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The Road to Greener Cities

By Nana Koram / Intern
November 16, 2001

Fuel cell technology has a surprisingly long history-scientists have been digging into its mysteries since 1839-but it finally appears to be moving out of the research laboratory into the marketplace where it is destined to become an important new power source for everything from trucks and buses to computers and cell phones.

In March 1998, Chicago became the first city in the world to run fuel cell-powered buses. These days, tourists in London can explore the city in fuel cell-powered taxis. Several companies are competing to develop fuel-cell-powered bicycles. Only a few years ago, fuel cells cost a prohibitive $5,000 per kilowatt, the equivalent of buying an engine for $250,000, but have now dropped to below $300 per kilowatt. In order to compete with the internal combustion engine (ICE), the price must continue to fall to the $30 per kilowatt range. A number of leaders in the transportation industry are now predicting that fuel cell prices will continue to drop and it will begin to replace the ICE in a number of applications.

If or when the internal combustion engine is relegated to the museum, the benefits will be substantial. Fuel cells are naturally low-emission. Without adding catalytic converters and other emission-reduction devices, fuel-cell vehicles produce less than 10 percent of the air pollution that spews out of the tailpipes of today's automobiles. So they will be good for the environment.

Fuel-cell vehicles will also have a positive impact on the economy. They have about twice the fuel efficiency of comparable internal combustion engines. So, if they gained only a 20 percent share of the domestic auto market, fuel-cell cars would allow the United States to cut its oil imports by 1.5 million barrels per day, thus reducing America's dependency on oil-producing nations.

They are also elegantly simple electrochemical devices that convert chemical energy to electricity with high efficiency and with few moving parts, so their operation and maintenance requirements are minimal. Fuel cells sound almost too good to be true and their amazing potential is one of the reasons why scientists have continued to study them for more than 160 years. It was also what attracted me to the laboratory of Charles Lukehart when I selected a research laboratory for an internship in my Communication of Science, Engineering and Technology major.

Lukehart, a professor of chemistry at Vanderbilt University, is one of a hundreds of scientists who have become intrigued by the challenge of this simple, yet sophisticated system. Although many of the problems that have kept fuel-cell technology from commercial success have already been solved, there is still a need to reduce the initial cost of fuel-cell systems before they can live up to their full potential and Lukehart has spent the last six years attacking this problem.

Lukehart's interest in chemistry started by watching his brother

In person, Lukehart is a tall gentleman with keen eyes, and a surprisingly soft voice. He grew up in a small town in Pennsylvania and first developed an interest in chemistry by watching his older brother working in a makeshift chemistry lab in the basement of their home. David Lukehart, now an industrial engineer, would regularly collect lead bullets from practice ranges and melt them down, shaping the molten metal into whatever he fancied at that particular moment. Being the younger brother, Lukehart was banned from touching anything in his older brother's lab. Somehow, this prohibition fed the younger Lukehart's fascination with chemistry, and guided him to a career as a chemist. As a result, he graduated from Pennsylvania State University in 1968 with a B.S. in chemistry.

In the process, Lukehart decided that he preferred inorganic over organic chemistry because he was attracted to the diverse compositions and interesting colors of inorganic compounds. He then went on to the Massachusetts Institute of Technology (MIT) where he obtained his doctorate in inorganic chemistry in 1972. The following year he married Marilyn McKinney, a pharmacist whose work involves mainly organic chemistry, and with whom he now has three children.

Despite the fact that they both relate to chemistry, they have trouble discussing their work. That is because the different branches of chemistry, like those in many other scientific fields, are becoming increasingly specialized, making it increasing difficult for outsiders to understand what is going on.

All about Eve

Lukehart has two doctoral students working with him on fuel cells. As a research intern, I had the opportunity of working closely with Eve Steigerwalt, who is originally from Germany. She is about 5 feet 3 inches tall, with short dark brown hair and a welcoming smile. She says that she majored in chemistry simply because "I was good at it." She got her best grades in chemistry so her parents encouraged her to stick with it. But it wasn't until she was a university undergraduate that Steigerwalt discovered that she actually liked the subject! After graduating from University of Virginia in 1994, Steigerwalt decided to continue her studies in the field she had grown to love and she chose Vanderbilt for graduate study.

It was Steigerwalt who introduced me to the inner workings of the fuel cell. It is very simple. Two separate electrochemical reactions occur in fuel cells: an oxidation half-reaction occurring at the anode and a reduction half-reaction occurring at the cathode. Each half-reaction requires the use of a catalyst to increase its rate. The catalyst that works best on both half-reactions is platinum, a very expensive metal.

The research in Lukehart's lab is focused on improving the efficiency of direct methanol fuel cells. There are two basic kinds of fuel cells currently under development: those that use hydrogen for fuel and those than use methanol. Hydrogen fuel cell technology is more advanced. Hydrogen fuel cells were used to power the Apollo spacecraft and provide electricity for the space shuttle. This type of fuel cell also has the benefit of operating with zero emissions: Its only byproduct is water. On the other hand, hydrogen is a difficult fuel to handle and hydrogen fuel cells can explode if they malfunction. Methanol is much easier to handle and not nearly as explosive as hydrogen, but methanol fuel cells are not quite as clean, producing about a tenth of the emissions as a comparable ICE.

