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Iron-based catalyst developed for hydrogen fuel cell – P.N.N.L.

Iron-based catalyst developed for hydrogen fuel cell – P.N.N.L.
Burning hydrogen in a fuel cell generates an electrical current. A new iron-based catalyst might help make those fuel cells less expensive. (Image from P.N.N.L.)

Scientists at the Pacific Northwest National Laboratory have developed the first iron-based catalyst that can convert hydrogen directly to electricity for more affordable fuel cells.

Fuel cells generate electricity out of hydrogen gas by triggering a chemical reaction that breaks the bond between the gas’ two hydrogen molecules, releasing electrons to create an electrical current.

In most fuel cells, the catalyst used to trigger the necessary reaction is platinum or platinum-based.

“A drawback with today’s fuel cells is that the platinum they use is more than a thousand times more expensive than iron,” said chemist R. Morris Bullock, who lead the research.

Mr. Bullock’s team at the Center for Molecular Electrocatalysis has been developing catalysts that use cheaper metals such as nickel and iron.

Along with chemists Tianbiao Liu and Dan DuBois, Mr. Bullock developed their catalyst based on the molecule hydrogenase which uses iron to split hydrogen.

In order to get the results they wanted, the catalyst has to be able to split the hydrogen atom into all of its parts.

One hydrogen molecule is made up of two protons and two electrons and the catalyst would need to separate the protons, sending it away to be caught by a molecule called a proton acceptor. In a fuel cell, this acceptor would be oxygen.

Once the protons are removed, the electrons would move on to the fuel cells electrodes, creating an electric current for power.

The team determined the shape and size of the catalyst and also tested different proton acceptors. With iron in the middle, arms hanging like pendants around the edges, draw out the protons.

With the design down, the team then measures how fast the catalyst could split molecular hydrogen. Their best time was about two molecules per second, thousands of times faster than the closest, non-electricity making iron-based competitor. The catalyst could also efficiently produce energy at around 160 to 220 millivolts, similar in efficiency to most commercially available catalysts.

The team will be continuing to test the catalyst, figuring out how to make the reactions faster and determine the best conditions under which it performs.

The work was supported by the Department of Energy, Office of Science. P.N.N.L is a one of the D.O.E.’s national laboratories; its Center for Molecular Electrocatalysis is one of 46 Energy Frontier Research Centers established by the Office of Science to accelerate basic research in energy. – EcoSeed Staff

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