June 22nd, 2012
Econintersect: One of the largest cost components in fuel cells is the platinum catalyst which is required to make the reaction of hydrogen and oxygen proceed at a rate fast enough to be a practical source of electrical energy. Engineers at the University of Wisconsin-Milwaukee (UWM) have identified a catalyst that provides the same level of efficiency in a special kind of device known as microbial fuel cells (MFCs) as the currently used platinum catalyst, but at 5% of the cost. MFCs are a type of fuel cell that generate electricity from water containing organic matter. One obvious application is the use of waste water to generate electricity. Think of the process as a real crappy way to generate electricity. Click on graphic for larger image.
On the anode electrode of an MFC, colonies of bacteria feed on organic matter, releasing electrons that create a current as they break down the waste. On the cathode side, the most important reaction in MFCs is the oxygen reduction reaction (ORR). Platinum speeds this slow reaction, increasing efficiency of the cell, but it is expensive.
The new material—nitrogen-enriched iron-carbon nanorods— did a better job than the graphene-based catalyst material that had previously been considered the best alternative candidate, but it was still not as efficient as platinum. The research presented has not been specific about the cost and efficiency trade-offs.
UWM Professor Junhong Chen has led the project and is testing the nanorods with Assistant Professor Zhen He. Chen was quoted by R&D Magazine:
The nanorods have been proved stable and are scalable, says Chen, but more investigation is needed to determine how easily they can be mass-produced. More study is also required to determine the exact interaction responsible for the nanorods’ performance.
The new cathode material can also be used in MEC devices (microbial electrolysis cells) which are used to create hydrogen from organic matter in situations where energy storage (as hydrogen) is desired for reaction to produce electricity later and/or at different locations from the waste treatment process.
The total cost of MFCs has been 60% from the cost of the platinum. The new device will have cost reduced to less than 45% of the current level by replacing the platinum and further significant cost reduction with process scaling is now more likely.
The work was published in the June issue of the journal Nano Energy. Here is the abstract:
Hydrogen production in microbial electrolysis cells (MECs) is a promising approach for harvesting valuable energy products from organic wastes. Catalysts for proton reduction play a central role in decreasing energy input and increasing hydrogen production rates. Here, a novel nitrogen-containing core–shell-structured catalyst N–Fe/Fe3C@C was prepared and used to modify cathode electrodes in an MEC. The new catalyst consists of iron-based composite (Fe/Fe3C) nanorods as the core and graphite carbon as the shell. The performance of hydrogen production and catalyst stability were investigated. The new catalyst significantly improved hydrogen production compared with unmodified cathode and carbon nanotubes. Although not as efficient as platinum catalysts, a great advantage of the N–Fe/Fe3C@C is its extremely low material cost (less than 5% of the Pt/C catalyst), suggesting its promise for large-scale MEC applications.
- Bringing down the cost of fuel cells (R&D Magazine, 22 June 2012)
- Bringing down the cost of fuel cells/ (Laura M. Hunt, Today @ UWM, 22 June 2012)
- Carbon/iron-based nanorod catalysts for hydrogen production in microbial electrolysis cells (Li Xiao, Zhenhai Wen, Suqin Ci, Junhong Chen, Zhen He, Nano Energy, 12 June 2012)