I don't want to refill anything. Water is a finite resource too, not to mention purified water sufficient to perform this trick and the silica needed to make it work in the first place.
I want something that will last 2000+ charges and still work without me having to top it up, like the £50 car battery I use as the most powerful example of this, or the Li-Ion in my laptop, or the £2 AA rechargeable. As soon as we get to the point of "just add" anything, that anything will become more expensive, especially if you have to do it every charge (sure, you can top up an - old - car battery with some purified water and even acid if you're determined, but it's literally an occasional thing compared to how often the battery is depleted and recharged - i.e. every trip - and with modern batteries you can literally have a car go for ten years of use and not require maintenance at all and still hold a full-enough charge in winter).
Hydrogen fuel cells hold no special place in my geek-heart. All you do is shift the product I have to buy from batteries (which I buy so rarely it hardly matters) to little fuel canisters to charge the batteries. And until those fuel canisters give me the equivalent of 2000 times the run time of a set of batteries, I'm still running at a loss there.
They may be "greener" (in some senses) but they are far from ideal and may even be worse than we already have (now we have to make fuel cells, and canisters that can hold a dangerous fuel safely, and the fuel itself - instead of just a battery). And from a consumer point of view, they have to have fuel be sold for literally PENCE before they become advantageous over conventional batteries (and how long before kids work out a way to make those fuel canisters explode by some trick, and they buy up the stock on Halloween?).
Fuel cells are a step backwards, until they can literally recycle (like a rechargeable battery) or do not exhaust their fuel over their lifetime.