Exsolved medium-entropy alloy FeCoCuNi in titanate fibers enables solid oxide cells with superb electrochemical performance†

Solid oxide cells (SOCs) are dual-functional electrochemical devices for energy storage and conversion, offering flexibility and high efficiency. It is important to improve the catalytic activity of electrodes and to increase the redox stability of interfaces for their application. Herein, hemp rope-like nanofibers with exsolved medium-entropy-alloy (MEA) are fabricated by in situ growth of an anchored MEA/oxide interface on La_0.4Sr_0.4Ti_0.9(Fe_0.25Co_0.25Cu_0.25Ni_0.25)_0.1O_3−δ (LSTFCCN) perovskite electrodes, delivering remarkably enhanced electrochemical activity under a variety of complex fuels both in fuel cell (FC) mode and electrolysis cell (EC) mode. The cell has a high peak power density of 1.01 W cm⁻² in FC mode using H₂ as the fuel and a high current density of 1.52 A cm⁻² at 1.60 V in the CO₂–H₂O co-electrolysis mode at 800 °C. In particular, theoretical calculations reveal that the exsolved metal cluster significantly decreases the reaction energy barrier of the CO₂RR and Methane Oxidation Reaction (MOR) by promoting the charge transfer between the adsorbed molecule and bulk, thereby markedly improving the electrochemical properties of the cell. We demonstrated a novel and effective approach for enhancing the catalytic performance of electrodes in SOCs, with the aim of inspiring further advancements in the development of multifunctional SOCs.