Revealing the Relationship between Photocatalytic Properties and Structure Characteristics of TiO₂ Reduced by Hydrogen and Carbon Monoxide Treatment

Abstract

Reduction is considered to be an effective method to improve the photocatalytic activity of TiO ; however, the underlying relationship between structure and photocatalytic performance has not been adequately unveiled to date. To obtain insights into the effect of structure on photocatalytic activity, two types of reduced TiO were prepared from CO (CO-TiO ) and H (H-TiO ). For H-TiO , Ti-H bonds and oxygen vacancies are formed on the surface of H-TiO , which results in a more disordered surface lattice. However, for CO-TiO , more Ti-OH bonds are formed on the surface and more bulk oxygen vacancies are introduced; the disorder layer of CO-TiO is relatively thin, owing to most surface vacancies being filled by Ti-OH bonds. Under simulated solar irradiation, the photocatalytic H evolution rate of CO-TiO reaches 7.17 mmol g h , which is 4.14 and 1.50 times those of TiO and H-TiO , respectively. The photocatalytic degradation rate constant of methyl orange on CO-TiO is 2.45 and 6.39 times those on H-TiO and TiO . The superior photocatalytic activity of CO-TiO is attributed to the effective separation and transfer of photogenerated electron-hole pairs, due to the synergistic effects of oxygen vacancies and surface Ti-OH bonds. This study reveals the relationship between the photocatalytic properties and structure, and provides a new method to prepare highly active TiO for H production and environmental treatment.

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

“…However, in recent years deviations from this rule have been proposed to explain experimental observations. Thus, García-Melchor et al and Fernandez-Torre et al reported that H 2 dissociation on CeO 2 (111) follows a heterolytic path, with H being transferred from Ce to a neighboring O, generating the homolytic product [34,40]. Chen and Pacchioni reported that on nanostructured MgO (001), the dissociation pathway depends on the choice of the support—on MgO/Ag (001), the heterolytic pathway is preferred, while with Au support, it follows the homolytic dissociation [31].…”

Defect Engineering of Photocatalysts for Solar Energy Conversion

“…To introduce the defects into the semiconductors, chemical reduction approaches such as thermal treatment at reducing atmosphere, chemical reduction by reducing agents, and flame reduction are regarded as the promising strategies to create the surface defects into various photocatalysts. Using the reducing atmosphere, such as H 2 , CO, NH 3 , and H 2 S, various defects can be generated in the photocatalysts . For instance, CO and H 2 atmosphere were used to reduce TiO 2 , presenting the OVs and disorder layers in H–TiO 2 and CO–TiO 2 .…”

“…Using the reducing atmosphere, such as H 2 , CO, NH 3 , and H 2 S, various defects can be generated in the photocatalysts . For instance, CO and H 2 atmosphere were used to reduce TiO 2 , presenting the OVs and disorder layers in H–TiO 2 and CO–TiO 2 . Using thermal treatment, carbon vacancies confined in porous g‐C 3 N 4 nanosheets with sulfur‐doping were collected in NH 3 atmosphere .…”

Recent Progress on Defect‐rich Transition Metal Oxides and Their Energy‐Related Applications

“…Peng group prepared two types of TiO 2 in the reducing atmosphere of H 2 (H 2 À TiO 2 ) and CO (COÀ TiO 2 ). [64] H 2 À TiO 2 possesses TiÀ H bonds and oxygen vacancies on the surface, while TiÀ OH bonds and bulk oxygen vacancies will be found on the surface of COÀ TiO 2 ( Figure 5b). The relationship between photocatalytic performance and structure is revealed.…”

“…Gong group successfully prepared the sub‐stoichiometric single crystalline WO 3 nanosheets, then followed by post‐treatment using reducing gas and successfully introducing vacancies, [63] which exhibit significantly enhanced performance in photocatalytic water oxidation (Figure 5a). Peng group prepared two types of TiO 2 in the reducing atmosphere of H 2 (H 2 −TiO 2 ) and CO (CO−TiO 2 ) [64] . H 2 −TiO 2 possesses Ti−H bonds and oxygen vacancies on the surface, while Ti−OH bonds and bulk oxygen vacancies will be found on the surface of CO−TiO 2 (Figure 5b).…”