Using only the sun to split water and make hydrogen

As cool as the promise of quick refueling and emitting only water is, fuel cells still have that sticky issue of needing hydrogen before they can really catch on. In spite of hydrogen being the most common element in the universe it almost never appears in isolation. Separating hydrogen from the compounds that it is usually a part of tends to take a lot of energy. The most common methods today are steam reformation of natural gas and electrolysis of water. The former unfortunately produces carbon dioxide as a byproduct and electrolysis uses electricity. Green hydrogen proponents can point to a lot research being done on various renewable means of hydrogen production - such as using tidal or geothermal energy to power electrolysis or by biological means - but we're not there yet.
Profs. Thomas E. Mallouk and W. Justin Youngblood at Penn State University have been working on a solar cell that can directly crack water into hydrogen and oxygen. Electrodes from the cells inserted into water can split the molecules. Unfortunately at this point the system is only about 0.3 percent efficient. The researchers are investigating a number of different catalysts to help stimulate the reaction. They are also looking at different dyes for the cell itself to improve the sensitivity to a larger portion of the light spectrum. Another issue is making the reaction self-sustaining. Currently much of the oxygen and hydrogen quickly recombines after splitting, limiting the amount of hydrogen that can be recovered. It's an interesting concept but clearly still a long way from being viable.


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