This sounds like an encouraging development:

With one bottle of drinking water and four hours of sunlight, MIT chemist Dan Nocera claims that he can produce 30 KWh of electricity, which is enough to power an entire household in the developing world. With about three gallons of river water, he could satisfy the daily energy needs of a large American home. The key to these claims is a new, affordable catalyst that uses solar electricity to split water and generate hydrogen.

Sounds very interesting, but let's not get too excited just yet. While Nocera paints a wonderful picture of every home having its own power generator -- which can also produce fuel for the family car -- there is some information missing from the linked story.

Wait, we know that this catalyst turns water into a a solar-power generating machine...isn't that enough? What else do we need to know?

I didn't think of it myself, but several commenters point out that the linked article makes no mention of how much the catalyst costs to produce, how much it will cost to use (from a consumer standpoint), and what its environmental impact might be.

See? That's how they get you.

Oh, don't get me wrong. There could still be something here--something amazing and potentially world-transforming. I have always loved the idea of making hydrogen feasible both as a solar power storage medium and a means of powering vehicles. But let's not go re planning our whole lives around it until we see a price tag.

UPDATE: Randall Parker looks at another big potential solar breakthrough.