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

Abstract

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.

Keywords:

• humic substances
• photocatalysis
• hydrogen generation
• doped titanium dioxide
• template synthesis

Acknowledgements

The authors thank Dr. Paul Boni and Mr. Frederic Luiszer (University of Colorado, Boulder) for the training and assistance in XRD and ICP-OES measurements, respectively.

Funding

The financial aid of Estonian Science Agency [Project IUT1-7], Estonian Science Foundation [grant GUS10] and US Civilian Research and Development Foundation [grant ESC2-2974-TL-09] is also greatly appreciated.