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Published April 11, 2018 | Supplemental Material
Journal Article Open

Hot Hole Collection and Photoelectrochemical CO_2 Reduction with Plasmonic Au/p-GaN Photocathodes


Harvesting nonequilibrium hot carriers from plasmonic-metal nanostructures offers unique opportunities for driving photochemical 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. Here, 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 CO_2 reduction with the Au/p-GaN photocathodes and observed improved selectivity for CO production over H_2 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.

Additional Information

© 2018 American Chemical Society. Received: January 18, 2018; Revised: February 28, 2018; Publication Date (Web): March 9, 2018. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC0004993. G.T. acknowledges support from the Swiss National Science Foundation through the Early Postdoc Mobility Fellowship, Grant P2EZP2_159101 and the Advanced Mobility Fellowship, Grant P300P2_171417. We thank Dr. Ravishankar Sundararaman, Dr. Prineha Narang, and Adam Jermyn for fruitful discussions of hot-carrier energy distributions. We thank Dr. Matthias Richter for XPS characterization of p-type NiO films. Author Contributions: J.S.D., G.T., and H.A.A. conceived the idea, designed the experiments, and wrote the manuscript. J.S.D. and G.T. performed all photoelectrochemical experiments. J.S.D., G.T., and A.J.W. fabricated devices. W.-H.C. performed optical characterization and assisted with gas chromatography experiments. H.A.A. supervised the project. All authors have given approval to the final version of the manuscript. The authors declare no competing financial interest.

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August 19, 2023
October 18, 2023