Ultrathin PdAu Nanowires with High Alloying Degree for the Direct Oxidation of Methane to C1 Oxygenates

Abstract

The direct oxidation of methane (CH ₄) into high-valued C1 oxygenates production has garnered increased attention in effectively using vast CH ₄ and alleviating the global energy crisis. However, due to the high cleavage energy of C—H bond and low polarity of CH ₄ molecule, it is difficult to activate the first C—H bond. Furthermore, C1 oxygenates are readily inclined to be oxidized to CO ₂, because their weaker C—H bond comparing with CH ₄ molecule, resulting in poor selectivity. Herein, we designed ultrathin Pd xAu y alloy NWs supported on ZSM-5 (Z-5) to investigate the direct oxidation of CH ₄ to high value-added oxygenate under mild conditions. By precisely adjusting the molar ratio of Pd/Au and alloying degree, Pd ₉Au ₁NWs/Z-5 showed an excellent yield of 11.57 mmol·g ^-l·h ^-1 and the outstanding selectivity of 95.1% for C1 oxygenates (CH ₃OH, CH ₃OOH and HCOOH). The  in-situ spectroscopic and mechanism analysis proved that the enhanced catalytic performance of Pd ₉Au ₁NWs/Z-5 was ascribed to the stable one-dimensional nanostructure and the strong synergy effect with high alloying PdAu, which could increase the adsorption capacity of CH ₄ molecules on Pd atoms to promote the CH ₄ conversion. This work offers valuable insights into the design concept of high-efficient catalysts and the structure-activity relationship for the direct oxidation of CH ₄.

Keywords

Heterogeneous catalysis / Synergetic Effect / Supported catalysts / Direct oxidation of CH ₄ / PdAu alloy / Nanowires / C1 oxygenates / In-situ DRIFTS

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2024 SIOC, CAS, Shanghai, & WILEY-VCH GmbH