Perovskite-Triggered Dual Exsolution of Oxygen-Deficient CeO2 Matrix and NiFe Nanoalloys for Enhanced CO2 Electrolysis

Abstract

Perovskite cathodes for CO₂ electrolysis offer excellent redox stability but suffer from limited activity. Although in situ exsolution of B-site cations is a powerful strategy to alleviate this issue, this process often triggers co-segregation of insulating AO_x phases, which diminishes active site exposure and ionic-electronic conductivity. Here we addressed the critical issue of insulating phase segregation in conventional exsolved perovskite by developing a Ce-doping strategy in Sr_1.95Ce_0.05Fe_1.3Ni_0.2Mo_0.5O_6−δ (SCeFNM). This material, upon annealing in reducing atmosphere, allowed in situ construction of nanoscale CeO₂-NiFe/oxide heterostructures (CeO₂-NiFe@SCeFNM) by co-exsolving oxygen-deficient CeO₂ phase and NiFe alloy nanoparticles (NPs) on the surface. The unique architecture achieved a high current density of 1.57 A cm⁻² at 1.5 V and 850 °C with a CO Faradaic efficiency over 96%, outperforming NiFe@SFNM and their counterparts. Combined results demonstrated that the superior activity mainly came from the synergy within the “three-in-one” heterostructure, where NiFe alloy NPs rose the electronic conductivity, and CeO₂ phase extended the O²⁻ migration channels capable of enhancing CO₂ adsorption and activation, while perovskite backbone ensured the structural integrity. This study establishes a universal paradigm for constructing advanced catalysts for diverse applications via co-exsolution of metal NPs and defective oxide phases from appropriately A-site-doped perovskites.