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Driving energetically unfavorable dehydrogenation dynamics with plasmonics

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Science  15 Jan 2021:
Vol. 371, Issue 6526, pp. 280-283
DOI: 10.1126/science.abd2847

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Coaxing unreactive sites

Optical excitation of localized surface plasmon resonances can confine light and create electromagnetic (EM) “hotspots” that can increase catalytic reaction rates. Sytwu et al. show how optical excited plasmons can also control the location of the active site. A crossed-bar gold-palladium hydride (Au-PdHx) plasmonic antenna-reactor system localized EM radiation away from the more reactive PdHx tips. Using in situ environmental transmission electron microscopy, the authors show that changing the illumination wavelength and intensity, along with the surrounding hydrogen gas pressure, could shift dehydrogenation away from the sharp PdHx nanorod tips to the flat middle faces.

Science, this issue p. 280

Abstract

Nanoparticle surface structure and geometry generally dictate where chemical transformations occur, with higher chemical activity at sites with lower activation energies. Here, we show how optical excitation of plasmons enables spatially modified phase transformations, activating otherwise energetically unfavorable sites. We have designed a crossed-bar Au-PdHx antenna-reactor system that localizes electromagnetic enhancement away from the innately reactive PdHx nanorod tips. Using optically coupled in situ environmental transmission electron microscopy, we track the dehydrogenation of individual antenna-reactor pairs with varying optical illumination intensity, wavelength, and hydrogen pressure. Our in situ experiments show that plasmons enable new catalytic sites, including dehydrogenation at the nanorod faces. Molecular dynamics simulations confirm that these new nucleation sites are energetically unfavorable in equilibrium and only accessible through tailored plasmonic excitation.

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