The zero emission train project will demonstrate how the country’s railways could be decarbonised by phasing out diesel within 15 years.
The University of St Andrews is seeking a design partner for the next stage of the Scottish Enterprise and Transport Scotland scheme.
It will involve the conversion of one of a fleet of electric ScotRail trains which were phased out last year.
The contract, also involving the University of Strathclyde, will include system design, installation and demonstration of the train on a line away from the rail network.
It follows the concept design for conversion of the Class 314 train by Brodie Engineering in Kilmarnock and London-based Arcola Energy.
A Scottish Enterprise spokesperson said: “It is planned to make demonstration of the train a centrepiece of the global COP26 conference being hosted in Glasgow next year.”
However, cheaper hydrogen production may be required to make it a viable fuel since the gas remains far more expensive than diesel.
Scottish Enterprise managing director of economic development Linda Hanna said: “This is a hugely exciting project for the rail industry in Scotland and for our small and medium-sized enterprises.
“A key objective of the project is to provide the rail supply chain with the opportunity to develop their skills and advance their knowledge of the application of hydrogen fuel cell technology on passenger rolling stock, including hydrogen supply and refuelling infrastructure.
“So it’s an opportunity to demonstrate innovation and get involved with an industry of the future.
"In turn, this creates quality jobs and supports our national ambitions for a net zero carbon economy.”
Professor John Irvine, who specialises in energy materials at the University of St Andrews, said: “This is another key step forward for Scotland as we advance towards a hydrogen-enabled low-carbon economy.
“Hydrogen will be very important in our low-carbon future, especially in delivering clean transport options.
“This is also key for supporting the development of the Scottish supply chain and with the Scottish companies who are breaking into these new markets.”