Diamonds Are a Fuel Cell's Best Friend

Roland Piquepaille writes "Researchers at UC Davis have used nanocrystals made of diamond-like cubic zirconia to develop cooler fuel cells. Even if hydrogen fuel cells have been touted as clean energy sources, current fuel cells have to run at high temperatures of up to 1,000 C. This new technology will allow fuel cells to run at much lower temperatures, between 50 and 100 C. Obviously, this could lead to a widespread use of fuel cells, which could become a realistic alternative power source for vehicles. The researchers have applied for a patent for their technology, but don't tell when fuel cells based on their work are about to appear."

Comments

Re:Uh-oh

[SatanicPuppy]

It's the other way around actually...CZs are thermal insulators, so they reduce the rate of heat transfer...That's probably one of the key reasons they're being used in this application.

Diamonds, on the other hand, are extremely efficient thermal conductors, so they are quite efficient at heat transfer, making them terribly unsuitable to this sort of application where heat is already the major problem.

So CZ is cheaper, easier to obtain, and (for once) actually has the chemical advantage over the diamond. Cool indeed.

Re:great

[spun]

The surprise proposal was invented by De Beers. They polled woman and found out that most women, when asked by their partners, would say they would rather that two months salary went to a down payment on a house. So De Beers marketing department convinced men that talking about marriage and discussing the proposal was unromantic, and they should simply surprise their intended with a flashy, expensive ring.

Re:Your fuel cell is going to be pissed...

[SatanicPuppy]

No, no they're not. CZ is almost twice as heavy by volume. CZ has a substantially different refractive index...Set C and CZ next to each other and examine, and the difference should be clear to even a half-trained eye. CZ doesn't conduct heat well and C does very well. And finally, C will scratch CZ, but CZ will not scratch C.

They may have been hard to tell apart 200 years ago (doubtful), but there is no way a competent gemologist could make that mistake today.

Re:fuel cell temperature

[msmikkol]

The press release, which is phenomenally uninformative, fails to mention that the researches are most probably talking about solid oxide fuel cells. SOFCs use yttria stabilized zirconia as their electrolyte, and it conducts oxygen ions only at a high temperature, 800 to 1000 C. That kind of temperature sets severe limits on fuel cell materials, and therefore researcher strive to drive down the operating temperature of SOFCs. Few hundred degrees down and the range of suitable materials grows much larger.

At the moment, the most common fuel cell type in vehicle applications is the polymer electrolyte membrane fuel cell, which operates usually at ca. 80 C. The scientists are trying to develop PEMFCs that would operate at an elevated temperature, ca. 140 to 160 C. There are three main reasons: Higher carbon monoxide tolerance of the Pt catalyst, easier water management (no liquid water) and easier heat management.

Carbon monoxide is present at least in trace amounts in most fuel feed made by reforming hydrocarbons. Elevating the operating temperature to 160 C increases the CO tolerance from some ppm to few per cent. Conventional PEMFCs need liquid water to remain operational, but excess water obstructs reactant transfer and decreases performance. If liquid water is present in the cell, good water management is both paramount to high performance and pretty tricky.

An average fuel cell power source in a passenger car will probably have an electric power of 30-70 kW, and produce the same amount of power in heat. If the fuel cell stack operates at 80 C and you are driving in, say Death Valley, ambient temperature 45 C, you'd need a radiator size of a refridgerator to expulse that amount of heat. Operating the fuel cell stack at 160 C would alleviate that problem in a notable way.