title: Photocatalytic and photoelectrochemical water oxidation over metal-doped monoclinic BiVO(4) photoanodes.
abstract: The visible-light-induced water oxidation ability of metal-ion-doped BiVO(4) was investigated and of 12 metal ion dopants tested, only W and Mo dramatically enhanced the water photo-oxidation activity of bare BiVO(4); Mo had the highest improvement by a factor of about six. Thus, BiVO(4) and W- or Mo-doped (2 atom %) BiVO(4) photoanodes about 1 μm thick were fabricated onto transparent conducting substrate by a metal-organic decomposition/spin-coating method. Under simulated one sun (air mass 1.5G, 100 mW cm(-2)) and at 1.23 V versus a reversible hydrogen electrode, the highest photocurrent density (J(PH)) of about 2.38 mA cm(-2) was achieved for Mo doping followed by W doping (J(PH) ≈ 1.98 mA cm(-2)), whereas undoped BiVO(4) gave a J(PH) value of about 0.42 mA cm(-2). The photoelectrochemical water oxidation activity of W- and Mo-doped BiVO(4) photoanodes corresponded to the incident photon to current conversion efficiency of about 35 and 40 % respectively. Electrochemical impedance spectroscopy and Mott-Schottky analysis indicated a positive flat band shift of about 30 mV, a carrier concentration 1.6-2 times higher, and a charge-transfer resistance reduced by 3-4-fold for W- or Mo-doped BiVO(4) relative to undoped BiVO(4). Electronic structure calculations revealed that both W and Mo were shallow donors and Mo doping generated superior conductivity to W doping. The photo-oxidation activity of water on BiVO(4) photoanodes (undoped<W doped<Mo doped) was in accordance with the results from electrochemical impedance spectroscopy, Mott-Schottky analysis, and theoretical electronic structural calculations. Thus, Mo or W doping enhanced the photocatalytic and photoelectrochemical water oxidation activity of monoclinic BiVO(4) by drastically reducing its charge-transfer resistance and thereby minimizing photoexcited electron-hole pair recombination.
authors.affiliation: Department of Chemical Engineering and Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang, 790-784, South Korea.
authors.forename: Kanak Pal Singh
authors.initials: KP
authors.lastname: Parmar
authors.forename: Hyun Joon
authors.initials: HJ
authors.lastname: Kang
authors.forename: Amita
authors.initials: A
authors.lastname: Bist
authors.forename: Piyush
authors.initials: P
authors.lastname: Dua
authors.forename: Jum Suk
authors.initials: JS
authors.lastname: Jang
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Lee
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D002384:Catalysis; D004563:Electrochemistry; D004566:Electrodes; D008670:Metals / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011789:Quantum Theory; D014638:Vanadates / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D008670:Metals; D009930:Organic Chemicals; D014867:Water; C091754:bismuth vanadium tetraoxide; D014638:Vanadates; D001729:Bismuth