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Plasmonic Au/p-GaN photocathodes for artificial photosynthesis: Ultrafast hot-carrier dynamics and photoelectrochemical CO_2 reduction

DuChene, Joseph and Tagliabue, Giulia and Abdellah, Mohamed and Habib, Adella and Gosztola, David J. and Cheng, Wen-Hui and Sundararaman, Ravishankar and Sá, Jacinto and Atwater, Harry (2019) Plasmonic Au/p-GaN photocathodes for artificial photosynthesis: Ultrafast hot-carrier dynamics and photoelectrochemical CO_2 reduction. In: 257th ACS National Meeting & Exposition, 31 March-4 April 2019, Orlando, FL.

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Plasmonic-metal nanostructures offer unique opportunities for solar photocatalysis via photo-excitation of highly energetic "hot" carriers at both metal-semiconductor and metal-electrolyte interfaces that can drive photochem. reactions. While examples of hot-electron-driven processes have been widely reported, little is known about the nature of plasmon-derived hot holes and their role in hot-carrier photocatalysis. Here, we report the demonstration of plasmonic Au/p-type GaN photocathodes for photoelectrochem. CO_2 redn. Despite an interfacial Schottky barrier to hot hole transport of more than 1 eV across the Au/p-GaN heterojunction, plasmonic Au/p-GaN photocathodes exhibit photoelectrochem. properties consistent with the injection of hot holes into GaN upon plasmon excitation of Au nanoparticles. We further monitored the carrier dynamics of hot-hole injection via ultrafast transient absorption spectroscopy; we obsd. plasmon-induced hot-hole transfer from Au to p-GaN occurs within the 200 fs instrument response of our exptl. setup, placing hothole transfer from a plasmonic metal to a p-type semiconductor on similar timescales as hot-electron transfer to an n-type semiconductor. Moreover, the ultrafast (t < 200 fs) injection of hot-holes into p-GaN exerts a profound influence on the dynamics of hot electrons left behind on the Au nanoparticles, lowering the electronic temp. and reducing the electron-phonon coupling time. The plasmonic Au/p-GaN photocathodes were further employed for plasmon-driven CO_2 redn. in aq. electrolytes, demonstrating improved selectivity for CO prodn. over H_2 evolution upon plasmon excitation. Taken together, our results offer new insight into the ultrafast dynamics of plasmon-induced hot holes and demonstrate a photoelectrochem. device for harvesting them to selectively drive solar-to-fuel energy conversion with metal nanostructures.

Item Type:Conference or Workshop Item (Paper)
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URLURL TypeDescription Website
DuChene, Joseph0000-0002-7145-323X
Tagliabue, Giulia0000-0003-4587-728X
Cheng, Wen-Hui0000-0003-3233-4606
Sundararaman, Ravishankar0000-0002-0625-4592
Atwater, Harry0000-0001-9435-0201
Additional Information:© 2019 American Chemical Society.
Record Number:CaltechAUTHORS:20190325-082012006
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94085
Deposited By: Tony Diaz
Deposited On:25 Mar 2019 15:42
Last Modified:24 Nov 2020 23:58

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