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Amazon plans to make its own hydrogen to power vehicles
(www.theverge.com)
This is a most excellent place for technology news and articles.
The drones generally don't use compressed hydrogen (at least the ones I've seen). It's too dangerous. Instead they use a pellet based storage system. You can liberate hydrogen from it, but it's rate limited. It will burn, but it can't launch like a flaming rocket.
The downside is the pellet systems aren't as simple as just refilling the tank.