Managing gas and ion transport in a PTFE fiber-based architecture for alkaline fuel cells

Hydrogen fuel cells are needed for long-haul, heavy-duty transportation applications that are beyond the range of electric vehicle technology. Recently, advances in membrane science have enabled alkaline fuel cells, which in principle do not require precious metal catalysts, to compete with fuel cells that utilize acidic membranes. Here, we combine cryo-electron microscopy, electrochemistry, and numerical modeling to understand the performance of the cathode of alkaline fuel cells, where oxygen combines with water to make hydroxide anions. We examine the conventional electrode architecture, where catalyst nanoparticles are supported on carbon and surrounded by a thin film of ionomer, with a new architecture of catalyst particles on gas-permeable fluorocarbon fibers. These studies show that the conventional architecture would work more efficiently with ionomers that are more permeable to oxygen. The fiber architecture manages oxygen and ion transport well, but its performance is limited by the activity of the catalyst.