【Frontiers in HaiChuan Chemical Technology】The Dahuaxing Research Institute, in collaboration with Fudan University, has proposed a new approach for the efficient and synergistic conversion of methane through high-temperature electrocatalysis

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Recently, Song Yuefeng, an associate researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, together with the team led by Professor Wang Guoxiong from Fudan University, made new progress in the research on high-temperature electrocatalytic conversion using solid oxide electrolyte cells (SOECs). The collaborative team simultaneously produced C2+ products and hydrogen through water vapor-methane co-electrolysis in solid oxide electrolyzers, thereby improving atomic economy and system stability; by combining various in-situ characterization techniques, they systematically elucidated the mechanism of methane oxidation coupling reaction at the anode. The relevant results were published in German Applied Chemistry. Methane (CH4), as the main component of shale gas, is a raw material gas that is abundant in supply and low in cost. The efficient conversion of methane into high-value C2+ products is of great significance for energy utilization and industrial production. However, traditional oxidative coupling and anaerobic coupling processes face issues such as over-oxidation and carbon deposition, respectively, which limit their further development. Therefore, developing a methane conversion method with high atom economy and good stability holds significant scientific importance and practical value. In this work, the research team utilized a solid oxide electrolyzer to combine anodic methane coupling with cathodic water vapor electrolysis, thereby proposing a new system for the simultaneous and efficient production of C2+ compounds and hydrogen. At a current density of 127 mA cm?2, the system operated stably for over 90 hours, with a C2+ hydrocarbon selectivity of over 75% and an ethylene selectivity of about 40%, without any carbon deposition observed. In-situ Raman spectroscopy and near-atmospheric pressure XPS results indicate that oxygen ions are transported from the electrolyte to the Ag surface under voltage drive to generate active electrochemical overflow oxygen species (ESO), and methane reacts with ESO to produce methyl radicals (?CH3). The DFT results further indicate that the ESO on the Ag surface promotes methane adsorption activation and reduces the energy barrier for methane C-H bond cleavage. Synchrotron radiation photoionization mass spectrometry results indicate that methyl radicals on the electrode surface rapidly desorb into the gas phase, where they undergo gas-phase coupling to form ethane, which is then dehydrogenated to produce ethylene. This work provides direct experimental evidence for the presence of gaseous methyl radicals in electrochemical methane coupling. This study proposes a new reaction scheme for the co-electrolysis of water vapor and methane using SOEC to produce C2+ products and hydrogen, offering a new approach for the efficient conversion of methane. Furthermore, this study also details the \"surface activation-gas phase coupling\" reaction mechanism of anodic methane oxidation coupling, providing a basis for the design of anodic methane conversion catalysts and the optimization of reaction engineering.