Oxygen vacancy self-doped single crystal-like TiO ₂ nanotube arrays for efficient light-driven methane non-oxidative coupling

Abstract

Photocatalytic non-oxidative coupling of methane (PNOCM) is a mild and cost-effective method for the production of multicarbon compounds. However, the separation of photogenerated charges and activation of methane (CH 4 ) are the main challenges for this reaction. Here, single crystal-like TiO 2 nanotubes (V O -p-TNTs) with oxygen vacancies (V O ) and preferential orientation were prepared and applied to PNOCM. The results demonstrate that the significantly enhanced photocatalytic performance is mainly related to the strong synergistic effect between preferential orientation and V O . The preferential orientation of V O -p-TNT along the [001] direction reduces the formation of complex centers at grain boundaries as the form of interfacial states and potential barriers, which improves the separation and transport of photogenerated carriers. Meanwhile, V O provides abundant coordination unsaturated sites for CH 4 chemisorption and also acts as electron traps to hinder the recombination of electrons and holes, establishing an effective electron transfer channel between the adsorbed CH 4 molecule and photocatalyst, thus weakening the C-H bond. In addition, the introduction of V O broadens the light absorption range. As a result, V O -p-TNT exhibits excellent PNOCM performance and provides new insights into catalyst design for CH 4 conversion.

Photocatalytic non-oxidative conversion of methane

“…Furthermore, the Shen Qianqian group designed single-crystal-like TiO 2 nanotubes (V O -p-TNTs) to improve the separation and transport of photogenerated carriers, thereby enhancing the methane conversion efficiency. 44…”

Effective charge separation in photoelectrochemical water splitting: a review from advanced evaluation methods to materials design

“…Defects can be observed and verified through different experimental methods. 71–74 Fang et al used a chemical vapor deposition technique to engineer Mo-doped BiVO 4 (Mo:BVO). The crystal orientation reconstruction in the samples could be detected by cross-section high-resolution transmission electron microscopy (HRTEM), as shown in Fig.…”

Cooperation of Strong Electric Field and H2O Dissociation on Co3O4-Decorated SiC Rods for Photodriven CO2 Methanation with 100% Selectivity

“…To promote photocatalytic CO 2 methanation, many strategies have been applied to improve the photoexcited charge separation, CO 2 absorption and activation, formation of necessary intermediates, and desorption of methane. Strong metal support interactions, defect vacancies, − ultrathin 2D nanosheets, porous materials, supramolecular modification, alloys, single (double)-atom, crystal facet, and metal or nonmetallic impurities were painstakingly designed on photocatalysts as electron sinks or CO 2 absorption sites for the product selectivity. For comparison, the construction of a heterojunction is one of the most direct and effective ways to produce highly selective CH 4 , which could simply integrate the reducing semiconductor and the oxidizing semiconductor into one photocatalyst.…”