title: Photocatalytic generation of hydrogen by core-shell WO₃/BiVO₄ nanorods with ultimate water splitting efficiency.
abstract: Efficient photocatalytic water splitting requires effective generation, separation and transfer of photo-induced charge carriers that can hardly be achieved simultaneously in a single material. Here we show that the effectiveness of each process can be separately maximized in a nanostructured heterojunction with extremely thin absorber layer. We demonstrate this concept on WO3/BiVO4+CoPi core-shell nanostructured photoanode that achieves near theoretical water splitting efficiency. BiVO4 is characterized by a high recombination rate of photogenerated carriers that have much shorter diffusion length than the thickness required for sufficient light absorption. This issue can be resolved by the combination of BiVO4 with more conductive WO3 nanorods in a form of core-shell heterojunction, where the BiVO4 absorber layer is thinner than the carrier diffusion length while it's optical thickness is reestablished by light trapping in high aspect ratio nanostructures. Our photoanode demonstrates ultimate water splitting photocurrent of 6.72 mA cm(-2) under 1 sun illumination at 1.23 V(RHE) that corresponds to ~90% of the theoretically possible value for BiVO4. We also demonstrate a self-biased operation of the photoanode in tandem with a double-junction GaAs/InGaAsP photovoltaic cell with stable water splitting photocurrent of 6.56 mA cm(-2) that corresponds to the solar to hydrogen generation efficiency of 8.1%.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Pihosh
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2-13, Tsukuba, Ibaraki 305-0047, Japan.|National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Ivan
authors.initials: I
authors.lastname: Turkevych
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Mawatari
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Uemura
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kazoe
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.|Chernivtsy National University, Institute of Physics, Engineering and Computer Science, Storozhynetska 101, Chernivtsy, 58000 Ukraine.
authors.forename: Sonya
authors.initials: S
authors.lastname: Kosar
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2-13, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Kikuo
authors.initials: K
authors.lastname: Makita
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2-13, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Sugaya
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2-13, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsui
authors.affiliation: National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Fujita
authors.affiliation: National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tosa
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2-13, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Kondo
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Kitamori