A field emission scanning electron microscopy (FESEM) image of 3-D honeycomb-structured graphene. The novel material can replace platinum in dye-sensitized solar cells with virtually no loss of generating capacity. Image: Hui Wang
One of the most promising types of solar cells has a few drawbacks. A scientist at Michigan Technological Univ. may have overcome one of them.
Dye-sensitized solar cells are thin, flexible, easy to make and very good at turning sunshine into electricity. However, a key ingredient is one of the most expensive metals on the planet: platinum. While only small amounts are needed, at $1,500 an ounce, the cost of the silvery metal is still significant.
Yun Hang Hu, the Charles and Caroll McArthur Prof. of Materials Science and Engineering, has developed a new, inexpensive material that could replace the platinum in solar cells without degrading their efficiency: 3-D graphene.
Regular graphene is a famously 2-D form of carbon just a molecule or so thick. Hu and his team invented a novel approach to synthesize a unique 3-D version with a honeycomb-like structure. To do so, they combined lithium oxide with carbon monoxide in a chemical reaction that forms lithium carbonate and the honeycomb graphene. The lithium carbonate helps shape the graphene sheets and isolates them from each other, preventing the formation of garden-variety graphite. Furthermore, the lithium-carbonate particles can be easily removed from 3-D honeycomb-structured graphene by an acid.
The researchers determined that the 3-D honeycomb graphene had excellent conductivity and high catalytic activity, raising the possibility that it could be used for energy storage and conversion. So they replaced the platinum counter electrode in a dye-sensitized solar cell with one made of the 3-D honeycomb graphene. Then they put the solar cell in the sunshine and measured its output.
The cell with the 3-D graphene counter electrode converted 7.8% of the sun’s energy into electricity, nearly as much as the conventional solar cell using costly platinum (8%).
Synthesizing the 3-D honeycomb graphene is neither expensive nor difficult, said Hu, and making it into a counter electrode posed no special challenges.
Source: Michigan Technological Univ.
