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New microscopy technique monitors ion transfer at the nanoscale; a tool to improve fuel cells or metal-air batteries

Platinbeschichtung_460x280
Visualization of platinum coating in fuel cells. The red areas show high ion transfer activity, the turquoise-green elevations represent the nanoparticles. The picture shows that ion transfer is not uniform all over the coating. Picture: Sergei Kalinin Click to enlarge.

A new microscopy technique devised by an international research team involving University of Heidelberg (Germany) mathematician Dr. Francesco Ciucci and scientists from the United States and Ukraine can monitor ion transfer on the nanoscale. A paper on the technique, called “Electrochemical Strain Microscopy” (ESM), is published in the journal Nature Chemistry.

The new technique means that oxygen reduction can now be represented at a resolution of one millionth of a millimeter. The research findings will be used to develop more efficient and powerful hydrogen fuel cells or metal-air batteries.

The efficiency of fuel cells and metal–air batteries is significantly limited by the activation of oxygen reduction and evolution reactions. Despite the well-recognized role of oxygen reaction kinetics on the viability of energy technologies, the governing mechanisms remain elusive and until now have been addressable only by macroscopic studies. This lack of nanoscale understanding precludes optimization of material architecture.

Here, we report direct measurements of oxygen reduction/evolution reactions and oxygen vacancy diffusion on oxygen-ion conductive solid surfaces with sub-10 nm resolution. In electrochemical strain microscopy, the biased scanning probe microscopy tip acts as a moving, electrocatalytically active probe exploring local electrochemical activity. The probe concentrates an electric field in a nanometer-scale volume of material, and bias-induced, picometer-level surface displacements provide information on local electrochemical processes. Systematic mapping of oxygen activity on bare and platinum-functionalized yttria-stabilized zirconia surfaces is demonstrated.

This approach allows direct visualization of the oxygen reduction/evolution reaction activation process at the triple-phase boundary, and can be extended to a broad spectrum of oxygen-conductive and electrocatalytic materials.

—Kumar et al.

The ESM technique is based on a mathematical model, a partial differential equation, that describes the movement of oxygen in various materials. By way of this mathematical description, the measurement data from Electrochemical Strain Microscopy can be visualized on the computer screen.

In the paper, Ciucci and his colleagues applied the technique to a fuel cell. A hydrogen fuel cell consists of two electrodes facing one another and separated by an ion conductor. Electric energy is gained via transfer of ions between the two electrodes. The oxygen in the air reacts with the hydrogen brought in from outside. In this process of oxygen reduction, a catalyst—frequently expensive platinum—plays an essential role as reaction accelerator. In all this, says Ciucci, the oxygen reduction process is the limiting factor in connection with the longevity and efficiency of fuel cells.

To optimize ion transfer between the electrodes, a number of fundamental questions have to be answered. How and where exactly does oxygen reduction occur and how does platinum function as a catalyst? Up to now we have had to do without a suitable instrument for investigating the reaction dynamics involved.

What we have found out from this, is that the catalyst layer of 50-nanometer platinum particles does not allow an equal degree of ion transfer at all points.

—Francesco Ciucci

Resources

  • A. Kumar, F. Ciucci, A.N. Morozovska, S.V. Kalinin and S. Jesse (2011) Measuring oxygen reduction/evolution reactions on the nanoscale. Nature Chemistry 3, 707-713 doi: 10.1038/nchem.1112

Comments

A D

Fuelcells are progressing faster then regular lithium battery. Soon car manufacturers will stop producing battery cars and will build and commercialize fuelcells instead. Almost each week fuelcell gain efficiency at reduced cost. AS fuelcell are already sufficiently powerful these researchs put even more attractiveness to it. Now they start optimizing fuelcell at the nanometer scale. Soon the fuelcell will be put in the pressurized hydrogen tank for almost 100% efficiency at cheap cost without maintenance nor pollution. Ice cars and trucks will be there for another 10-20 years as used vehicles and the price of conventionnal fuel will drop. Many car aficionados will race these old farted ice cars and trucks in demolition derby for fun.

kelly

"Soon car manufacturers will stop producing battery cars and will build and commercialize fuelcells instead." - not at the thirty year traditional six and seven figures per 100 kw of fuel cell power.

Darius

What is rational behind hydrogen FC? Using electricity or high temperature heat to produce hydrogen, pressurize it or liquidize, distribute, and finally fill the tank of $1000 000 price vehicle instead directly fill batteries with electricity?

HarveyD

AD...you may be mostly correct but higher performance, lower cost, post-lithium batteries will be around before the end of the current decade and may give FCs a hard time.

However, FCs may retain a niche market for heavy long range buses, trucks, locomotives, ships and very long range special e-planes etc.

A D

@ HarveyD | December 29, 2011 at 08:27 AM

I will be glad to see the coming of batteries that are better then a fuelcell, probably the solid-state batteries.

HarveyD

A D... many more battery technologies will come up in the next 10 to 20 years. Toyota seems to rely a lot on solid states units for their future EVs. Interesting to see what will be available in 10+ years.

JRP3

EV's are already better than fuel cell vehicles, Tesla Model S for example, cost less, and can recharge from any outlet. There is no infrastructure for fuel cell vehicles, and they are more expensive, neither point likely to change.

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