Highly Active Air Electrode with Enhanced Proton Conduction via Isovalent Doping in a Layered Perovskite for Reversible Protonic Ceramic Cells

Abstract

Reversible protonic ceramic cells (R-PCCs) offer a compelling solution for efficient energy conversion and storage at intermediate temperatures (400-600 degrees C); however, their practical implementation and overall electrochemical performance are severely constrained by sluggish electrochemical reaction kinetics at the air electrode. Herein, a novel triple ionic-electronic conducting material is presented, the Ni-doped layered perovskite PrBa0.5Sr0.5Co1.8Ni0.2O5+delta (PBSCN20), to be utilized as an air electrode in R-PCCs. Thermogravimetric analysis and density functional theory calculations demonstrate that Ni doping at the Co site significantly promoted oxygen vacancy formation while simultaneously facilitating proton uptake and migration. Consequently, the R-PCCs with a PBSCN20 air electrode exhibited outstanding electrochemical performance, attaining peak power densities of 1.30 and 0.60 W cm-2 in fuel cell mode, and current densities of -1.72 and -0.41 A cm-2 at 1.3 V in electrolysis mode at 600 and 500 degrees C, respectively, as well as superior long-term stability for over 700 h at 500 degrees C.