[tarice]

In space, the atmosphere can't filter out any of the sunlight, nor can clouds/water absorb some of its energy, which results in about 30% more energy[1].

Plus, if you're not near any objects that can block the sun (i.e. Earth/Moon), you get full, intense sunlight 24-hours a day.

And you can use some of that sunlight to just directly heat the water, which makes it easier to split.

Given all that, I'd say that it's very likely you could get enough energy to split water in space.

[1] http://en.wikipedia.org/wiki/Sunlight

[daeken]

Not to mention that if you're in a near-zero gravity environment, you really don't have to do anything to keep the solar panels in place; structures just to keep things upright on Earth are expensive and bulky. Space architecture is so cool.