The device combines two technologies: a standard silicon solar cell, which converts sunlight into electricity, and chemical catalysts applied to each side of the cell. Together, these would create an electrochemical device that uses an electric current to split atoms of hydrogen and oxygen from the water molecules surrounding them.
The goal is to produce an inexpensive, self-contained system that could be built from abundant materials. Nocera has long advocated such devices as a means of bringing electricity to billions of people, mostly in the developing world, who now have little or no access to it.
"What's significant is that this paper really describes all this technology that is known, and what to expect if we put it all together," Cox says. "It points out all the challenges, and then you can experimentally address each challenge separately."
Winkler adds that this is a "pretty robust analysis that looked at what's the best you could do with market-ready technology."
The original demonstration leaf, in 2011, had low efficiencies, converting less than 4.7 percent of sunlight into fuel, Buonassisi says. But the team's new analysis shows that efficiencies of 16 percent or more should now be possible using single-bandgap semiconductors, such as crystalline silicon.
"We were surprised, actually," Winkler says: Conventional wisdom held that the characteristics of silicon solar cells would severely limit their effectiveness in splitting water, but that turned out not to be the case. "You've just got to question the conventional wisdom sometimes," he says.
The key to obtaining high solar-to-fuel efficiencies is to combine the right solar cells and catalyst -- a matchmaking activity best guided by a roadmap. The approach presented by the team allows for each component of the artificial leaf to be tested individually, then combined.
Check out Science Daily: Creation and storage of solar energy as hydrogen. Yea baby!!