Hydrogen-treated WO3 nanoflakes show enhanced photostability

Here we report that photostability and photoactivity of WO3 for water oxidation can be simultaneously enhanced by controlled introduction of oxygen vacancies into WO3 in hydrogen atmosphere at elevated temperatures. In comparison to pristine WO3, the hydrogen-treated WO3 nanoflakes show an order of magnitude enhanced photocurrent, and more importantly, exhibit extraordinary stability for water oxidation without loss of photoactivity for at least seven hours. The enhanced photostability is attributed to the formation of substoichiometric WO3−x after hydrogen treatment, which is highly resistive to the re-oxidation and peroxo-species induced dissolution. This work constitutes the first example where WO3 can be stabilized for water oxidation in neutral medium without the need for oxygen evolution catalysts. The demonstration of electrochemically stable WO3 could open up new opportunities for WO3 based photoelectrochemical and photocatalytic applications.

[1]  Jennifer K. Hensel,et al.  Synergistic effect of CdSe quantum dot sensitization and nitrogen doping of TiO(2) nanostructures for photoelectrochemical solar hydrogen generation. , 2010, Nano letters.

[2]  Nathan S. Lewis,et al.  Evaluation of Pt, Ni, and Ni–Mo electrocatalysts for hydrogen evolution on crystalline Si electrodes , 2011 .

[3]  Fang Qian,et al.  Double-sided CdS and CdSe quantum dot co-sensitized ZnO nanowire arrays for photoelectrochemical hydrogen generation. , 2010, Nano letters.

[4]  Yichuan Ling,et al.  Hydrogen-treated TiO2 nanowire arrays for photoelectrochemical water splitting. , 2011, Nano letters.

[5]  M. Schiavello,et al.  X-ray photoelectron spectroscopy study of nonstoichiometric tungsten oxides , 1977 .

[6]  Daniel R. Gamelin,et al.  Composite photoanodes for photoelectrochemical solar water splitting , 2010 .

[7]  J. A. Seabold,et al.  Effect of a Cobalt-Based Oxygen Evolution Catalyst on the Stability and the Selectivity of Photo-Oxidation Reactions of a WO3 Photoanode , 2011 .

[8]  R. Colton,et al.  Photochromism and electrochromism in amorphous transition metal oxide films , 1978 .

[9]  Daniel G. Nocera,et al.  In Situ Formation of an Oxygen-Evolving Catalyst in Neutral Water Containing Phosphate and Co2+ , 2008, Science.

[10]  Michael Grätzel,et al.  New Benchmark for Water Photooxidation by Nanostructured α-Fe2O3 Films , 2006 .

[11]  S. Alamri.  Study of thermocolored WO3 thin film under direct solar radiation , 2009 .

[12]  Jinmin Wang,et al.  Controlled synthesis of WO3 nanorods and their electrochromic properties in H2SO4 electrolyte , 2009 .

[13]  Liejin Guo,et al.  Vertically aligned WO₃ nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis and photoelectrochemical properties. , 2011, Nano letters.

[14]  Ryuhei Nakamura,et al.  Primary intermediates of oxygen photoevolution reaction on TiO2 (Rutile) particles, revealed by in situ FTIR absorption and photoluminescence measurements. , 2004, Journal of the American Chemical Society.

[15]  Xiaobo Chen,et al.  Increasing Solar Absorption for Photocatalysis with Black Hydrogenated Titanium Dioxide Nanocrystals , 2011, Science.

[16]  F. G. Wakim.  Some effects of trapping on the photoelectronic properties of TiO2 single crystals , 1970 .

[17]  I. Parkin,et al.  Photocatalytically active gamma-WO3 films from the atmospheric pressure CVD of WOCl4 with ethyl acetate or ethanol , 2004 .

[18]  Robert J. Lad,et al.  Stoichiometry and microstructure effects on tungsten oxide chemiresistive films , 2001 .

[19]  Y. Yun,et al.  Spectroscopic analysis of tungsten oxide thin films , 2010 .

