CMU team joins methanol-powered fuel cell research
Carnegie Mellon is joining the tide of research towards creating a society based on an alternative fuel source. Prashant Kumta, a professor of materials sciences and biomedical engineering, together with his graduate and post-doctoral team is developing tiny fuel cells that use methanol, which could one day provide the fuel for technological appliances. Unlike other alternative fuel research projects, this one focuses on methanol instead of expensive and unstable hydrogen, which is difficult to mass-produce and would be more difficult to integrate into society.
Portable electronic devices, such as cell phones, personal digital assistants and laptop computers, may well become the first widely used consumer items to take advantage of fuel cells. Instead of recharging or replacing batteries in these devices, users may one day simply have to refuel them.
“We are developing a fuel cell system about the size of a cigarette lighter that could be refueled by inserting a small cartridge of methanol. So we are essentially developing a more efficient catalyst,” said Kumta in a Carnegie Mellon press release dated January 27. The methanol micro-scale fuel cells are so small they can be etched into silicon much like a computer chip.
The fuel cell is powered by a combination of methanol and water. When the methanol and water make contact with a catalyst in the fuel cell, they break down into carbon dioxide, positively charged protons, and negatively charged electrons. The protons are attracted by a special membrane that allows them to pass through, while blocking the path of the electrons. The electrons must pass through an external circuit to get around the membrane, creating an electrical current. The fuel cell produces carbon dioxide, which is vented away, and water, which can be recycled to use with additional methanol.
There are many obstacles that must be overcome in order for fuel cells to be commercially viable. Kumta’s team is working on a variety of measures to solve these issues. “We are developing cathode material for direct methanol fuel cell (DMFC) applications. We would like to develop stable support material for the cathode,” said Daiwon Choi, a post-doctoral student in the lab. The cathode is the place where the oxygen and the hydrogen react, and therefore it is very prone to corrosion. The electrode uses a carbon-based supporting group, and the carbon degrades due to reactivity. “We need to come up with stable material that will not degrade,” said Choi.
“My role is to formulate and test different catalyst compositions specifically for the anode side of the fuel cell,” said Nicolaus Rock, a graduate student in the lab. Kumta and his group are developing nanostructural catalyst compositions that exhibit excellent catalytic activity and can also withstand other components of the fuel cell. “The issue is that the catalyst gets poisoned over time — there is less catalyst available to facilitate the fuel cell reaction”.
There are many advantages to a methanol-fuel-based system. For one, it is liquid-based. “Take the current system. It will be easy to adapt and switch over to methanol-based.” Hydrogen fuel would require many more modifications to the current fuel delivery systems in order to accommodate a hydrogen- fueled society.” Also, the fuel cell operates at a lower temperature than other fuel cells. Solid oxide fuel cells, for example, operate at 1000 degrees Celsius, while DMFCs can operate at 100 degrees Celsius.
Choi has been a researcher in the Kumta lab for six years. Until the recent switch to the methanol fuel cell research, they have specialized in chemical synthesis, electrochemical storage and convergence devices, including lithium ion batteries, cathode and anode materials, and supercapacitors. Rock has been a graduate student in the lab for almost three years, and has mostly concentrated on anode materials for lithium ion batteries. He has been working on DMFCs for three and a half months.
Other obstacles that must be overcome before fuel cells can be commercially available include the polymer electrolyte membrane, which is not very efficient. It is only supposed to allow hydrogen to pass through from the anode to the cathode, but some methanol leaks through. Therefore, a sturdier membrane must be developed.
“There are three main aspects to our lab’s DMFC research,” said Rock. “We are focusing on improving the cathode, anode, and electrolyte membrane.”
Fuel cells might be attractive for use in automobiles someday, but for now they remain prohibitively expensive, mainly due to the use of platinum in carbon based electrodes. On the smaller scale of electronics, however, fuel cells may soon make economic sense. That’s because batteries are an incredibly expensive source of power. The cost per kilowatt of battery power is $10,000. An automotive engine produces the equivalent of a kilowatt for a cost of $100. It may be awhile before fuel cells can compete with automotive power, but it is highly plausible to replace batteries.
Toshiba Corp. announced in October 2003 that it is developing a handheld fuel cell that could power a cell phone. Sony and Motorola are among other companies working on their own versions, all of which would convert methanol or ethanol into electricity.