Researchers develop a new ultra-high-density sulfonic acid polymer electrolyte membrane for fuel cells, which can be used for vehicles and combined heat and power systems. Credit: Atsushi Noro
Researchers at Nagoya University in Japan, under a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO), have created poly(styrenesulfonic acid)-based PEMs with a high density of sulfonic acid groups.
A crucial element in eco-friendly polymer electrolyte fuel cells is a polymer electrolyte membrane (PEM), which produces electrical energy through the interaction of hydrogen and oxygen gases. Practical applications of 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 (158-194 °F) 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.
However, using a conventional synthesis process, it is difficult to synthesize PEMs with a high density of sulfonic acid groups. For instance, to increase the density of sulfonic acid groups in a poly(styrenesulfonic acid)-based PEM, the sulfonation reaction must be carried out over long hours or under severe conditions. It usually uses highly oxidizing substances, such as fuming sulfuric acid and chlorosulfonic acid.
Unfortunately, this leads to undesirable side reactions, such as cleavage of the backbone chains of the polymer. Therefore, to avoid unwanted side reactions during polymer synthesis, commercially available PEMs are usually synthesized to have a low density of sulfonic acid groups. READ MORE...
A crucial element in eco-friendly polymer electrolyte fuel cells is a polymer electrolyte membrane (PEM), which produces electrical energy through the interaction of hydrogen and oxygen gases. Practical applications of 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 (158-194 °F) 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.
However, using a conventional synthesis process, it is difficult to synthesize PEMs with a high density of sulfonic acid groups. For instance, to increase the density of sulfonic acid groups in a poly(styrenesulfonic acid)-based PEM, the sulfonation reaction must be carried out over long hours or under severe conditions. It usually uses highly oxidizing substances, such as fuming sulfuric acid and chlorosulfonic acid.
Unfortunately, this leads to undesirable side reactions, such as cleavage of the backbone chains of the polymer. Therefore, to avoid unwanted side reactions during polymer synthesis, commercially available PEMs are usually synthesized to have a low density of sulfonic acid groups. READ MORE...
