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Dual‐Functional Surfactant‐Templated Strategy for Synthesis of an In Situ N 2 ‐Intercalated Mesoporous WO 3 Photoanode for Efficient Visible‐Light‐Driven Water Oxidation
Author(s) -
Li Dong,
Chandra Debraj,
Takeuchi Ryouchi,
Togashi Takanari,
Kurihara Masato,
Saito Kenji,
Yui Tatsuto,
Yagi Masayuki
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201700088
Subject(s) - mesoporous material , materials science , tungsten trioxide , intercalation (chemistry) , visible spectrum , band gap , raman spectroscopy , nanotechnology , analytical chemistry (journal) , chemical engineering , inorganic chemistry , tungsten , chemistry , optoelectronics , catalysis , optics , biochemistry , chromatography , metallurgy , engineering , physics
N 2 ‐Intercalated crystalline mesoporous tungsten trioxide (WO 3 ) was synthesized by a thermal decomposition technique with dodecylamine (DDA) as a surfactant template with a dual role as an N‐atom source for N 2 intercalation, alongside its conventional structure‐directing role (by micelle formation) to induce a mesoporous structure. N 2 physisorption analysis showed that the specific surface area (57.3 m 2 g −1 ) of WO 3 templated with DDA (WO 3 ‐DDA) is 2.3 times higher than that of 24.5 m 2 g −1 for WO 3 prepared without DDA (WO 3 ‐bulk), due to the mesoporous structure of WO 3 ‐DDA. The Raman and X‐ray photoelectron spectra of WO 3 ‐DDA indicated intercalation of N 2 into the WO 3 lattice above 450 °C. The UV/Vis diffuse‐reflectance spectra exhibited a significant shift of the absorption edge by 28 nm, from 459 nm (2.70 eV) to 487 nm (2.54 eV), due to N 2 intercalation. This could be explained by the bandgap narrowing of WO 3 ‐DDA by formation of a new intermediate N 2p orbital between the conduction and valance bands of WO 3 . A WO 3 ‐DDA‐coated indium tin oxide (ITO) electrode calcined at 450 °C generated a photoanodic current under visible‐light irradiation below 490 nm due to photoelectrochemical water oxidation, as opposed to below 470 nm for ITO/WO 3 ‐bulk. The incident photon‐to‐current conversion efficiency (IPCE=24.5 %) at 420 nm and 0.5 V versus Ag/AgCl was higher than that of 2.5 % for ITO/WO 3 ‐bulk by one order of magnitude due to N 2 intercalation and the mesoporous structure of WO 3 ‐DDA.