Be it a battery or a fuel cell, efficient electrodes are the be-all and end-all of every electrochemical cell. In the journal Angewandte Chemie, a team of Korean and American scientists has now introduced a novel material for electrodes based on affordable melamine foam and carbon black.
The high porosity significantly facilitates fast mass transport and a high number of catalytically active centers drastically increase the oxygen-reducing activity of cathodes for fuel cells and metal-air batteries.
The reaction that occurs at the cathodes of fuel cells and metal-air batteries is the electrochemical reduction of oxygen, namely the oxygen reduction reaction (ORR). This reaction is considerably inhibited because of its sluggish rate, and the efficiency of the cells is lower than it could be. The catalytic cathode must ensure that oxygen reacts with water, taking up electrons to form OH- ions in alkaline solution. The problem is that in a complex system involving solid, liquid, and gaseous reactants, transport processes are often too slow and inhibit the process, especially when discharging with higher current densities.
Cathodes made of a porous carbon support (carbon black) on which a catalytically active metal like platinum is finely dispersed can very effectively minimize this kinetic inhibition. However, they are expensive and not very stable, thus making them impractical for widespread application. A 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) thus aimed to develop a more economical alternative.
They were inspired by the tetrapod structure (Greek tetra: four, podes: feet) of breakwaters to synthesize a new highly efficient electrocatalyst. Tetrapods, whose four “feet” are pointed toward the corners of an imaginary tetrahedron, are constructed at the coast as well as near dams and piers to reduce the force of waves crashing against the shore. These structures also provide sanctuary for marine life forms in their many large cavities. When melamine foam is pyrolyzed and ground with a mortar and pestle, it forms microscopic fragments resembling tetrapods.
The scientists treated melamine foam with iron chloride and nitrogen-doped ketjenblack (conducting pellets of carbon black). They carbonized this product and extracted it with sulfuric acid. The resulting nanotetrapods studded with nanoparticles of carbon black have a very high specific surface area, a large number of catalytically active centers (Fe/Fe3C, and CN groups), and many pores that allow for rapid mass transport. Cathodes made of this new electrode material are highly durable and excellent performance, comparable to those of metal-based cathodes – at a much lower price. These may represent a highly promising starting point for a new generation of inexpensive and highly efficient metal-air batteries and fuel cells.
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201207193
Jaephil Cho | Angewandte Chemie
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy