They suck. Maximum round trip efficiency is 37% in the best case scenario, and mostly worse. Hydrogen is a terrible store of energy, inefficient, ineffective and hard to work with.

Green hydrogen is essential for the roughly 90 million tons of it we will still use once we mostly eliminate the major demand sources of refineries and fertilizer, but there's no room or need for hydrogen as a fuel.

https://cleantechnica.com/2021/12/07/shrinking-hydrogen-demand-hydrogen-decarbonization-will-have-major-climate-benefits/