Gold standard for catalysts

Scientists at the US Department of Energy’s Brookhaven National Laboratory have discovered that adding gold clusters to platinum fuel cell catalysts prevents them from dissolving.

Platinum is the most efficient electrocatalyst for accelerating chemical reactions in fuel cells for electric vehicles, but during stop-and-go driving, the platinum dissolves, which reduces its efficiency as a catalyst. A platinum cathode electrocatalyst can shrink by as much as 45 per cent over five days.

Under lab conditions that imitate normal fuel cell use, the Brookhaven researchers added gold clusters to the platinum electrocatalyst, which kept it intact during an accelerated stability test. This test was conducted under conditions similar to those encountered in stop-and-go driving in an electric car.

The researchers displaced a single layer of copper with gold on carbon-supported platinum nanoparticles. After being subjected to several sweeps of 1.2 volts, the gold monolayer transformed into three-dimensional clusters.

Using x-rays as probes at Brookhaven’s National Synchrotron Light Source, a scanning transmission microscope at Brookhaven’s Centre for Functional Nanomaterials, and electrochemical techniques in the laboratory, the scientists were able to verify the reduced oxidation of platinum and to determine the structure of the resulting platinum electrocatalyst with gold clusters, which helped them to gain an understanding of the effects of the gold clusters.

In the Brookhaven experiment, the platinum electrocatalyst remained stable with potential cycling between 0.6 and 1.1 volts in over 30,000 oxidation-reduction cycles, imitating the conditions of stop-and-go driving.

The next step for the researchers will be to attempt to duplicate the results in real fuel cells.