The 20 vehicles, which produce no pollution from their exhausts, will serve the number 7 route between East Acton and Oxford Circus.
The new buses, built in Northern Ireland, unveiled on Wednesday, can be charged once a day within five minutes and the only direct by-product is water.
They will run on hydrogen cells from a plant in Runcorn, using waste hydrogen from an industrial plant.
A greener process will be used from 2023, with cells being produced through electrolysis powered by an offshore windfarm.
Mayor of London Sadiq Khan said: “We have made real progress in London to clean up our air, but we still have a long way to go because toxic air pollution in our city is still leading to thousands of premature deaths every year and is stunting the growth of children’s lungs.
“Our investment in these hydrogen buses is not only helping us to clean up London’s air, but is supporting jobs and local economics across the UK.”
TfL hopes to to make all London buses zero emission by 2030.
