New Thin Film Solid Oxide Fuel Cells (TF-SOFC) Capable of Storing Energy

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Alternative Fuels: Recent Developments

A new study has made a major advance in this field – performed by the Harvard School of Engineering and Applied Science, the results were published in Nano Letters. Dr. Quentin Van Overmeere was the leading scientist of this research; he worked together with Mr. Kian Kerman and Prof. Shriram Ramanathan, principal investigator of the research group.

(a) Structure of the TF-SOFC; (b) Evolution of the potential with time. Image reproduced with permission from Van Overmeere, et al.

Key to Solid Oxide Fuel Cell Charge: Multilayer Anode

Dr. Van Overmeere and his co-workers compared the performances of three TF-SOFC made with different anodes.

  • In the first case, the anode was made of platinum (Pt), a high-performance electrode material.
  • In the second case, vanadium oxide was used; because vanadium oxide can exist in different oxidation states– VO2, V2O5, V6O13, V3O7 – it is indicated by the general formula VOx.
  • In the third case, a bilayered anode, made of Pt + VOx, was considered.

In all three cases, the electrolyte was made of yttria stabilized zirconia (YSZ), a mixture of the oxides of yttrium and zirconium, Y2O3 and ZrO2 respectively. The image to the right shows the structure of the TF-SOFC.

SOFC Test Results: VOx Provides Lasting Electric Charge

For all three thin-film solid-oxide fuel cells, the voltage and the electric current were measured as a function of time after the hydrogen supply was stopped.

  • In the first case, with a Pt anode, the voltage went to zero almost immediately (15 seconds).
  • In the second and in the third, however, when VOx was employed, zero V was observed after a longer time interval. The time depended on the thickness of the VOx layer and the current density; a maximum of 210 seconds was observed.

In the image above, the area marked (b) shows the evolution of the voltage over time for the three cases.

Alternative Energy Source: Important Results

This study was a major breakthrough in the search for alternative energy sources. As Dr. Van Overmeere told Decoded Science, “These results show that, in principle, it is possible to store charge in a TF-SOFC. The VOx acts as a multifunctional material. It allows hydrogen oxidation, which generates the electron flow during the operation with hydrogen. The different vanadium oxidation states and the capability of VOx of storing hydrogen allow current to continue to flow for some time after the H2 supply is stopped.” 

How does this research help the search for alternative energy sources? According to Dr. Van Overmeere, “The performance of this kind TF-SOFC still has to be improved, but these findings give us a clear indication on the way to go, and on which aspects we should concentrate our future investigations.”

Sources

Q. Van Overmeere, et al. Energy Storage in Ultrathin Solid Oxide Fuel Cells. (2012). Nano Letters. dx.doi.org/10.1021/nl301601y. Accessed July 8, 2012.

IEA Energy technology Essential. Fuel Cells. (2012). Accessed July 8, 2012.

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