Insight into Charge Separation in WO3/BiVO4 Heterojunction for Solar Water Splitting.

Recently, the WO3/BiVO4 heterojunction has shown promising photoelectrochemical (PEC) water splitting activity based on its charge transfer and light absorption capability, and notable enhancement of the photocurrent has been achieved via morphological modification of WO3. We developed a graft copolymer-assisted protocol for the synthesis of WO3 mesoporous thin films on a transparent conducting electrode, wherein the particle size, particle shape, and thickness of the WO3 layer were controlled by tuning the interactions in the polymer/sol-gel hybrid. The PEC performance of the WO3 mesoporous photoanodes with various morphologies and the individual heterojunctions with BiVO4 (WO3/BiVO4) were characterized by measuring the photocurrents in the absence/presence of hole scavengers using light absorption spectroscopy and intensity-modulated photocurrent spectroscopy. The morphology of the WO3 photoanode directly influenced the charge separation efficiency within the WO3 layer and concomitant charge collection efficiency in the WO3/BiVO4 heterojunction, showing the smaller sized nanosphere WO3 layer showed higher values than did the plate-like or rod-like one. Notably, we observed that photocurrent density of WO3/BiVO4 was not dependent on the thickness of WO3 film or its charge collection time, implying slow charge flow from BiVO4 to WO3 can be a crucial issue in determining the photocurrent, rather than the charge separation within the nanosphere WO3 layer.

[1]  M. Kurihara,et al.  Dual-Functional Surfactant-Templated Strategy for Synthesis of an In Situ N2 -Intercalated Mesoporous WO3 Photoanode for Efficient Visible-Light-Driven Water Oxidation. , 2017, Chemistry.

[2]  Kyoung-Shin Choi,et al.  Nanoporous BiVO4 Photoanodes with Dual-Layer Oxygen Evolution Catalysts for Solar Water Splitting , 2014, Science.

[3]  Yun Jeong Hwang,et al.  Morphology control of one-dimensional heterojunctions for highly efficient photoanodes used for solar water splitting , 2014 .

[4]  Robert C. Tenent,et al.  The influence of sol-gel processing on the electrochromic properties of mesoporous WO3 films produced by ultrasonic spray deposition , 2014 .

[5]  Prashant V. Kamat,et al.  Dynamics of Photogenerated Charge Carriers in WO3/BiVO4 Heterojunction Photoanodes , 2015 .

[6]  Jae Sung Lee,et al.  Heterojunction BiVO4/WO3 electrodes for enhanced photoactivity of water oxidation , 2011 .

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

[8]  S. Ahn,et al.  Direct Assembly of Preformed Nanoparticles and Graft Copolymer for the Fabrication of Micrometer‐thick, Organized TiO2 Films: High Efficiency Solid‐state Dye‐sensitized Solar Cells , 2012, Advanced materials.

[9]  G. Gary Wang,et al.  Hydrogen-treated WO3 nanoflakes show enhanced photostability , 2012 .

[10]  Markus Niederberger,et al.  Nonaqueous sol-gel routes to metal oxide nanoparticles. , 2007, Accounts of chemical research.

[11]  Chang Soo Lee,et al.  High performance electrocatalyst consisting of CoS nanoparticles on an organized mesoporous SnO2 film: its use as a counter electrode for Pt-free, dye-sensitized solar cells. , 2015, Nanoscale.

[12]  Yiseul Park,et al.  Marked enhancement in electron-hole separation achieved in the low bias region using electrochemically prepared Mo-doped BiVO4 photoanodes. , 2014, Physical chemistry chemical physics : PCCP.

[13]  Takehiko Kitamori,et al.  Photocatalytic generation of hydrogen by core-shell WO3/BiVO4 nanorods with ultimate water splitting efficiency , 2015, Scientific Reports.

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

[15]  U. Steiner,et al.  Enhanced photocatalytic properties in well-ordered mesoporous WO3. , 2010, Chemical communications.

[16]  Yiseul Park,et al.  Progress in bismuth vanadate photoanodes for use in solar water oxidation. , 2013, Chemical Society reviews.

[17]  A. Yu,et al.  Effect of cation intercalation on the growth of hexagonal WO₃nanorods , 2012 .

[18]  G. Lanzani,et al.  Polymer-based photocathodes with a solution-processable cuprous iodide anode layer and a polyethyleneimine protective coating , 2016 .

[19]  G. Gao,et al.  Ordered mesoporous WO3 film with outstanding gasochromic properties , 2014 .

[20]  H. Bai,et al.  Large-Scale, Three–Dimensional, Free–Standing, and Mesoporous Metal Oxide Networks for High–Performance Photocatalysis , 2013, Scientific reports.

[21]  J. Robichaud,et al.  Controlled Growth of WO3Nanostructures with Three Different Morphologies and Their Structural, Optical, and Photodecomposition Studies , 2009, Nanoscale research letters.

[22]  C. Su,et al.  Photoelectrochemical application of mesoporous TiO2/WO3 nanohoneycomb prepared by sol–gel method , 2013 .

[23]  Can Li,et al.  Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4 , 2013, Nature Communications.

[24]  Weidong Yu,et al.  Electrochromic performance of WO3 films: optimization by crystal network topology modification , 2015 .

[25]  Y. Tachibana,et al.  Artificial photosynthesis for solar water-splitting , 2012, Nature Photonics.

[26]  J. T. Burke.  IR SPECTROSCOPY OR HOOKE'S LAW AT THE MOLECULAR LEVEL : A JOINT FRESHMAN PHYSICS-CHEMISTRY EXPERIENCE , 1997 .

[27]  S. Yin,et al.  Facile synthesis of homogeneous CsxWO3 nanorods with excellent low-emissivity and NIR shielding property by a water controlled-release process , 2011 .

[28]  T. Perng,et al.  Mesoporous TiO2/WO3 hollow fibers with interior interconnected nanotubes for photocatalytic application , 2014 .

[29]  Chang Soo Lee,et al.  Structural color-tunable mesoporous bragg stack layers based on graft copolymer self-assembly for high-efficiency solid-state dye-sensitized solar cells , 2016 .

[30]  Sang Ho Oh,et al.  Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures , 2014, Nature Communications.

[31]  Jing Wei,et al.  The fast and reversible intrinsic photochromic response of hydrated tungsten oxide nanosheets , 2015 .

[32]  J. S. Lee,et al.  Synthesis of hexagonal WO3 nanowires by microwave-assisted hydrothermal method and their electrocatalytic activities for hydrogen evolution reaction , 2010 .

[33]  A. Manthiram,et al.  Edge‐Oriented Tungsten Disulfide Catalyst Produced from Mesoporous WO3 for Highly Efficient Dye‐Sensitized Solar Cells , 2016 .

[34]  M. Whittingham,et al.  Structure of Hydrated Tungsten Peroxides [WO2(O2)H2O]·nH2O , 1998 .

[35]  Chang Soo Lee,et al.  Well-Organized Mesoporous TiO2 Photoanode by Using Amphiphilic Graft Copolymer for Efficient Perovskite Solar Cells , 2016 .

[36]  M. Whittingham,et al.  Structure of Hydrated Tungsten Peroxides [WO2(O2)H2O]×nH2O. , 1998 .