Thursday, November 24, 2005

Energy Applications of Nanotechnology - Part 4: Carbon Aerogel Composites and Catalysts


It's time for another installment of our 'Energy Applications of Nanotechnology' segment over here at Watthead. Today we take a look at carbon aerogel composites. The technology has been getting a bit of press lately as GreenShift Corporation, a business development corporation that invests in emerging companies and technologies which might enable large environmental gains, has recently invested in Aerogel Composite (ACI), a development-stage company that manufactures meso-porous carbon aerogel composites.

So what are these things and what are they good for? Well, aerogels are solid-state substances similar to gels but in which the liquid phase is replaced with gas. Aerogels have a highly dendritic structure, meaning their structure has many tree-like branches [check out the graphic to get some idea what we're talking about]. This results in a very high surface area and very porous and light material. Aerogels consequentally rank among the world’s lowest density solids.

According to Green Car Congress, their microstructure and physical properties can be manipulated at the nanometer scale by selection of raw material and modification of manufacturing conditions. Aerogel materials can also be produced in a number of forms including monoliths, thin-films, powders, or micro-spheres to respond to given application requirements. According to ACI, incorporation of additives into aerogels results in materials that are called aerogel composites. The role of additives is to enhance the properties of pure aerogels or to impart additional desirable properties depending on the application.

Aerogels have a number of uses and ACI has patented a process for the preparation of aerogel composites destined for a variety of applications, including carbon aerogel-supported catalysts for fuel cells and other metal oxide aerogel-supported catalysts for catalytic converters for combustion engines.

In their use as electro-catalysts, ACI's aerogel composites achieve equivalent catalytic performance while using one half to one tenth the quantity of precious metals like platinum used in current technology. These catalysts are the primary cost drivers in all of the markets ACI is addressing. ACI’s technology directly addresses the cost of fuel cell systems by lowering the platinum cost for the membrane electrode assembly.

For example, according to Green Car Congress, ACI’s Hyrogel Carbon Aerogel Supported Platinum Catalyst reduces the platinum requirements of hydrogen-powered proton exchange membrane (PEM) fuel cells by more than 90% from recently prevailing levels.

The platinum content of PEM fuel cell electrodes is a major hurdle to the commercialization of fuel cells. The industry has long been waiting for technologies, like ACI's aerogels or the metalic nanopowders we considered in our last installment of this segment, that can reduce the need for platinum in their electrodes. These nanotechnology applications could thus have a serious impact on the fuel cell industry.

Additionally, aerogels can be used in catalytic emissions control systems. Here ACI's aerogel-supported platform reduces precious metal loading and therefore cost. Green Car Congress reports that in 2003, the $4 billion market for emission control catalysts utilized $3.19 billion of platinum group metals. This market is expected to grow significantly due to increased regulation, stricter enforcement and rising demand for diesel automobiles in Europe and the U.S. This could therefore be a huge market area for ACI's aerogels.

Other potential applications include materials for ultracapacitor electrodes, hydrogen and energy storage, catalyst for fuel reformers, specific gas sensors, biosensors, and desalination of water.

Resources:

  • Aerogel Composite, LLC

  • Green Car Congress: GreenShift Invests in Aerogel Composites for Fuel Cell and Catalytic Applications


  • Previous Energy Applications of Nanotechnology Installments:
  • Part 1: Quantum Dots and Photovoltaics

  • Part 2: Electron Thermotunneling and the Power Chip

  • Part 3: Nanopowders and Electrodes

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