Japanese Scientists Explain Quantum Effects in Fuel Cells
A group of researchers led by Kasai Hideaki, a professor in the Graduate School of Engineering at Osaka University, described the mechanism behind the quantum reactions in polymer electrolyte fuel cells (PEFC). They have also created a method to effectively model and design PEFC using computational materials design techniques.
PEFCs, or proton exchange membrane fuel cells, are a type of fuel cell being developed for transport applications as well as for stationary fuel cell applications and portable fuel cell applications. Their distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a special polymer electrolyte membrane. They are a leading candidate to replace the aging alkaline fuel cell technology, which was used in the Space Shuttle.
Such fuel cell consists of a fuel electrode, a solid polymer membrane, and an air electrode. A proton exchange membrane fuel cell transforms the chemical energy liberated during the electrochemical reaction of hydrogen and oxygen to electrical energy, as opposed to the direct combustion of hydrogen and oxygen gases to produce thermal energy. A stream of hydrogen is delivered to the anode side of the membrane electrode assembly. At the anode side it is catalytically split into protons and electrons.
Professor Kasai group has found that the dissociative adsorption of hydrogen molecules on metal surfaces involves the quantum tunneling effect. As an example of intellectual design, they used metal surface (Aluminium, etc.) coated with platinum with a larger lattice constant than the pure platinum as an anode catalyst. This result shows that the platinum-coated surface, having extensional strains, not only promotes dissociative adsorption of hydrogen molecules but also suppresses carbon monoxide poisoning.
Also, they found out that quantum effects play a significant role in the dissociative adsorption mechanism of oxygen molecules. They used Pt/Fe catalyst as cathode; in which two atomic layers of platinum are deposited on Fe(001) surface. It was observed that the induced magnetization of the surface Pt atoms efficiently allow the dissociative adsorption of oxygen molecules.
The mechanism of the reaction in the polymer membrane, specifically the interaction of positive hydrogen ion with H2O to form H3O+ in the Nafion chain, also involves quantum effects.
Arevalo, R., Escaño, M., & Kasai, H. (2013). Computational Mechanistic Study of Borohydride Electrochemical Oxidation on AuNi(111)The Journal of Physical Chemistry C, 117 (8), 3818-3825 DOI: 10.1021/jp311904k