The latest issue of the journal Angewandte Chemie published a study that reveals a new cheap material that can be used in electrodes of electrochemical cells. The material discovered by a team of Korean and American scientists is based on affordable carbon black and melamine foam.
The high number of catalytically active centers, combined with the high porosity of the material, allows fast mass transport while at the same time tremendously increases the speed of oxygen reduction reaction (ORR) of the cathodes for fuel cells and metal-aired batteries.
This particular reaction of the cathodes is the factor that determines the efficiency of cells. In addition, the catalytic cathode controls the formation of OH ions in alkaline solution.
However, when solids, liquids and gaseous reactants are involved, the speed of mass transport is slower, particularly when discharging with higher current densities, due to high kinetic inhibition.
The team led by Jaephil Cho at the Ulsan National Institute of Science and Technology (Korea) and Meilin Liu at the Georgia Institute of Technology (USA) aimed to develop an alternative to otherwise very expensive catalytically active metal, which, when dispersed onto the carbon black cathodes, can reduce this kinetic inhibition.
Inspired by the structure of tetrapods, typically used to reduce the impact of waves on coastlines and dams, the scientists decided to test melamine foam, which when pyrolyzed and ground, forms microscopic fragments with the shape of these tetrapods.
The foam was treated with iron chloride and conducting pellets of carbon black. The product was then carbonized and extracted with sulfuric acid. What came out of this were nanotetrapods with nanoparticles of carbon black. These have very high surface area, as well as many catalytically active centers and pores that allow fast mass transport.
When the material is used in cathodes they become highly durable and comparable to metal based ones, but much cheaper.
This study sets the beginning of the invention of highly efficient metal-air batteries and fuel cells at a very affordable cost