While only small amounts of platinum in dye-sensitized solar cells are required, it is expensive at US$1,500 an ounce.
The University team invented a novel approach to synthesize a unique 3D version of grapheme with a honeycomb-like structure. To do so, they combined lithium oxide with carbon monoxide in a chemical reaction that forms lithium carbonate (Li2CO3) and the honeycomb graphene. The Li2CO3 helps shape the graphene sheets and isolates them from each other, preventing the formation of garden-variety graphite. The Li2CO33 particles can be easily removed from 3D honeycomb-structured graphene by an acid.
The scientists determined that the 3D 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 3D honeycomb graphene. Then they put the solar cell in the sunshine and measured its output.
The cell with the 3D graphene counter electrode converted 7.8 per cent of the sun’s energy into electricity, nearly as much as the conventional solar cell using platinum (8 per cent).
The research has been funded by the American Chemical Society Petroleum Research Fund and the National Science Foundation. The article describing the work, 3D Honeycomb-Like Structured Graphene and Its High Efficiency as a Counter-Electrode Catalyst for Dye-Sensitized Solar Cells, coauthored by Hu, Michigan Tech graduate student Hui Wang, Franklin Tao of the University of Notre Dame, Dario J. Stacchiola of Brookhaven National Laboratory and Kai Sun of the University of Michigan, was published in the journal Angewandte Chemie, International Edition.