Industrial electrolysis is roughly 70% efficient. Generating electricity from it with a fuel cell is about 40%-60% efficient. There are (realistic) newer approaches to improve on this (up to 85% for fuel cells). And yes, it’s infinitely better than nothing.

[0] https://en.wikipedia.org/wiki/Electrolysis_of_water [1] https://en.wikipedia.org/wiki/Fuel_cell