Hydrogen is a bad idea. It requires a lot of energy to produce and involves the breakdown of water. The most precious commodity on the planet. Once the water is gone we are screwed.
We don't really know where water came from or how fast it is escaping into space, there hasn't really been a lot of study on the matter ( thank god or the politicians would have another yoke around our necks with that )
What, pray tell, do you suppose is produced by the combustion of hydrogen as a fuel?