In-situ observation of plasmon-controlled photocatalytic dehydrogenation of individual palladium nanoparticles

Abstract

Plasmonic nanoparticle catalysts offer improved light absorption and carrier transport compared to traditional photocatalysts. However, it remains unclear how plasmonic excitation affects multi-step reaction kinetics and promotes site-selectivity. Here, we visualize a plasmon-induced reaction at the sub-nanoparticle level in-situ and in real-time. Using an environmental transmission electron microscope combined with light excitation, we study the photocatalytic dehydrogenation of individual palladium nanocubes coupled to gold nanoparticles with sub-2 nanometer spatial resolution. We find that plasmons increase the rate of distinct reaction steps with unique time constants; enable reaction nucleation at specific sites closest to the electromagnetic hot spots; and appear to open a new reaction pathway that is not observed without illumination. These effects are explained by plasmon-mediated population of excited-state hybridized palladium-hydrogen orbitals. Our results help elucidate the role of plasmons in light-driven photochemical transformations, en-route to design of site-selective and product-specific photocatalysts.

Thermal effects – an alternative mechanism for plasmon-assisted photocatalysis

“…This suggests that the inhomogeneities must be minimized in order to allow the distinction between thermal and non-thermal effects. This can be achieved by using thinner pellets, or ultimately, by studying a single particle [46][47][48][49].…”

Bimetallic nanostructures: combining plasmonic and catalytic metals for photocatalysis

“…This coupling increases when the antenna and reactor LSPRs are spectrally close, the reactor placement breaks the antenna's symmetry, and/or interparticle spacing is reduced [25,50]. The resulting LSPR is spectrally similar to the plasmon resonance of the antenna itself, though usually slightly shifted [25,27,28]. Spatially, the enhanced electromagnetic fields are either highly localized to the interparticle gap or at the reactor surface, creating a plasmonic hot spot.…”

“…Bimetallic nanoparticle catalysts combine these two metals, with an ideal photocatalyst retaining the optical behavior of the plasmonic metal and the reactive behavior of the catalytic metal. Indeed, in recent years, bimetallic catalysts have demonstrated increased reaction rates [19][20][21][22][23], optical sensitivity [24][25][26][27], and product selectivity [28,29] for a greater variety of reactions than their monometallic counterparts due to the larger number of molecular adsorbants that interact with catalytic metals. While 'bimetallic' technically encompasses any combination of two metals [30] (i.e.…”

The Light Years: Combined optical and environmental electron microscopy to visualize photonic processes with atomic-scale resolution

“…Finally, reaction nucleation occurs more often at electromagnetic hot-spots. Our results help elucidate the role of plasmons in light-driven phase transformations, en-route to design of siteselective and product-specific photocatalysts [1][2][3].…”