Electrocatalytic surface nanoionics with strained interfaced and colossal conductivity for enhancing durability and performance of solid oxide fuel cell

Abstract

For an oxygen electrode in solid oxide fuel cells (SOFCs) consisting of mixed electrical and ionic conducting lanthanum strontium cobalt ferrite (LSCF), it degrades due to its low chemical stability and cation surface segregation. To mitigate such degradation, for the first time in the field of SOFCs, we demonstrate a conformal ultra-thin (∼10 nm) coating consisting of subjacent discrete nano-Pt capped with a superjacent conformal CoO x layer, applied on LSCF/SDC composite electrode, using atomic layer deposition (ALD). The coating layer reduces the cell series resistance by up to 40%, presents extraordinary stability with an intact morphology after 816 h operation. The superjacent CoO x surface nanoionics consists of randomly orientated but single-layered nanograins, with high-density intergranular and surface grain boundaries serving as the electrochemical reaction sites and facilitating mass transport. The ALD coating turns the original perovskite surface that is vulnerable to cation segregation and degradation into an embedded strained interface phase with enormous conductivity. The coating layer appears to suppress Sr outward diffusion and confines a 2 nm Sr-enriched interface layer between the coating layer and the LSCF backbone. The conductivity of the coating layer is estimated to be ∼1.27 × 10 4 S/cm and two orders magnitude higher than that of LSCF. • Conformal CoO x nanoionics with discrete Pt nano-particles on LSCF/SDC. • Heterogeneous CoO x /Pt reduces the cell series resistance by 40%. • CoO x /Pt ALD layer possesses extraordinary nanostructure stability over 816 h. • CoO x /Pt ALD layer suppresses Sr outward diffusion. • Conductivity of the ALD layer is two orders magnitude higher than that of LSCF.