Sodium borohydride (NaBH4) has several limitations or drawbacks as a hydrogen carrier:
Expensive to Produce: Sodium borohydride is currently expensive to produce, which prevents its wide applications1. The current production is based on a 70-year-old Brown-Schlesinger process, which is capital and energy-intensive, requires high temperatures and high pressures, and generates large amounts of CO2
Ref.1.
Recycling Byproduct: Sodium borohydride leaves a byproduct known as sodium metaborate after the hydrolysis process2. This byproduct is very expensive to recycle
Ref2.
Thermodynamic Stability: Sodium borohydride’s thermodynamic stability seriously hinders its application to obtain hydrogen Ref3
https://mdpi-res.com/d_attachment/ca...s-12-00356.pdf.
Infrastructure Requirements: The infrastructure for handling and distributing sodium borohydride is not as well established as for other fuels. This could add to the cost and complexity of using sodium borohydride as a hydrogen carrier.
Environmental Impact: The production of sodium borohydride and the recycling of its byproduct could have environmental impacts, particularly if the processes are not managed properly.
However, research is ongoing to address these challenges and make sodium borohydride a more viable hydrogen carrier. For example, a team of Australian researchers has developed a chemical catalyst process that can quickly and cheaply convert sodium metaborate into sodium borohydride Ref2. The Kotai Hydrogen Project at John Curtin University is working on a method to make sodium borohydride 20 times cheaper Ref2.
https://fuelcellsworks.com/news/aust...n-powder-form/
For the most up-to-date information, it would be best to check the latest news or scientific publications.