title: A silicon-based photocathode for water reduction with an epitaxial SrTiO3 protection layer and a nanostructured catalyst.
abstract: The rapidly increasing global demand for energy combined with the environmental impact of fossil fuels has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. Here we show that a silicon-based photocathode with a capping epitaxial oxide layer can provide efficient and stable hydrogen production from water. In particular, a thin epitaxial layer of strontium titanate (SrTiO3) was grown directly on Si(001) by molecular beam epitaxy. Photogenerated electrons can be transported easily through this layer because of the conduction-band alignment and lattice match between single-crystalline SrTiO3 and silicon. The approach was used to create a metal-insulator-semiconductor photocathode that, under a broad-spectrum illumination at 100 mW cm(-2), exhibits a maximum photocurrent density of 35 mA cm(-2) and an open circuit potential of 450 mV; there was no observable decrease in performance after 35 hours of operation in 0.5 M H2SO4. The performance of the photocathode was also found to be highly dependent on the size and spacing of the structured metal catalyst. Therefore, mesh-like Ti/Pt nanostructured catalysts were created using a nanosphere lithography lift-off process and an applied-bias photon-to-current efficiency of 4.9% was achieved.
authors.affiliation: 1] Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA [2] Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Ji
authors.affiliation: Department of Chemical Engineering, University of Texas at Austin, Texas 78712, USA.
authors.forename: Martin D
authors.initials: MD
authors.lastname: McDaniel
authors.affiliation: Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712, USA.
authors.forename: Shijun
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Physics, University of Texas at Austin, Texas 78712, USA.
authors.forename: Agham B
authors.initials: AB
authors.lastname: Posadas
authors.affiliation: Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA.
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Li
authors.affiliation: Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA.
authors.forename: Haiyu
authors.initials: H
authors.lastname: Huang
authors.affiliation: Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA.
authors.forename: Jack C
authors.initials: JC
authors.lastname: Lee
authors.affiliation: Department of Physics, University of Texas at Austin, Texas 78712, USA.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Demkov
authors.affiliation: Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Texas 78712, USA.
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Bard
authors.affiliation: Department of Chemical Engineering, University of Texas at Austin, Texas 78712, USA.
authors.forename: John G
authors.initials: JG
authors.lastname: Ekerdt
authors.affiliation: Microelectronics Research Center, Department of Electrical and Computer Engineering, University of Texas at Austin, Texas 78712, USA.
authors.forename: Edward T
authors.initials: ET
authors.lastname: Yu