FuelCellsWorks

Solid-oxide fuel cells run efficiently on a wide variety of conventional fuels and biofuels, but their high operating temperatures have limited their applications. Many researchers are working on this problem, developing new electrode and electrolyte materials that operate at lower temperatures without compromising performance. Now researchers in Japan have demonstrated a high-performance micro fuel cell that operates at lower temperatures, thanks to a restructured electrode.

Cool fuel: This solid-oxide fuel cell has a power output of one watt at 600 degrees Celsius and is about two millimeters in diameter. Its size and operating temperature could make it a suitable power source for quick-starting portable devices. Credit: Science/AAAS

“The cell is suitable for portable power sources, which require quick start-up,” as well as auxiliary power for automotives, says Toshio Suzuki, a research scientist at Japan’s National Institute of Advanced Industrial Science and Technology. Suzuki led the development of the new fuel cell, which is described today in the journal Science. The cell is tube shaped and about two millimeters in diameter; its power output is about one watt at 600 degrees Celsius. Conventional solid-oxide fuel cells operate at temperatures above 700 degrees.

Solid-oxide fuel cells generate an electrical current by pulling oxygen from the air and using it to oxidize fuel. Oxygen comes through the cathode side, fuel through the anode side; the two react in the electrolyte and form water and carbon dioxide as a waste products, depending on the fuel type. This reaction is more efficient than conventional generators. Solid-oxide fuel cells are also more efficient than the other predominant fuel-cell type, which uses expensive platinum catalysts and a polymer membrane that can become contaminated, and runs only on hydrogen fuel.

Solid-oxide fuel cells are “more flexible, more powerful, and don’t have the problem of getting contaminated,” says Eric Wachsman, director of the Florida Institute for Sustainable Energy and chair of materials science and engineering at the University of Florida. The problem with these devices, says Wachsman, is the operating temperatures. This means a long warm-up time can be required, and you can’t use one in a cellular phone. The high temperatures also cause the battery cell to wear out.

Suzuki’s group created a power source with a lower operating temperature by improving the structure of the anode, where the fuel comes in. The Japanese group used conventional techniques including lithography and etching to make anodes with varying degrees of porosity. The best-performing anode was a very porous structure based on nickel oxide, a conventional material for these electrodes. Suzuki says they chose to use existing materials because their performance over time has been proven. “These are reliable materials for long-term stability, and have a cost advantage compared with other new materials for low-temperature solid-oxide fuel cells,” he explains.

“The performance is no doubt quite good,” says Harry Tuller, professor of ceramics and electronic materials at MIT. “This is a nice systematic study showing the evolutionary impact of demonstrated improvements” in the electrode, he says. However, Tuller cautions that the electrodes and the electrolyte are doped with small amounts of expensive materials, which could add expense to the cells. The anode contains, in addition to nickel oxide, a small amount of the rare element scandium.

Wachsman says that it’s difficult to bring down the operating temperature of these cells without compromising on power output. He’s also working on new solid-oxide fuel-cell electrode structures. Using a different set of materials and a similar approach, Wachsman recently demonstrated a fuel cell with a restructured anode and a new electrolyte for a power output of two watts per square centimeter at 650 degrees. This work is described in the journal Electrochemistry Communications.

Suzuki says his group is in discussions with several companies about commercializing the cells.

By Pike Research
By Jevan Fox

Don’t try to go to hydrocarbon-based membrane developer PolyFuel’s web site. Google will warn you that visiting the site “may harm your computer!” Fitting, as the now-debunked fuel cell company is shutting down.

Just last spring, PolyFuel was awarded $2.5 million from the U.S. Department of Energy, which followed two previous DOE awards. The government’s funding of the company’s development program, along with VC money from Intel Capital, could not keep PolyFuel from ceasing operations, and now seeking a buyer of its assets.

PolyFuel was focused on hydrocarbon membrane technology, developed for direct methanol fuel cells (DMFCs), rather than engineering complete systems. The majority of competing membranes in the sector are fluorocarbon membranes, and the hydrocarbon membrane was tested and showed signs it had half the amount of water flux and one third the methanol crossover as its counterpart. PolyFuel focused its engineering of membranes on the portable electronics industry, specifically laptops, 3G mobile phones, and their military equivalents.

In July 2008, the company announced their prototype power supply for the Lenovo T40 ThinkPad that can provide continuous runtimes with the hot swap of a methanol cartridge. Yet, the Mountain View-based PolyFuel, who was spun out of SRI International in 1999 with great fanfare, has decided to exit the game, as the fuel cell industry continues to struggle.

Yet, portable power fuel cells still have bright days ahead. According to Pike Research’s recent report on the subject, sub-20W fuel cells have significant advantages over conventional batteries, including their extended runtimes and use of clean, renewable fuels. As companies like Medis continue to sell fuel cells on Amazon, customer feedback will increase along with demand, and a displacement of current technology will occur between 2015 and 2017.

What happened to PolyFuel will happen to other companies in the space, as the technology seeks its best applications within the market, and it does not signal an end to the portable power fuel cell, yet illuminates the growing pains of an industry that seems forever young.

Reprinted with permission from Pike Research, a market research and consulting firm that provides in-depth analysis of global clean technology markets.