Sunday, February 8, 2009

UT Austin Center for Electrochemistry Conference

I spent this weekend attending an electrochemistry conference at UT Austin called “Challenges at the Electrode/Electrolyte Interface”. Electrochemistry is involved in a number of systems that could play a role in helping address the world’s energy needs. This includes batteries, fuel cells, and photoelectrochemistry. These systems could play a role in vehicle propulsion via plug-in hybrid, electric, or fuel cell vehicles, load leveling for large scale renewable energy infrastructure via fuel cells or flow batteries, or fuel or electricity production via photoelectrochemical systems such as dye-sensitized solar cells, artificial photosynthesis, or photon driven water electrolysis for hydrogen production.

One of the poorly understood and critical areas of research for fuel cells and other electrochemical systems is electrocatalysis. Despite decades of research, catalysis and what makes certain materials better catalysts than others is still not well understood. (A catalyst is a material that increases the rate of a chemical reaction. Catalysts are required to drive the reactions needed to generate electricity in fuel cells). Much effort is being put into trying to identify other materials to replace the costly platinum catalyst in fuel cells. Some promising alloys include Pd-Co, Pt-Co, and Pt-Cu.

A number of theories exist as to what leads to the improved performance of a Pt-Co (platinum cobalt) alloyed catalyst over a pure Pt catalyst. These theories include bifunctional effects, electronic effects, and geometric effects (the quantum mechanical details of which are way beyond the scope of this blog post). Because these factors all generally act in concert, it becomes very difficult to separate out the contribution of each. Better understanding the relative contributions can aid in the search for better alloyed catalyst materials, a process that currently involves much trial and error over the wide space of potential alloyed material combinations.

Jeff Greeley, who presented at the conference, is trying to help in this process by using quantum mechanical computer modeling to pre-screen for materials that are both active catalysts and stable catalysts (1) . Another researcher, Peter Strasser, finds that by creating particles containing a copper core and a platinum surface layer, catalytic activity can be increased due to increased compressive strain on the surface platinum (2). By controlling the composition, annealing process, and de-alloying process, this strain and corresponding catalytic performance changes can be tuned.

Other cool energy research at the conference included studying the degradation mechanisms of lithium ion batteries and biologically inspired improvements to electrochemical systems. Battery durability is a major concern for automotive applications and an issue that must be resolved for plug-in hybrids to be feasible on a large scale. Laptop batteries generally only last a few years, but that certainly wouldn’t be acceptable for a vehicle which needs to stay running for at least a decade without needing a $10,000+ replacement battery pack. Robert Kostecki investigated battery degradation after repeated cycling and found that degradation mechanisms include loss of conductivity due to both changes to the conductive carbon coating and particle separation in the cathode (3)

It will be interesting to see what happens with the new administration and stimulus spending in terms of funding for energy technology research. Certainly much work still needs to be done at both the basic science level and system design level for a number of electrochemical and other energy systems.

1. Greeley, Jeff, and Jens K. Nørskov. “Large-scale, density functional theory-based screening of alloys for hydrogen evolution.” Surface Science 601.6 (2007): 1590-1598.

2. Strasser, Peter, Shirlaine Koh, and Jeff Greeley. “Voltammetric surface dealloying of Pt bimetallic nanoparticles: an experimental and DFT computational analysis.” Physical Chemistry Chemical Physics 10.25 (2008): 3670-3683.

3. Kerlau, Marie et al. “Studies of local degradation phenomena in composite cathodes for lithium-ion batteries.” Electrochimica Acta 52.17 (2007): 5422-5429.

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