Electron Transfer at the  WO 3 ‐ Electrolyte Interface under Controlled Mass Transfer Conditions

Abstract

The reduction of Fe3+ and Ce4+ at a polycrystalline n‐WO3 rotating disk electrode was studied in the dark as a function of potential, concentration of oxidized species, and rotation frequency. The measured current densities are shown to fit reasonably well to a model which involves electron transfer from the bulk of the semiconductor to the surface (rate constant K1 ) and from the surface to the solution false(K2false) and which involves transport of the oxidized species to the electrode surface false(K3false) . The dependence of K1 and K2 on electrode potential reveals that a significant portion of the potential drop occurs over the Helmholtz layer, indicating partial Fermi level pinning.

Tungsten trioxide and titanium dioxide photocatalytic degradations of quinoline

“…This conclusion is based upon measurement of photocurrent in the presence and absence of methanol. Although the catalyst is not identical to the present case, the authors discuss the generality of this mechanism 13 . The chemical contrast, in that case, is that hydrogen abstraction of the C-H is the first step of methanol oxidation, rather than SET, followed by deprotonation, current doubling, and so on.…”

“…Upon irradiation with high intensity sound or ultrasound irradiation, a process called acoustic cavitation occurs 13 . Gas bubbles are formed in solution, which rapidly implode creating small, localized intense conditions in otherwise cold solutions with temperatures of nearly 5000K and pressures of 1000 atm.…”

“…13) and the CB electron can react directly with an acceptor (A) organic molecule (equation 1.14). The final equation in this scheme describes the recombination of the conduction band electron and valence band hole to generate heat.…”

“…14 Most current research supports an alternative proposal in which the dopant atom orbitals generate an isolated mid-gap level above the valence band. 13,27,33,[53][54][55][56] Intuitively, this point is a key one for understanding the chemistry that these catalysts will initiate, given that oxidation is the main TiO 2 -mediated degradation pathway. Raising the bulk valence band energy level would necessarily lower the oxidizing power of the photochemically generated hole and potentially interfere with certain reactions the pristine catalyst could perform.…”

“…13,47,55,57 Others have recently noted wavelength-dependent chemistry for N-TiO 2 remediation of ethylene glycol in acetonitrile, 55 as well as C-TiO 2 -mediated degradation of molecules with different binding abilities and oxidation potentials. 13 To probe the photocatalytic activity of doped titania, many other studies have used dyes as chemical probes, some of which are prone to both oxidative and reductive degradation pathways and are often unrepresentatively easy to oxidize or reduce, compared to more common relevant pollutants. Dyes also absorb light is the visible region, which is an undesirable trait.…”