Methane Decomposition Enabled by Molten Alkali Chloride Electrolysis

Abstract

Methane pyrolysis is a promising technology for producing value-added chemicals without CO₂ emission. Yet, its large-scale application is impeded by the harsh reaction conditions and the rapid deactivation of conventional solid catalysts. Herein, we present an electrochemical approach for efficient and stable methane decomposition within a molten alkali chloride salt system at temperatures between 400 and 660 °C. As the bubbles containing methane rise along the reactor column, the molten salt electrolysis enables the functionalization of methane through chlorination near the anode and the subsequent reduction into high-value chemicals either by a liquid reactive metal at the cathode or by solvated electrons. This process leads to the production of valuable chemicals such as hydrogen, ethylene, and carbon, and also regenerates the alkali chloride, closing a chlorine cycle. A systematic study was performed to unravel the key parameters that govern the performance of CH₄ decomposition. During a 100 h stability test at 1 A current and 550 °C temperature, the methane decomposition exhibited approximately 30% methane conversion, 70% hydrogen selectivity, and 5.3% ethylene selectivity in a molten salt electrolyzer with LiCl–NaCl–KCl electrolyte. This electrochemical process represents a versatile and effective technology for converting natural gas feedstock into more valuable chemicals.