Electrocatalytic Oxidative Coupling of Methane on NiFe Exsolved Perovskite Anode: Effect of Water

Oxidative coupling of methane (OCM) can be performed electrocatalytically by utilizing solid oxide cells, which provide a readily controlled oxygen supply through dense electrolytes. La0.7Sr0.2Ni0.2Fe0.8O3 (LSNF) perovskite is an effective anode for OCM. Its surface characteristics and electrocatalytic activity can be improved by reduction and the resultant exsolution of bimetallic NiFe nanoparticles from its bulk. X-ray diffraction (XRD) and environmental transmission electron microscopy proved that the evolution of hetero-phases under reducing environment resulted in bimetallic NiFe nanoparticles being formed on the surface. A 36 % improvement in C2+ hydrocarbon production rate was achieved due to the reduction of LSNF with the exsolved NiFe nanoparticles. Co-feeding of H2O enhanced selective conversion of CH4 resulting in the production rate of C2+ hydrocarbons being increased by 56 %. Analysis of impedance spectra and in-situ DRIFTS under a CH4+H2O atmosphere provided an understanding for the enhancement on the electrocatalytic OCM.