Direct methanol fuel cell

A direct methanol fuel cell, as the name suggests, runs on methanol. Inside the cell, a catalyst made of platinum (Pt) and ruthenium (Ru) metals catalyzes or speeds up the conversion of the chemical energy from the methanol to electrical energy. Since platinum is so expensive, a natural approach to reducing cost is to use as little platinum as possible. Unfortunately, when the amount of platinum is reduced, the catalyst's performance also drops to a point where the methanol fuel cell becomes completely impractical. So Lukehart decided to explore ways to boost the efficiency of the catalyst without increasing the amount of platinum used in its production.

Making an effective catalyst is a four step process: First, you create material that consists of molecules that each contain one atom of platinum and one atom of ruthenium. Next, you convert this material into a nanocomposite. Then you characterize the nanocomposite that you have prepared so that you have some idea how it came out. Finally, you determine its effectiveness by putting it in a small bench version of a fuel cell and measure how much electrical power it produces.

Watching Dr Lukehart build a test fuel cell was both fascinating and surprising. I somehow expected a fuel cell to be a very high-tech, complicated-looking piece of equipment. But he built it out of very simple materials: copper wire, glue, water and a special type of thin, flat conductor easily obtained in a chemical store. A voltmeter was clipped on to measure the voltage and an ammeter was attached to measure the current that the cell produced. The end result was about the size of my thumb and looked like something even I could have put together.

Creating my own catalyst

The highlight of my internship was creating my own catalyst.

To make a material with molecules that consist of just one ruthenium and one platinum atom I had to first create a ruthenium dimer, molecules that consist of two linked ruthenium atoms. The lab had platinum dimer on hand, purchased from a chemical supply store. So I didn't have to make that as well. But I did have to combine the two to form molecules of platinum-ruthenium dimer. This part of the experiment proved to be rather boring and tedious. After making my first batch of Pt/Ru dimer, I put a sample in a Nuclear Magnetic Resonance (NMR) machine to analyze it. Unfortunately, my NMR spectrum showed some unexpected features, suggesting that the result of my synthesis was not pure. Eve was very encouraging and assured me that this was a common part of the research process. However, it meant that I had to start the synthesis process all over again.

The next step, making my dimer into a nanocomposite, went quite smoothly. To begin with, I combined the Pt/Ru dimer with carbon powder in a series of steps called multi-deposition. I divided the Pt/Ru compound into three parts and each part was combined with the carbon particles separately. Eve explained that it was done this way to ensure that all of the Pt/Ru molecules combined with the carbon. Then, using a microwave oven, the material was heated to complete the process of creating the nanocomposite. When the material was being heated, the carbon particles became red hot. Watching the carbon sparks through the microwave window reminded me of fireworks. However, the process is very long and drawn out and became slightly boring after the first couple of weeks.

In the characterization step, I was introduced to the X-ray diffraction machine, which measured the size of the particles in my nanocomposite and confirmed the composition of the nanocrystals that had formed. The smaller and more separate the crystals, the more efficient the catalyst would be. Electron microscope images indicated that the crystals in my material were small and a number of them had fused together instead of remaining separate. This was very disappointing because I had worked extremely hard for several weeks to create them. Now I was faced with the possibility that my final catalyst would not work as efficiently as I had hoped. But there was nothing to do except move on to the next step.

The final step in the process was to put the catalyst into the makeshift fuel cell and test its efficiency. The greater the voltage and the higher the current produced, the more effective the catalyst. Unfortunately, due to the fusing of the crystals formed in my nanocomposite, the current I obtained from my fuel cell was low, indicating that my catalyst was not working fast enough.. I was a little disappointed that my catalyst was not as powerful as it should have been, but the fact that it worked at all made me really happy. I felt like a real chemist!

Venturing into the unknown

Working in a research lab is nothing at all like working in a class lab. With a class lab, the results of the experiment are always known. For example, in my organic chemistry labs, we learned about different reactions in lectures and our labs consisted mainly of performing these reactions. We always had the textbook to alert us when something was going wrong. For example, the textbook would let us know that a blue compound should be formed at the end of the first half of the reaction. So, if you did not obtain a blue compound, you knew that something was wrong and that you may need to restart the experiment.

In a research lab, by contrast, there are no textbooks to warn you when you are going wrong. Most of the experiments done in research labs have never been done before. Research is sometimes a trial and error process, and you do not always know if you are doing something wrong until you get to the end of the experiment. Even though researchers can double check the compounds they make at each step using sophisticated instruments like NMR or X-ray diffraction machines they don't know how successful the experiment has been until the very end. It's a bit like groping around in the dark in an unfamiliar room. You can't see what is ahead of you or if you're going in the right direction. You just have to keep on trying until you make it to your destination.

A final lesson

The most important lesson I stumbled upon while working with the Lukehart group is that research is a long process. Major discoveries do not happen overnight. Research work can take years to complete but it is often worthwhile in the end. Scientists have a genuine thirst for knowledge that keeps them going even in the dark and they consider finding the answers to puzzling questions to be one of the best rewards for their work.

Prof. Lukehart's home page
http://www.vanderbilt.edu/AnS/Chemistry/chemmain/lukehart.html


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