The illusive photocatalytic water splitting reaction using sun light on suspended nanoparticles. Is there a way forward?
For many decades hydrogen production by photocatalytic methods have been pursued over a variety of semiconductors with probably over a thousand formulations of powder catalysts in many structures and compositions. Yet, with the exception of a few reports, water splitting to molecular hydrogen and oxygen has stayed illusive. The only reproducible results are those involving other additives to water: electron donors or acceptors yielding either hydrogen or oxygen, but not both. The consequence of this is a system unrelated to water splitting but simply driven by the organic or inorganic redox potential. One may argue that thermodynamic limitations indicate that an inorganic semiconductor with a band gap within the spectrum of sun light, and is stable in water, cannot split water. Otherwise, it would not have existed on earth.