Molecular Transport Through TiO2 Mesoporous Thin Films: Correlation with the Partially Blocked Electrodes model

PAULA Y. STEINBERG; FRANCO ZANOTTO; GALO J. A. A. SOLER-ILLIA; SERGIO A. DASSIE; PAULA C. ANGELOMÉ

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2021 vol. 125 p. 23521 - 23532

1932-7447

Mesoporous titania thin films (MTTFs) based electrodes are vastly popular due to their versatilityand their potential use as sensors, catalysts, and photovoltaic devices. For these applications,understanding of diffusion through the pores along the thickness of the films is critical. Cyclicvoltammetry with the use of a freely diffusing redox probe is a promising and simple strategy forthe characterization of this kind of modified electrodes. However, the application of a mesoporousinsulating material on a flat electrode greatly modifies the diffusion regimes in the vicinity of thereaction zone. This makes the use of traditional tools for data interpretation, such as the RandlesB-C(> equation, insufficient. In this work, the application of a model previously developed forpartially covered electrodes (Matsuda et al., J. Electroanal. Chem. 1979, 101 (1), 29-38) isproposed to interpret experimental results. An excellent agreement between experimental andsimulated voltammograms was achieved for MTTFs with different pore sizes and pore arrays. Thisanalysis can be attributed to a lack of uniformity along the films related to differences in pore-topore connectivity along the thickness of the film. At the same time, it is revealed that pore andneck sizes are determinant for diffusion within these materials. Thus two dimensions govern theelectrochemical results: nano-pores size and array, and micro-regions with different connectivityalong the MTTF.