Efficient electrochemical methane coupling enabled by stabilized oxygen species

The electrochemical oxidative coupling of methane (EOCM) integrated with CO₂ electrolysis in solid oxide electrolyzers (SOECs) is a promising approach for methane utilization and achieving carbon neutrality. However, the progress in methane activation is hindered by low C₂ product selectivity and limited reaction activity, mainly due to the lack of efficient and stable catalysts and rational design strategies. Current research focuses on developing catalysts that can stabilize reactive oxygen species to facilitate C–H bond activation and subsequent C–C bond formation.

This study presents a novel composite electrode composed of perovskite La_0.6Sr_0.4MnO_3–δ and Ce-Mn-W materials, supported by (Ce_0.90Gd_0.10)O_1.95. The electrode design leverages oxygen species engineering and interfacial synergy to enhance electrochemical methane coupling efficiency. Theoretical and experimental investigations reveal that this composite electrode stabilizes active oxygen species during the oxygen evolution reaction (OER) and exhibits superior methane adsorption capability.

The composite electrode demonstrated remarkable performance in EOCM. At 850 °C, the CMW@GDC/LSM electrode achieved a highest methane to C₂ production rate of 626 μL/min/cm² and a highest C₂ product selectivity of 80.3%. The study also explored the influence of methane partial pressure and flow rate on the reaction rate, providing deeper insights into the EOCM mechanism. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) results confirmed the superior activity and stability of the composite electrodes. The highest C₂ product selectivity of 80.3% was achieved at 100 mA/cm², decreasing to 52.89% at 600 mA/cm² due to increased oxygen flux and overoxidation tendencies.

This work establishes a new paradigm for designing high-activity and durable EOCM catalysts. The oxygen species engineering and interfacial synergy strategy not only enhances the efficiency of methane conversion but also advances the foundational framework for SOEC applications in low-carbon energy conversion. The incorporation of CO₂ electrolysis at the cathode contributes to carbon neutrality efforts. While methane conversion remains moderate, strategies such as developing large-scale stack cells with larger catalyst specific areas could overcome current limitations.