How have fuel cells been used in public transportation?

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Diagram of a proton exchange membrane (PEM) fuel cell showing labeled layers, including flow field plates, electrodes, and the proton exchange membrane, with arrows indicating hydrogen and oxygen inputs, electricity generation, and water and heat as outputs. — fuel cell Proton exchange membrane (PEM) fuel cell
The proton exchange membrane is one of the most advanced fuel cell designs. Hydrogen gas under pressure is forced through a catalyst, typically made of platinum, on the anode (negative) side of the fuel cell. At this catalyst, electrons are stripped from the hydrogen atoms and carried by an external electric circuit to the cathode (positive) side. The positively charged hydrogen ions (protons) then pass through the proton exchange membrane to the catalyst on the cathode side, where they react with oxygen and the electrons from the electric circuit to form water vapour (H₂O) and heat. The electric circuit is used to do work, such as power a motor.

Fuel cells have been utilized in public transportation through the deployment of fuel cell vehicles by various municipalities across Japan, Europe, and the United States. These vehicles are often leased by local governments for use in mass transit systems and by municipal service personnel.1

While the technology has demonstrated its viability for these applications, widespread commercial adoption has faced challenges. Efforts to make fuel cell transportation competitive have been hindered by concerns regarding the explosive nature of hydrogen, its relatively low energy density, and the high costs associated with the platinum catalysts required for the electrochemical reactions that generate electricity. Despite these hurdles, government programs—particularly in regions like California—continue to support the development and integration of hydrogen fuel cell technology in the transportation sector.1