Straining catalyst films boosts water-splitting

Adding stress and strain to the lives of busy researchers hardly sounds like a strategy for improving productivity. It can work wonders for catalysts, however.

A study has revealed that straining catalytic sites in molybdenum disulfide films substantially boosts the reaction rate of a key step in the water-splitting process relative to the rate on unstrained films (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b01377).

Splitting water could provide a nearly limitless supply of hydrogen to run clean-burning fuel cells if a suitable catalyst can be found. Platinum works well, but it’s expensive. In looking elsewhere, researchers have found that low-cost MoS₂ films with microscopic defects catalyze H₂ production. But complete details of the process have remained unknown, impeding further development.

To sort out the kinetics, a team led by Xiaolin Zheng of Stanford University and Allen J. Bard of the University of Texas, Austin, exposed a MoS₂ film to a plasma to induce sulfur vacancies. They draped the defective film over an electrode patterned with an array of gold nanopillars, causing strain in the portions of the film resting on the pillars. By using scanning electrochemical microscopy, the team showed that the strain boosted H₂ evolution by a factor of four.

“This is an elegant study that introduces an effective method for quantifying the effects of mechanical strain in an electrocatalytic reaction,” comments Pennsylvania State University’s Thomas E. Mallouk. In principle, this method could be used to study strain effects in electrolyzers, fuel cells, and solar cells, he says.