[20]  Jianjun He,et al.  Photoelectrochemistry of Nanostructured WO3 Thin Film Electrodes for Water Oxidation: Mechanism of Electron Transport , 2000 .

[21]  P. Schmuki,et al.  A Photo-Electrochemical Investigation of Self-Organized TiO2 Nanotubes , 2010 .

[22]  Fan Zhang,et al.  Water splitting by tungsten oxide prepared by atomic layer deposition and decorated with an oxygen-evolving catalyst. , 2011, Angewandte Chemie.

[23]  M. Sunkara,et al.  WO3 and W2N nanowire arrays for photoelectrochemical hydrogen production , 2009 .

[24]  J. Augustynski,et al.  Crystallographically oriented mesoporous WO3 films: synthesis, characterization, and applications. , 2001, Journal of the American Chemical Society.

[25]  D. Cahen,et al.  Tungsten trioxide as a photoanode for a photoelectrochemical cell (PEC) , 1976, Nature.

[26]  Fang Qian,et al.  Nitrogen-doped ZnO nanowire arrays for photoelectrochemical water splitting. , 2009, Nano letters.

[27]  P. Patil,et al.  Titanium doping effects in electrochromic pulsed spray pyrolysed WO3 thin films , 2008 .

[28]  Liejin Guo,et al.  Nanostructured WO₃/BiVO₄ heterojunction films for efficient photoelectrochemical water splitting. , 2011, Nano letters.

[29]  M. Anik,et al.  Dissolution kinetics of WO3 in acidic solutions , 2006 .

[30]  Y. Zhao,et al.  LASER-INDUCED COLORATION OF WO3 , 1997 .

[31]  D. Butt,et al.  The Nature of Oxide Films on Tungsten in Acidic and Alkaline Solutions , 1998 .

[32]  S. Seal,et al.  Studies on passivation behavior of tungsten in application to chemical mechanical polishing , 1999, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films.

[33]  S. Cho,et al.  Synthesis of transparent mesoporous tungsten trioxide films with enhanced photoelectrochemical response: application to unassisted solar water splitting† , 2011 .

[34]  B. Bartlett,et al.  Electrochemical deposition and photoelectrochemistry of CuWO4, a promising photoanode for water oxidation , 2011 .

[35]  Zhengjun Zhang,et al.  LETTER TO THE EDITOR: Low-temperature synthesis of large-scale arrays of aligned tungsten oxide nanorods , 2003 .

[36]  F. Cardon,et al.  On the determination of the flat-band potential of a semiconductor in contact with a metal or an electrolyte from the Mott-Schottky plot , 1978 .

[37]  G. Brudvig,et al.  A functional model for O-O bond formation by the O2-evolving complex in photosystem II. , 1999, Science.

[38]  Qi-yuan Chen,et al.  Photoelectrochemical and physical properties of WO3 films obtained by the polymeric precursor method , 2010 .

[39]  S. K. Deb.  Electron spin resonance of defects in single crystal and thin films of tungsten trioxide , 1977 .

[40]  A. Fujishima,et al.  Electrochemical Photolysis of Water at a Semiconductor Electrode , 1972, Nature.

[41]  Yichuan Ling,et al.  Sn-doped hematite nanostructures for photoelectrochemical water splitting. , 2011, Nano letters.

[42]  J. Augustynski,et al.  Silver nanoparticle induced photocurrent enhancement at WO3 photoanodes. , 2010, Angewandte Chemie.

[43]  M. Pelino,et al.  Microstructural effect on NO2 sensitivity of WO3 thin film gas sensors Part 1. Thin film devices, sensors and actuators , 1996 .

[44]  C. Grimes,et al.  Vertically aligned single crystal TiO2 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis details and applications. , 2008, Nano letters.

[45]  Yichuan Ling,et al.  Facile synthesis of highly photoactive α-Fe₂O₃-based films for water oxidation. , 2011, Nano letters.