane with 1.5%wt. of GO (23% against 10% for the Nafion). An increase of IEC (almost 14%) is noticed when GO content is increased. The beneficial effect of GO on the IEC can be attributed to a non-uniform distribution of GO into the Nafion matrix but needs further investigation.Both fuel cell and electrolyser polarization curves were carried out using MEAs with an active area of 9 cm2 and a thickness of 50 μm. The temperature and the pressure were set to 20 °C and 1 atm respectively. Regarding fuel cell mode, the optimum loading of GO has been found to be 0.5%, registering the highest performance, 13% higher than Nafion. Regarding the electrolyser mode, the GO 0.5% wt. membrane, showed performance comparable to the Nafion. A comparison between Nafion based membranes at higher thicknesses showed that, adopting GO, it is possible to obtained similar performance with a reduced membrane thickness, keeping almost equal the performance and the average round trip efficiency (26.1% for the GO and 26.6% for the Nafion). In commercial applications such characteristics allows to strongly reduce the cost of materials.Durability and stability of the GO/Nafion membrane should be properly investigated in successive studies as such membranes are subjected to a rapid deterioration of their performance.