A highly efficient and stable perovskite cathode with in situ exsolved NiFe alloy nanoparticles for CO2 electrolysis

Abstract

Perovskite structured oxides are promising candidate cathode materials for solid oxide electrolysis cells (SOECs) due to their better redox stability and coking resistance than nickel–yttria stabilized zirconia. The present study aimed at improving the CO₂ electrolysis performance of the lanthanum chromium ferrite cathode through modification with metal nanoparticle catalysts. NiFe nanoparticles were exsolved from (La_0.75Sr_0.25)_0.95Cr_0.5Fe_0.35Ni_0.15O_3−δ (LSCrFN) upon exposure to hydrogen at 800 °C. For comparison, NiFe nanoparticles were also deposited on La_0.75Sr_0.25Cr_0.5Fe_0.5O_3−δ (LSCrF) using the infiltration method. When used as a supporting cathode for SOECs, the one with the exsolved nanoparticles exhibited a higher CO₂ electrolysis current density than the one with the infiltrated nanoparticles and the one without the nanoparticles, e.g., their corresponding current densities at 1.5 V and 800 °C were 1.15, 0.80, and 0.59 A cm⁻². The electrode with the exsolved nanoparticles also demonstrated much better durability than that with the infiltrated nanoparticles. When tested at 1 V and 800 °C, the current density of the former decreased from 0.66 to 0.63 A cm⁻² during a period of 260 h, i.e., 0.012% h⁻¹, and the nanoparticles remained well dispersed after the test. In contrast, for the latter, the current density dropped from 0.33 to 0.29 A cm⁻² within 26 h, i.e., 0.15% h⁻¹, and severe agglomeration of the nanoparticles occurred. It is concluded that perovskite oxides modified with the exsolved metal nanoparticles possess both high electrocatalytic activity and stability, promising for use as the supporting cathode for SOECs.