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Nitrogen Doped Carbon Nanotubes Make Fuel Cells Compete with Gasoline Engines


nitrogen-doped-carbon-nanotubeFor being able to compete with gasoline engines, electric cars must have well-developed energy sources, or better said, better energy storage options, such as batteries. But sometimes batteries aren’t the most appealing option, because, for the moment at least, they’re made of lithium, lead or nickel, which makes them not so very environmentally friendly. Still, the good thing about electric cars is that their engines don’t care where you take the energy from, so one of the problems is solved, if you have efficient electric motors and their auxiliary control systems.

Hydrogen is the most looked for energy storage, but using it is very expensive due to the fuel cell – the device that has to convert the hydrogen into energy, with its only output pure water. Because fuel cells use a platinum based material to work, they are very expensive – about $4,000 for powering a normal passenger car. Solutions are being searched for making fuel cells cheaper, more efficient and more durable, with millions of dollars poured in every year.

Researchers from the University of Dayton, Ohio, led by Liming Dai, have discovered that aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as an efficient metal-free electrode in a fuel cell. They can successfully replace existing platinum-based catalysts, having a much better electrocatalytic activity, long-term operation stability. They are also insensible to CO impurities in the hydrogen, thing that platinum electrodes can’t brag with. The crossover effect (the passing of hydrogen from one part of the fuel cell to another without creating energy) is also greatly diminished.

The scientists group found out that their VA-NCNTs could catalyze a four-electron ORR (oxygen reduction reaction) process with a much higher electrocatalytic, lower overpotential (the difference between thermodynamic and formal potentials), smaller crossover effect, and better long-term operation stability than that of commercially available or similar platinum-based electrodes in alkaline electrolytes.

“In air-saturated 0.1 molar potassium hydroxide, we observed a steady-state output potential of -80 millivolts and a current density of 4.1 milliamps per square centimeter at -0.22 volts, compared with -85 millivolts and 1.1 milliamps per square centimeter at -0.20 volts for a platinum-carbon electrode. The incorporation of electron-accepting nitrogen atoms in the conjugated nanotube carbon plane appears to impart a relatively high positive charge density on adjacent carbon atoms. This effect, coupled with aligning the NCNTs, provides a four-electron pathway for the ORR on VA-NCNTs with a superb performance.”

Needless to say, of course this research has been in cooperation with the US Airforce Laboratory, that probably funded a big part of this research. Platinum-based fuel cells were developed in the 1960s for the space mission, and that’s why using them hasn’t been much of a problem until exporting them in the civilian world. Let’s hope that the delay won’t be so big this time.

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