High-Entropy Driven Self-Assembled Dual-phase Composite Air Electrodes with Enhanced Performance and Stability for Reversible Protonic Ceramic Cells

Abstract

Reversible proton ceramic cells (R-PCCs) offer a transformative solution for dual functionality in power generation and energy storage. However, their potential is currently obstacles by the lack of high-performance air electrodes combining high electrocatalytic activity with durability. Here, an innovative air electrode composed of high-entropy driven self-assembled xNiO-Pr_0.2La_0.2Ba_0.2Sr_0.2Ca_0.2Fe_0.8Ni_0.2−xO_3−δ (N-XFN) composites is presented, which result from the unique lattice distortion effects inherent in high-entropy perovskites. The experimental results coupled with density functional theory (DFT) calculations verify that the lattice distortion at the high-entropy A-site significantly induces NiO nanoparticles exsolved from the B-site, promoting the formation of a biphasic composite structure that dramatically increases the electrochemical active sites. Remarkably, R-PCCs using the N-XFN composite air electrode achieve an impressive peak power density of 1.30 W cm⁻² in fuel cell mode and a current density of -2.52 A cm⁻² at 1.3 V in electrolysis mode at 650 °C. In addition, the cells show excellent stability with reversibility over 830 h, including 500 h in electrolysis mode and 330 h in reversible operation at 650 °C. This research provides important insights into the design of high-entropy perovskites, paving the way for advanced R-PCCs technology.