16 December 2013

Splitting hydrogen and oxygen from water using sunlight, nanoparticles

Image Credit: jaroslava V / Shutterstock

University of Houston researchers, writing in the journal Nature Nanotechnology, report they have found a catalyst that can quickly generate hydrogen from water using sunlight, potentially creating a clean and renewable energy source.

The study involved the use of cobalt oxide nano-particles to split water into hydrogen and oxygen. Jiming Bao, lead author of the paper and an assistant professor in the Department of Electrical and Computer Engineering, said the researchers discovered the new photocatalyst and demonstrated the potential of nanotechnology in engineering a material’s property.

Bao said that photocatalytic water-splitting experiments have been tried since the 1970s, but this was the first to use cobalt oxide, as well as the first to use neutral water under visible light at a high energy conversion efficiency without a co-catalysts or sacrificial chemicals.

The researcher said that the team prepared the nanoparticles by using femtosecond laser ablation and through mechanical ball milling. He said that both of these ways worked equally well, despite their differences.

Different sources of light were used during the study, ranging from a laser to white light simulating the solar spectrum. Bao said he would expect the reaction to work equally well when using natural sunlight.

According to the researchers, once the nanoparticles were added and light was applied, the water separated into hydrogen and oxygen almost immediately, producing twice as much hydrogen as oxygen, which is expected when considering the 2 to 1 hydrogen to oxygen ratio in H2O water molecules.

The experiment could potentially be a source of renewable energy, but the solar-to-hydrogen conversion rate is too low to be commercially viable. Bao says a more feasible efficiency rate would be around 10 percent, rather than 5, meaning that 10 percent of the incident solar energy will be converted to hydrogen chemical energy by the process.

The team said that other issues that still need to be resolved include reducing costs and extending the lifespan of cobalt oxide nanoparticles.

Bao, who also has appointments in materials engineering and the Department of Chemistry, said that the experiment degrades too quickly right now. He said that more research still needs to be done in order to fix the problems that have emerged so far. Future work could include answering the question of why cobalt oxide nanoparticles have such a short lifespan. The team could also solve questions involving chemical and electronic properties of the material.

Efficient solar water-splitting using a nanocrystalline CoO photocatalyst, Nature Nanotechnology, DOI: 10.1038/nnano.2013.272

University of Houston

Now read: Team sheds new light on solar water splitting process


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