Squeezing boosts platinum catalyst activity

CHEMISTS at Stanford University, US, have discovered that ‘squeezing’ platinum catalysts by just 0.01 nm can increase their catalytic efficiency by 90%.

The technique could be used to improve the performance of fuel cells, increasing their energy output, or platinum-based electrolysers which split water into oxygen and hydrogen fuel, as well as other clean technologies. Haotian Wang, who led the research, said that the technique is a new way to fine tune metal catalysts, and uses ordinary battery materials.

Wang and the team used lithium cobalt oxide, which is a common material in the lithium batteries found in electronic devices like smartphones and laptops. When electricity is applied to the material, it expands by 0.01 nm, but when the electricity is discharged, it contracts again. It is this contraction that the researchers took advantage of.

“The electronic structure of a catalyst needs to match the molecule of interest in order to achieve the chemical reaction you want. You can adjust the electronic structure of a catalyst by compressing the atoms or pulling them apart,” said Wang.

The researchers stacked multiple layers of lithium cobalt oxide to create an electrode, then added several layers of platinum to act as a catalyst. The platinum expands and contracts with the lithium cobalt oxide when electricity is passed through it. The team tested the platinum-coated lithium cobalt oxide in the oxygen reduction reaction that takes place in fuel cells. When in the compressed state, the platinum was 90% more effective than ordinary platinum at reducing oxygen. When in the expanded state, the platinum was 40% less effective.

“Our technology offers a very powerful way to controllably tune catalytic behaviour. Now, mediocre catalysts can become good, and good catalysts can become excellent,” said Yi Cui, a materials science and engineering professor at Stanford and one of the researchers.

Wang adds that this technique of controlling platinum’s activity may also be applicable to other metal catalysts.

Science DOI: 10/btv5