Splitting water with electricity then recombining in the fuel cell back to electricity is extremely inefficient compared to just charging a battery with eletricity.
It may make sense in cases where batteries aren't practical like ocean going container ships.
There was a time a couple of decades ago when it might have made sense for cars when battery power wasn't good enough but that time has passed.
There are already early stage projects in France (and I assume other places as well) where Siemens Gamesa is using prototype turbines that does exactly this at an offshore wind farm