New photocatalyst for hydrogen generation works by irradiation with visible light

Making energy useable is a central problem of our civilization. Couldn't we simply imitate green plants and
use photosynthesis to transform light into chemical energy? In principle, we could: hydrogen can be catalytically released from water to drive fuel cells that produce electricity -- a clean source of energy that doesn't require fossil fuels. In theory, photocatalytic cells are easy to make. Simply put the catalyst in water, irradiate with sunlight, collect the hydrogen, and there you are. So what are we waiting for? It turns out not to be so simple after all.