Hot Hole Collection and Photoelectrochemical CO2 Reduction with Plasmonic Au/p-GaN Photocathodes
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Joint Center for Artificial Photosynthesis (JCAP) and Thomas J. Watson Lab. of Applied Physics; Caltech
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Joint Center for Artificial Photosynthesis (JCAP) and Thomas J. Watson Lab. of Applied Physics
Harvesting nonequilibrium hot carriers from plasmonic- metal nanostructures offers unique opportunities for driving photo- chemical reactions at the nanoscale. Despite numerous examples of hot electron-driven processes, the realization of plasmonic systems capable of harvesting hot holes from metal nanostructures has eluded the nascent field of plasmonic photocatalysis. In this work, we fabricate gold/p-type gallium nitride (Au/p-GaN) Schottky junctions tailored for photoelectrochemical studies of plasmon-induced hot-hole capture and conversion. Despite the presence of an interfacial Schottky barrier to hot-hole injection of more than 1 eV across the Au/p-GaN heterojunction, plasmonic Au/p-GaN photocathodes exhibit photoelectrochemical properties consistent with the injection of hot holes from Au nanoparticles into p- GaN upon plasmon excitation. The photocurrent action spectrum of the plasmonic photocathodes faithfully follows the surface plasmon resonance absorption spectrum of the Au nanoparticles and open-circuit voltage studies demonstrate a sustained photovoltage during plasmon excitation. Comparison with Ohmic Au/p-NiO heterojunctions confirms that the vast majority of hot holes generated via interband transitions in Au are sufficiently hot to inject above the 1.1 eV interfacial Schottky barrier at the Au/p-GaN heterojunction. We further investigated plasmon-driven photoelectrochemical CO2 reduction with the Au/p-GaN photocathodes and observed improved selectivity for CO production over H2 evolution in aqueous electrolytes. Taken together, our results offer experimental validation of photoexcited hot holes more than 1 eV below the Au Fermi level and demonstrate a photoelectrochemical platform for harvesting hot carriers to drive solar-to-fuel energy conversion.
- Research Organization:
- California Inst. of Technology (CalTech), Pasadena, CA (United States). Joint Center for Artificial Photosynthesis (JCAP)
- Sponsoring Organization:
- Swiss National Science Foundation (SNSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- SC0004993
- OSTI ID:
- 1469320
- Journal Information:
- Nano Letters, Journal Name: Nano Letters Journal Issue: 4 Vol. 18; ISSN 1530-6984
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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