Preparation and photoelectrocatalytic activity of a nano-structured WO3 platelet film

A tungsten trioxide (WO{sub 3}) film was prepared by calcination from a precursor paste including suspended ammonium tungstate and polyethylene glycol (PEG). The ammonium tungstate suspension was yielded by an acid-base reaction of tungstic acid and an ammonium solution followed by deposition with ethanol addition. Thermogravimetric (TG) analysis showed that the TG profile of PEG is significantly influenced by deposited ammonium tungstate, suggesting that PEG is interacting strongly with deposited ammonium tungstate in the suspension paste. X-ray diffraction (XRD) data indicated that the WO{sub 3} film is crystallized by sintering over 400 deg. C. The scanning electron microscopic (SEM) measurement showed that the film is composed of the nano-structured WO{sub 3} platelets. The semiconductor properties of the film were examined by Mott-Schottky analysis to give flat band potential E{sub FB}=0.30 V vs. saturated calomel reference electrode (SCE) and donor carrier density N{sub D}=2.5x10{sup 22} cm{sup -3}, latter of which is higher than previous WO{sub 3} films by two orders of magnitude. The higher N{sub D} was explained by the large interfacial heterojunction area caused by the nano-platelet structure, which apparently increases capacitance per a unit electrode area. The WO{sub 3} film sintered at 550 deg. C produced 3.7 mA cm{supmore » -2} of a photoanodic current at 1.2 V vs. SCE under illumination with a 500 W xenon lamp due to catalytic water oxidation. This photocurrent was 4.5-12.8 times higher than those for the other control WO{sub 3} films prepared by similar but different procedures. The high catalytic activity could be explained by the nano-platelet structure. The photocurrent was generated on illumination of UV and visible light below 470 nm, and the maximum incident photon-to-current conversion efficiency (IPCE) was 47% at 320 nm at 1.2 V. Technically important procedures for preparation of nano-structured platelets were discussed. - Graphical abstract: A nano-structured WO{sub 3} platelet film was prepared by calcination from a precursor paste including suspended ammonium tungstate and polyethylene glycol. The ammonium tungstate suspension was yielded by an acid-base reaction of tungstic acid and an ammonium solution followed by deposition with ethanol addition. The photocatalytic activity of the film was 4.5-12.8 times higher than those for the other control WO{sub 3} films prepared by similar but different procedures.« less

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