Electrochemical Properties of Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) harness hydrogen oxidation and oxygen reduction to generate electricity with high efficiency and near-zero emissions. At the heart of a PEMFC lies a thin ion-conducting polymer membrane sandwiched between porous electrodes, each coated with a platinum-based catalyst. On the anode side, hydrogen molecules dissociate into protons and electrons; protons traverse the membrane while electrons travel externally to power a load before returning to the cathode. At the cathode, oxygen molecules combine with protons and electrons to form water. The electrochemical properties governing this process include proton conductivity of the membrane, oxygen reduction reaction kinetics on the catalyst surface, ionic and electronic resistances in catalyst layers, and mass transport of reactants and water. Water management is critical: adequate hydration sustains proton conductivity, whereas excessive water induces flooding in catalyst layers, impeding gas transport. Nanostructure of the ionomer within the catalyst layer and interfacial interactions between ionomer and catalyst strongly influence overall performance and durability.

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Electrochemical Properties of Proton Exchange Membrane Fuel Cells publication trend

The graph below shows the total number of articles in electrochemical properties of proton exchange membrane fuel cells across all publications each year (not limited to Nature Index journals).

Technical terms

Proton conductivity: Ability of the membrane or ionomer to transport protons under an electric field.

Oxygen reduction reaction (ORR): Electrochemical process at the cathode where oxygen molecules are reduced to water.

Ionomer: Polymer containing ionic groups (e.g. sulfonic acid) providing proton pathways within catalysts.

Equivalent weight: Mass of ionomer per mole of ionic groups, influencing water uptake and conductivity.

Mass transport resistance: Opposition to reactant movement through porous media, affecting reactant supply.

Electrochemical interface: Region where catalyst, ionomer and reactants meet, critical for charge transfer reactions.

References

1. Engineering Catalyst Layers for Next‐Generation Polymer Electrolyte Fuel Cells: A Review of Design, Materials, and Methods. Advanced Energy Materials (2021).
2. Proton Conduction and Oxygen Diffusion in Ultra-Thin Nafion Films in PEM Fuel Cell: How Thin?. Journal of The Electrochemical Society (2019).
3. Transport and Electrochemical Interface Properties of Ionomers in Low-Pt Loading Catalyst Layers: Effect of Ionomer Equivalent Weight and Relative Humidity. Molecules (2020).
4. Molecular Dynamics Study of Reaction Conditions at Active Catalyst-Ionomer Interfaces in Polymer Electrolyte Fuel Cells. Journal of The Electrochemical Society (2022).