Ann: MOU with Total Eren to Develop Green Hydrogen Project, page-107

Hydrogen is not used to drive a piston engine, rather it is used to power an electric motor via fuel cells.

Fuel cells make power by using fuel from a tank (though the fuel is pressurized hydrogen gas rather than gasoline or diesel). But, unlike an engine, a fuel cell doesn't burn the hydrogen. Instead, it's fused chemically with oxygen from the air to make water. In the process, which resembles what happens in a battery, electricity is released and this is used to power an electric motor (or motors) that can drive a vehicle. The only waste product is the water—and that's so pure you can drink it!