Rate?limiting step in environmental Bi2WO6/solar light photoelectrocatalysis

CABRERIZO, FRANCO M.; VARGAS, RONALD; MADRIZ, LOREAN; CARVAJAL, DAVID; NÚÑEZ, OSWALDO; DÍAZ, ABNEL

Cartagena

Otro; Caribbean School on Materials for Clean Energy " Organizado por Abdus Salam International Centre for Theoretical Physics (ICTP); 2019

Bi2WO6 /solar light photocatalysis was used to probe the rate- limiting step (rls) on this Aurivillius oxide. An unusually large solventisotope effect has been measured during glucose oxidation (kH2O/kD2Oaround 7). The large value come from the contribution of the equilibrium L2O⇄ L+ + OL− previous to the rls and the kineticone proton transfer involved at the transition state. The rls is the 1e−Volmer type electrosorption of H+ on the Bi2WO6surface (Bi2WO6/Bi2WO6‐H, −0.6 V vs. NHE). Subsequently, O2reduction to L2O, as driving force, occurs at the catalystconduction band (CB). Kinetic constant measurements as a function of thesolution pH, photoluminescence spectroscopy in presence of different electronacceptor (O2, H2O2 and S2O82-)and electrochemical experiments at diverse type of irradiation (dark, sunlight:UV-Vis and Vis), support these results. In fact, positive conduction bandpotential of Bi2WO6 (+0.5 V vs. NHE) establishes the difference with other semiconductors whereoxidation (L2O/L+, OL?) instead of reduction has been proposed as rls in photo - oxidation.Strategies to enhance environmental photocatalysis by matching the redoxassistance at the semiconductor CB with the appropriate photon flux have been envisaged.