Photoelectrochemical Behavior of Nanostructured WO₃ Thin‐Film Electrodes: The Oxidation of Formic Acid

Abstract

Nanostructured tungsten trioxide thin-film electrodes are prepared on conducting glass substrates by either potentiostatic electrodeposition from aqueous solutions of peroxotungstic acid or direct deposition of WO3 slurries. Once treated thermally in air at 450 degrees C, the electrodes are found to be composed of monoclinic WO3 grains with a particle size around 30-40 nm. The photoelectrochemical behavior of these electrodes in 1 M HClO4 apparently reveals a low degree of electron-hole recombination. Upon addition of formic acid, the electrode showed the current multiplication phenomenon together with a shift of the photocurrent onset potential toward less positive values. Photoelectrochemical experiments devised on the basis of a kinetic model reported recently [I. Mora-Seró, T. Lana-Villarreal, J. Bisquert, A. Pitarch, R. Gómez, P. Salvador, J. Phys. Chem. B 2005, 109, 3371] showed that an interfacial mechanism of inelastic, direct hole transfer takes place in the photooxidation of formic acid. This behavior is attributed to the tendency of formic acid molecules to be specifically adsorbed on the WO3 nanoparticles, as evidenced by attenuated total reflection infrared spectroscopy.

A visible-light-induced photoelectrochemical water-splitting system featuring an organo-photocathode along with a tungsten oxide photoanode

“…2.7 eV) corresponding to the absorption edge of ca. 460 nm 18,21,23,42,43 ]. As for the ITO/ZnPc/ C 60 -Pt photocathode capable of H 2 evolution, its action spectrum has previously been claried to originate in the entire visible-light absorption of both ZnPc and C 60 .…”

Graphitic g-C3N4-WO3Composite: Synthesis and Photocatalytic Properties

“…2.7 eV can be capable of harvesting the blue part of the solar spectrum, 5 and is photostable in acid media, which makes it useful in photocatalysis for wastewater treatment in the presence of organic acids. 6 Therefore, tungsten oxide WO 3 is of particular interest in photocatalysts in the past decades. 7 However, it has some drawbacks in practical application because of its high solubility in water 6 and poor photodegradation of organic compounds under O 2 condition due to its conduction band edge with a position unfavorable for single-electron reduction of O 2 .…”

“…6 Therefore, tungsten oxide WO 3 is of particular interest in photocatalysts in the past decades. 7 However, it has some drawbacks in practical application because of its high solubility in water 6 and poor photodegradation of organic compounds under O 2 condition due to its conduction band edge with a position unfavorable for single-electron reduction of O 2 .…”

Photo‐electrochemical Oxidation of Organic C1 Molecules over WO3 Films in Aqueous Electrolyte: Competition Between Water Oxidation and C1 Oxidation

“…For measurements in pure supporting electrolyte (0.5 m H 2 SO 4 ), the photocurrent sets in at approximately 0.6 V, in good agreement with previous studies on the photo-electrochemistry of WO 3 . [8,18,19] In solutions containing C1 molecules, the photocurrents ( Figure 4a) show lower onset potentials (see inset of Figure 4a)a sw ell as higher maximum photocurrents, where the exact values depend on the organic molecule present in the electrolyte. For the oxidation of formic acid, the photocurrent onset is shifted to al ower value of about 0.5V ,i ng ood agreement with literature reports.…”

“…For the oxidation of formic acid, the photocurrent onset is shifted to al ower value of about 0.5V ,i ng ood agreement with literature reports. [19] The higher photocurrentd uring the photo-electrochemical oxidation of small organic molecules compared to that obtained in pure supporting electrolyte is generally explained by the so-called "current doubling"m echanism introduced by Morrisona nd Freund. [28] After generation of an electron-hole pair [Eq.…”