The role of TiO2:SnO2 heterojunction for partial oxidation of methane by photoelectrocatalytic process at room temperature

• Published in: Journal of alloys and compounds Vol. 968; p. 172090
• Main Authors: e Silva, Ricardo Marques, de Lourdes Souza, Fernanda, Dias, Eduardo, da Silva, Gelson Tiago dos Santos Tavares, Durán, Florymar Escalona, Rego, Arjun, Higgins, Drew, Ribeiro, Caue
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-12-2023
• Subjects: CH4 oxidation; Methane oxidation; Photoelectrocatalysis; TiO2:SnO2 heterojunction; Photoelectrocatalysis; TiO2:SnO2 heterojunction; Methane oxidation; CH4 oxidation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.172090

Partial Oxidation of Methane into hydrocarbons using photoelectrochemical routes is attractive from a sustainability point of view owing to the possibility of using renewable energy (i.e., solar illumination) to activate this stable molecule. However, the process demands the development of novel catalysts that can promote methane activation and oxidation in a controlled manner to increase energy conversion efficiency. Herein, we demonstrated that semiconductor heterostructures improved charge separation compared to the individual materials alone. A more effortless transfer between bands favors the separation of the electron-hole (e−/h+) pairs generated by the photoelectrocatalytic system and prevents them from recombining. This process produces reactive oxygens, essential to driving methane oxidation conversion of the C–H bond cleavage. TiO2:SnO2 semiconductor heterojunction catalysts in film shape were investigated for methane oxidation via a photoelectrocatalytic process. The methane oxidation reactions were carried out in an inflow and sealed electrochemical system for 1 h. Liquid-state nuclear magnetic resonance revealed methanol and acetic acid as the main liquid products, where the TiO2:SnO2 heterojunction exhibited better performance with values of 30 and 8 µmol.cm−2.h−1, respectively. Compared to their materials alone, the superior performance of the TiO2:SnO2 heterojunction is attributed to the formation of heterostructure type II that enables a more effortless transfer between bands, facilitating the separation of the generated e−/h+ pairs under UV-Vis irradiation. The outcomes achieved here will motivate further studies for developing semiconductor heterojunction structure catalysts in photoelectrocatalysis to partially oxidize methane into valuable chemicals.
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•We synthesized and characterized TiO2:SnO2 heterojunction as a model catalyst for controlled photoelectrochemical methane oxidation.•As-synthesized TiO2:SnO2 heterojunction catalysts and their individual materials alone (i.e., TiO2-anatase and SnO2-rutile) in film-shaped were investigated for methane oxidation via photoelectrocatalytic process under mild conditions.•TiO2:SnO2 heterostructure excited by photoelectron source exhibited superior performance for methanol and acetic acid production when compared to their individual materials alone and excited by different sources (i.e., photon and electron).•The superior production could be attributed to the heterojunction mechanism between TiO2-anatase and SnO2-rutile materials that enables a more effortless transfer between bands, facilitating the separation of the generated electron-hole (e−/h+), liable for producing reactive oxygens ; essential to driving methane oxidation conversion by the C–H bond cleavage.