Wednesday, December 18, 2013
Viswanathan's Fuel Cell Research Leads to Breakthrough in ElectrocatalysisDirect observation of a working fuel cell leads to a surprising new route for enhanced catalysis
As reported in Nature Communications, Assistant Professor Venkat Viswanathan (starting at CMU, Fall 2014) along with his former colleagues at SLAC National Accelerator Laboratory and Stanford University have postulated an alternate route for a fuel cell to make a water molecule.
Fuel cells are electrochemical devices that convert chemical energy into electricity. The bottleneck for the wide-spread adoption of fuel cells has been the costly platinum which is required to catalyze the reaction of oxygen to water. A key challenge is to reduce the amount of platinum required to catalyze this reaction.
Based on many years of work, theorists at SUNCAT Center for Interface Science and Catalysis under the direction of Jens Nørskov have developed a detailed atomistic picture for this reaction. It has been demonstrated that the main culprit for the sluggishness of this reaction is related to hydroxide on the surface. In the beginning of last year, Venkat Viswanathan along with Heine Hansen, found that a subtle variation induced by changing the voltage could lead to the formation of two different kinds of hydroxide on the surface. One type of hydroxide is "hydrated," or loosely bonded with water molecules, while the other is not.
Using a revolutionary new technique called ambient pressure photoelectron spectroscopy (APPES) at Stanford Synchrotron Radiation Lightsource, Hirohito Ogasawara and his colleagues were able to watch the reactions of a fuel cell as they occurred on the surface of a platinum catalyst. This allowed a way to observe this subtle hydration effect, visible only with APPES.
Hernan Sanchez Casalongue, a graduate student in the chemistry department at Stanford University, built a miniature fuel cell used to observe the reactions under operation. He said, "At first what was new was the technique, and it was working. But as we analyzed our results, we realized that indeed there were two different kinds of hydroxide on the surface" This prompted the theorists, Venkat Viswanathan and Heine Hansen, to dig deeper on the role of hydration. They found that the non-hydrated hydroxide requires less energy to take the final step to H2O compared to the hydrated hydroxide.
Anders Nilsson, deputy director at SUNCAT and Hirohito Ogasawara believe this insight is a breakthrough in electrocatalysis. However, they admit that it is not yet clear how much energy boost could be obtained based on this insight.
Venkat Viswanathan believes that tuning hydration could play a crucial role in enhancing processes for a wide range of chemical transformations. He intends to pursue these efforts by testing these ideas with the aid of his colleagues at Carnegie Mellon University, Shawn Litster, Jay Whitacre and John Kitchin.
Read the SLAC National Accelerator Laboratory press release here