Fuel cells are electrochemical devices that produce usable electricity by the catalyzed combination of a fuel such as hydrogen and an oxidant such as oxygen. In contrast to conventional power plants, such as internal combustion generators, fuel cells do not utilize combustion. As such, fuel cells produce little hazardous effluent. Fuel cells convert hydrogen fuel and oxygen directly into electricity, and can be operated at higher efficiencies compared to internal combustion generators.
A fuel cell such as a proton exchange membrane (PEM) fuel cell typically contains a membrane electrode assembly (MEA), formed by a catalyst coated membrane disposed between a pair of gas diffusion layers. The catalyst coated membrane itself typically includes an electrolyte membrane disposed between a pair of catalyst layers. The respective sides of the electrolyte membrane are referred to as an anode portion and a cathode portion. In a typical PEM fuel cell, hydrogen fuel is introduced into the anode portion, where the hydrogen reacts and separates into protons and electrons. The electrolyte membrane transports the protons to the cathode portion, while allowing a current of electrons to flow through an external circuit to the cathode portion to provide power. Oxygen is introduced into the cathode portion and reacts with the protons and electrons to form water and heat. The MEA also desirably retains water to preserve proton conductivity between the layers, particularly at the electrolyte membrane. A reduction in proton conductivity between the layers correspondingly reduces the electrical output of the fuel cell.
A common problem with fuel cells involves carbon monoxide poisoning of the catalyst layers, which reduces the effectiveness of the catalyst layers. To counter the reduction, higher catalyst concentrations are required to provide effective levels of electrical output. This correspondingly increases the material costs for manufacturing fuel cells. One technique for reducing the carbon monoxide poisoning includes operating the fuel cell at higher temperatures (e.g., above 100° C.). However, the elevated temperatures cause the water retained in the MEA to evaporate, thereby reducing the proton conductivity within and between the layers. As such, there is a need for an electrochemical device that preserves proton conductivity while operating at high temperatures.
USPTO Backgrounds
USPTO Backgrounds