Enhancing electrochemical methane coupling in solid oxide cells by tuning oxygen species in the catalyst

Abstract

Due to the rapid growth of shale gas production, the oxidative coupling of methane (OCM) to ethylene and ethane has attracted renewed interest. This process requires efficient catalysts capable of activating the first C–H bond of methane while inhibiting the complete dehydrogenation and over-oxidation to CO₂. Here, we successfully implemented OCM in a solid oxide cell, which can usually control the reaction process more accurately and reduce the generation of by-products. La-doped SrTiO₃ perovskite oxides (LST) with controlled formation of oxygen vacancies and lattice oxygen species were synthesized as anode materials for a solid oxide cell. By changing the ratio of La/Sr in the perovskite A-site, La_0.7Sr_0.2TiO_3−δ exhibited the best performance in terms of methane conversion and C₂ (ethane and ethylene) selectivity due to its highest oxygen evolution reaction activity, highest lattice oxygen content, and few oxygen vacancies. Density functional theory (DFT) calculations further confirmed that the activation of methane is more favorable to occur on the surface with less oxygen vacancies and more lattice oxygen, resulting in a significantly higher conversion rate. This work opens a new avenue for designing anode materials for methane-coupling in solid oxide cells.