Simulations by scientists at Purdue University have unraveled the mystery of a new electrocatalyst that could solve a significant problem associated with fuel cells and electrolyzers.
Both fuel cells, which use chemical reactions to produce energy, and electrolyzers, which convert energy into hydrogen or other gases, employ electrocatalysts to promote the necessary chemical reactions. Electrocatalysts that can activate such reactions tend to be unstable, however, because they corrode in the highly acidic or basic water solutions that are used in fuel cells and electrolyzers.
A team led by Jeffrey Greeley, an associate professor of chemical engineering at Purdue University, has now identified the structure for a novel electrocatalyst made of nickel nano-islands deposited on platinum that is both active and stable. This design conferred properties on the nickel that Greeley said were unexpected but highly beneficial. The team report their findings in a paper in Nature Energy.
"The reactions led to very stable structures that we would not predict by just looking at the properties of nickel," Greeley said. "It turned out to be quite a surprise."
"The reactions led to very stable structures that we would not predict by just looking at the properties of nickel. It turned out to be quite a surprise."Jeffrey Greeley, Purdue University
Greeley's team, together with collaborators working at Argonne National Laboratory, had noticed that nickel placed on a platinum substrate showed potential as an electrocatalyst. Greeley's lab then proceeded to work out how an electrocatalyst with this composition could be both active and stable.
Greeley's team simulated different thicknesses and diameters of nickel on platinum, as well as voltages and pH levels in the fuel cells. Depositing nickel just one or two atomic layers in thickness and one or two nanometers in diameter created the conditions they wanted. "They're like little islands of nickel sitting on a sea of platinum," Greeley said.
The ultra-thin layer of nickel is key, because all the electrochemical activity occurs at the point where the two metals come together. And since there are only one or two atomic layers of nickel, almost all of it is reacting with the platinum. That not only produces the required catalytic activity, but changes the nickel in a way that keeps it from oxidizing, providing the stability.
Their collaborators at Argonne then analyzed this nickel-platinum structure and confirmed the properties Greeley and his team expected the electrocatalyst to have.
Next, Greeley plans to test similar structures with different metals, such as replacing platinum with gold or the nickel with cobalt, as well as modifying the pH and voltages. He believes other more stable and active combinations may be found using his computational analysis.
This story is adapted from material from Purdue University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.