05. 20. 2025
How Does a Hydrogen Engine Work?

Hydrogen engines operate by using gaseous hydrogen stored in tanks with oxygen from ambient air as fuel, producing only water vapor as exhaust emissions. By comparison, petroleum engines emit air pollution.
Fuel cells work by forcing hydrogen through an anode and oxygen through a cathode, where electrons and protons combine with electrons in hydrogen molecules to produce electricity and water as output. Fuel cells can be easily assembled in stacks and produced cost effectively.
1. Hydrogen Storage
Hydrogen is stored in a thick-walled and crash-tested tank under the rear seat, where it’s then piped through a fuel cell where hydrogen and oxygen combine to generate electricity and water; that electricity then powers an electric motor that powers the vehicle (similar to battery electric vehicles).
Motor energy also charges a buffer battery, acting as temporary storage for the fuel cell’s output so the vehicle can travel for longer than BEVs can. Like other electric cars, FCEVs use regenerative braking to recover energy and put it back into their batteries.
2. Fuel Cell
There are various types of fuel cell technologies, all operating differently. But in general, hydrogen atoms enter at the anode and undergo chemical reactions which strip them of electrons before being forced by electrolyte (which separates two electrodes) into an external circuit for electricity production. When they return to cathode they combine with oxygen to reform hydrogen which releases heat and pure water as a by-product.
Hydrogen fuel cells differ significantly from traditional internal combustion engines by not producing criteria pollutants like nitrogen oxides. They are up to twice more efficient than gasoline engines and offer an equivalent driving distance of approximately 500 kilometers.
Just minutes are all it takes for vehicles to refuel at either a standard electric terminal or hydrogen station, expanding their range and replenishing their fuel tank. Thanks to a synergistic relationship between hydrogen system and lithium-ion battery technology, energy autonomy is high; Renault Master Van H2-TECH’s combination of 33 kWh battery capacity with 30 kWh hydrogen capacity gives an approximate driving range of 400 kilometers.
3. Electrochemical Reaction
Electrochemical reaction is a type of energy conversion using metallic electronic conductors as conductors to generate current. Electrons with opposite charges move across a circuit known as its cell potential to drive the chemical reaction and spur its progress.
An anode oxidises the fuel and releases electrons which are drawn into an external circuit by an ion-charged electrolyte, creating an uninterrupted electric current to power an engine. Once these electrons reach their destination at the cathode they combine with oxygen to cause reduction, with any excess ions then being taken up by water molecules leaving only pure water vapour as byproduct.
Fuel produced from renewable resources offers a more environmentally-friendly option to fossil fuels. Biodiesel’s wider flammability range and lower auto-ignition temperature than gasoline engines makes it more suitable for long haul applications where refuelling may be limited or unavoidable, such as longer haul truck applications.
4. Electricity Generation
Hydrogen engines combine gaseous hydrogen with air as fuel for combustion engine operation, where it is ignited with a spark plug to generate mechanical energy and is then released as exhaust emissions in the form of nitrogen oxides and, if fuel was not pure enough, carbon dioxide.
Hydrogen-powered cars differ from battery electric vehicles (BEVs) in that they generate their own electricity using fuel cells. The electricity produced can either power directly into their electric motor and extend driving range or be stored as buffer battery power for later use.
A fuel cell system comprises several components, such as the hydrogen tank with its associated receptacle for refilling at regular gasoline stations, membrane electrodes on its fuel cell stack and power electronics controller. These two devices coordinate electricity flow between fuel cell stack, traction battery and electric motor as well as temperature management and ensure all components of the system function optimally.
5. Exhaust
Hydrogen entering an anode separates into ions and electrons that travel through a conductive collector to generate electricity, creating current that powers the vehicle. At cathode level, when combined with oxygen they form water vapor which generates additional electricity; when released through the exhaust system as pure water vapor without harmful emissions.
Fuel tanks must be designed and constructed carefully in order to withstand this immense internal pressure, while hydrogen needs to be consumed quickly so refueling times are comparable with gasoline cars. Since HICE vehicles emit water vapor instead of greenhouse gasses, HICE vehicles are environmentally-friendly. Unfortunately, HICE engines are less energy-efficient due to losses at each step in conversion (chemical to heat to mechanical energy conversion).
Conclusion
Hydrogen engines—whether through hydrogen internal combustion engines (HICE) or fuel cell electric vehicles (FCEVs)—offer a promising path toward cleaner transportation by producing only water vapor as a byproduct. As renewable hydrogen production and refueling networks expand, hydrogen-powered vehicles may well become a practical and eco-friendly alternative to traditional fossil fuel engines.
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