Imaging approach maps fleeting intermediates in hydrogen electrocatalysis

Electrocatalytic transformations not solely require electrical vitality—in addition they want a dependable intermediary to spark the specified chemical response. Surface metal-hydrogen intermediates can successfully produce value-added chemical compounds and vitality conversion, however, given their low focus and fleeting lifespan, they’re troublesome to characterize or research in depth, particularly on the nanoscale.

Now, Cornell researchers have used single-molecule super-resolution response imaging to achieve a clearer view of what occurs, and the place, in floor metal-hydrogen intermediates—insights that would assist enhance hydrogen manufacturing and decontamination of aqueous pollution.

The analysis was published in Nature Catalysis. The paper’s lead writer is former postdoctoral researcher Wenjie Li. The undertaking was led by Peng Chen, the Peter J.W. Debye Professor of Chemistry within the College of Arts and Sciences.

To parse the habits of the intermediates, the researchers chosen palladium-hydrogen as a mannequin system. The imaging course of concerned the introduction of a molecule that probed a person palladium nanocube and reacted with the palladium-hydrogen intermediates on its floor, producing one other molecule, which is fluorescent.

“That fluorescence allows us to image it at the individual molecule level, so we can see every single probe reaction product. And not only can we see at a single molecule level, we can also pinpoint its position with a nanometer spatial precision,” Chen stated.

The imaging revealed that particular person palladium particles had numerous hydrogenation behaviors and properties. In addition, the workforce found that intermediates can kind at completely different websites on the identical particle and due to this fact exhibit completely different behaviors.

“Another important thing we see is that once this hydrogen intermediate is formed on the palladium catalyst, now it turns out the hydrogen atom on the palladium surface is not what you call a static object,” Chen stated. “The hydrogen can move around, not only on palladium particles, but also moving off to the surrounding electro surface.”

This course of, hydrogen spillover, is well-known, however till now, researchers haven’t visualized how far the spillover can attain. The workforce’s probing molecule enabled them to measure this distance and map its location, which was greater than a whole lot of nanometers away.

Typically, to review metal-hydrogen intermediates, researchers depend on “ensemble-averaged methods,” whereby the formation of intermediates is measured in bulk. Using what’s referred to as a Gaussian-broadening kinetic evaluation, the researchers decided that these strategies, whereas helpful, have inherent shortcomings, notably overestimating the steadiness of the intermediates and sometimes masking the particle-to-particle and site-to-site variations.

“In our measurement, we can differentiate particles. We also have a way to estimate the differences between sites on the same particle,” Chen stated. “Now, with this capability, we can more reliably determine the reduction potential that leads to the formation of this palladium-hydrogen intermediate.”

The generality of the workforce’s method may result in probing a variety of electrochemical intermediates. It may very well be significantly priceless for utilizing electrocatalysis in hydrogen technology and detoxifying aqueous environments of pollution similar to chlorinated compounds.