Gas phase photocatalytic water splitting of moisture in ambient air: toward reagent-free hydrogen production

Abstract

We report our recent results investigating photocatalytic water-splitting using water vapour. In this case we use well-defined photocatalysts made up of Al-doped SrTiO3 (SrTiO3:Al) loaded with a RhCrOx and CoOy co-catalyst in a batch phase reactor containing either water vapour dosed into N2 gas or real air samples. The catalyst samples are deposited onto an inert substrate and irradiated under variable intensity UV LED. Both hydrogen and oxygen are produced in approximately 2:1 stoichiometric ratio over a duration of over 6 h. Importantly, the back reaction of H2O formation from H2 and O2 gas is suppressed, even in air which is a high O2 environment. The production rates are found to be highly sensitive to the water vapour concentration and temperature of the reactor, as has been found previously for other types of photocatalysts. The photocatalysts are shown to be robust enough in high oxygen environment to actively produce hydrogen using water sourced from ambient air (without any conditioning). These findings suggest photocatalysis may be used as a portable, self-contained hydrogen source for energy in remote locations.