When there is no sunlight, previously stored excess hydrogen, could be used creating the prospect of a perpetual source of power that only requires water and intermittent sunlight.
One of the by-products of research into solar cells for electricity production has been the investigation of solar energy to produce other sources of energy or useful products such as hydrogen fuel.
In this case a panel made at Rice University integrates catalytic electrodes and perovskite solar cells that, when triggered by sunlight, produce electricity. The current flows to the catalysts that turn water into hydrogen and oxygen, with a sunlight-to-hydrogen efficiency as high as 6.7 percent.
The device has two series-connected perovskite solar cells (PSCs) and two cobalt-phosphide CoP catalyst electrodes. The use of PSCs and CoP-catalysed water splitting is not new but Rice has packaged the two together in a single module that can be dropped into sunlit water and produce hydrogen without any other input. This is aided by the use of polymer insulating film called Surlyn.
The authors state that the module, while suitable for further efficiency optimization, is a self-sustaining producer of fuel that should be simple to mass produce.
The work was performed in the Lab of Rice materials chemist Jun Lou at Brown School of Engineering. The lead author was Rice postdoctoral fellow Jia Liang and the work is reported in the American Chemical Society journal ACS Nano.
Next: Lower efficiency and lower cost
The most efficient PSCs have efficiencies of more than 25 percent but the materials for those PSCs are expensive and tend to be stressed by light, humidity and heat, the authors observed.
“Jia [Liang] has replaced the more expensive components, like platinum, in perovskite solar cells with alternatives like carbon,” Lou said. “That lowers the entry barrier for commercial adoption. Integrated devices like this are promising because they create a system that is sustainable. This does not require any external power to keep the module running.”
“With a clever system design, you can potentially make a self-sustaining loop,” Lou said. “Even when there’s no sunlight, you can use stored energy in the form of chemical fuel. You can put the hydrogen and oxygen products in separate tanks and incorporate another module like a fuel cell to turn those fuels back into electricity.”
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