“Using state-of-the-art theoretical computations, the University of Kentucky-University of Louisville team demonstrated that an alloy formed by a 2 percent substitution of antimony (Sb) in gallium nitride (GaN) has the right electrical properties to enable solar light energy to split water molecules into hydrogen and oxygen, a process known as photoelectrochemical (PEC) water splitting. When the alloy is immersed in water and exposed to sunlight, the chemical bond between the hydrogen and oxygen molecules in water is broken. The hydrogen can then be collected.”
Indeed, it sounds to be a very good, clean and environmental-friendly, fast way to gain power, without pollution caused by the typical coal or natural gas burning processes.
However, there are also other factors, that we should take in consideration. For instance, hydrogen is a gas, actually an explosive one. Just think about the Hindenburg tragedy. It is very important to know for sure where this gas will be contained and if it is secure for us humans to live next to it. On the other hand, the mentioned gallium, also used in bright-lights LEDs isn't a cheap material. And the efficiency plays also an important role.
The idea seems to be good, but I think there are more researches needed, until we start to use this technique.