Influence of Surface‐Related Phenomena on Mechanism, Selectivity, and Conversion of TiO₂‐Induced Photocatalytic Reactions

Abstract

Heterogeneous photocatalysis is the result of an inextricable connection of several factors differently contributing to the overall process. Photon absorption is the “sine qua non” condition for the reaction to occur. In fact, photons can be considered as immaterial reactants, and all of the phenomena related to the interaction of light–matter play a prominent role. However, other factors contribute in a concerted way to address the reaction, so that the relative contribution of each of them is often difficult to evaluate. In this framework, the present paper highlights some aspects of the interaction of TiO2 surface‐adsorbate species that could be underestimated and their influence on the conversion, selectivity, and mechanisms of photocatalytic reactions. To this aim, some paradigmatic examples on the adsorption of water and organics on TiO2 are reported.

Insights into the TiO2-Based Photocatalytic Systems and Their Mechanisms

“…Considering the PC process in TiO 2 , the VB and CB level of TiO 2 lies at +2.9 and −0.3 eV, respectively, which leads to the band gap energy of 3.2 eV. It should be noted that the VB and CB level of TiO 2 lies at more positive and more negative values in comparison with the standard redox potential of O 2 /H 2 O (1.23 eV) and H+/H 2 (0 eV) vs. normal hydrogen electrode (NHE), which is one of the more favorable conditions for the photocatalytic redox reactions [31,32].…”

Light-Induced Advanced Oxidation Processes as PFAS Remediation Methods: A Review

“…[97], copyright (2020) with permission from ACS publications) and (b) the z-scheme based heterojunction of core-shell CeO2@NiAl-LDHs (reprinted from [99], copyright (2021) with permission from Elsevier). The reaction has been investigated in irradiated aqueous suspensions of TiO 2 , one of the most extensively investigated photocatalysts, and the commonly accepted mechanism is the result of a photo-redox and β-scission pathway [104] Upon irradiation of suitable energy, electrons (e − CB ) and holes (h + VB ) are localized respectively within the conduction and valence band of TiO 2 [105], according to Equation (2).…”

Enhanced Solar Light Photocatalytic Activity of Ag Doped TiO2–Ag3PO4 Composites

“…Yao et al [26] reported the enhanced visible light photocatalytic activity of Ag 3 PO 4 nanoparticles deposited onto commercial TiO 2 (Evonik P25). In this case, degradation of dyes such as methylene blue and rhodamine B have been used as model visible light reactions, so that it is difficult to assess if a direct or indirect photocatalytic process is taking place [27]. However, results were confirmed by Rawal et al [28], which used a homemade polycrystalline TiO 2 coupled with Ag 3 PO 4 for the visible light degradation of 2-propanol in gas phase.…”