Photocatalytic decomposition of humic acids in anoxic aqueous solutions producing hydrogen, oxygen and light hydrocarbons.

Photocatalytic water splitting for hydrogen and oxygen production requires sacrificial electron donors, for example, organic compounds. Titanium dioxide catalysts doped with platinum, cobalt, tungsten, copper and iron were experimentally tested for the production of hydrogen, oxygen and low molecular weight hydrocarbons from aqueous solutions of humic substances (HS). Platinum-doped catalyst showed the best results in hydrogen generation, also producing methane, ethene and ethane, whereas the best oxygen production was exhibited by P25, followed by copper--and cobalt-containing photocatalysts. Iron-containing photocatalyst produced carbon monoxide as a major product. HS undergoing anoxic photocatalytic degradation produce hydrogen with minor hydrocarbons, and/or oxygen. It appears that better hydrogen yield is achieved when direct HS splitting takes place, as opposed to HS acting as electron donors for water splitting.