In a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO), researchers at Nagoya University in Japan have developed poly (styrenesulfonic acid)-based PEMs with a high density of sulfonic acid groups.
One of the key components of environmentally friendly polymer electrolyte fuel cells is a polymer electrolyte membrane (PEM). It generates electrical energy through a reaction between hydrogen and oxygen gases. Examples of practical fuel cells include fuel cell vehicles (FCVs) and fuel cell combined heat and power (CHP) systems.
The best-known PEM is a membrane based on a perfluorosulfonic acid polymer, such as Nafion, which was developed by DuPont in the 1960s. It has a good proton conductivity of 0.1 S/cm at 70-90 °C under humidified conditions. Under these conditions, protons can be released from sulfonic acid groups. Proton conduction in such membranes typically depends on the proton transport mechanism between protons, sulfonic acid groups, and water molecules. Typically, the higher the density of the sulfonic acid groups in the membrane, the higher the density of protons that can be released from the sulfonic acid groups; therefore, the higher density of the sulfonic acid groups usually results in higher proton conductivities.