Uncovering Electrochemical Methane Oxidation Mechanism through the In Situ Detection of Reaction Intermediates
The electrochemical partial oxidation of methane (CH4) to value-added chemicals under ambient conditions provides a solution for harnessing abundant natural gas resources. Here, we investigate α-Fe2O3 as a model catalyst to gain a mechanistic understanding of the electrochemical CH4 oxidation reacti...
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Veröffentlicht in: | ACS catalysis 2024-07, Vol.14 (14), p.10614-10623 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The electrochemical partial oxidation of methane (CH4) to value-added chemicals under ambient conditions provides a solution for harnessing abundant natural gas resources. Here, we investigate α-Fe2O3 as a model catalyst to gain a mechanistic understanding of the electrochemical CH4 oxidation reaction (eCH4OR). During chronoamperometric experiments, we obtain liquid products (formic acid, acetic acid, and acetone) with ∼6.5% total Faradaic efficiency at 2.3 V versus the reversible hydrogen electrode (VRHE). At lower potentials below 2.0 VRHE, non-Faradaic CH4 adsorption occurred, confirmed by in situ ATR-SEIRAS (attenuated total reflectance–surface-enhanced infrared absorption spectroscopy) and impedance spectroscopies. In addition to verifying the presence of the FeIVO species, in situ spectroelectrochemical measurements revealed that CH4 oxidation initiates via H-abstraction to form •OCH3 species. The reaction undergoes further oxidation steps, leading to formate. Coupling between •OCH3 and formate generates •OCOCH3 species. Further, C–C coupling between – COCH3 and – CH3 resulted in acetone formation. Real-time proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) confirms the proposed pathways. Based on these observations, we propose a mechanistic pathway for selective CH4 electrooxidation. |
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ISSN: | 2155-5435 2155-5435 |
DOI: | 10.1021/acscatal.4c00675 |