Solid oxide cells (SOCs) hold great promise for clean energy conversion, yet conventional cathodes such as La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) suffer from insufficient electrocatalytic activity and poor CO₂ tolerance. This study designed a high-entropy perovskite, La_0.2Sr_0.2Pr_0.2Nd_0.2Ba_0.2Co_0.2Fe_0.8O_3–δ (HELSCF), via A-site high-entropy modification of LSCF. By regulating the synthesis temperature, two distinct crystal structures were achieved: an asymmetric tetragonal phase (HELSCF-Pbnm) with enhanced lattice distortion obtained at 1000 °C and a symmetric cubic phase (HELSCF-Pm3m) obtained at 1100 °C. Comprehensive characterizations confirmed that HELSCF-Pbnm exhibits superior properties, including a higher specific surface area, increased oxygen vacancy concentration, and optimized electronic structure. At 750 °C, the HELSCF-Pbnm-based symmetric cell delivers the lowest area-specific resistance of 0.040 Ω·cm², along with excellent bifunctional activity toward both the oxygen reduction reaction and oxygen evolution reaction, as well as outstanding tolerance under CO₂-containing atmospheres. When employed as the cathode in a single cell, it achieves a maximum power density of up to 1.38 W·cm⁻², approximately 1.7 times that of LSCF. Furthermore, it demonstrates exceptional operational stability for over 260 h at 600 °C. Density functional theory calculations further reveal that the orthorhombic structure enhances O₂ adsorption and d–p orbital hybridization, synergistically boosting catalytic performance. A temperature-modulated high-entropy strategy offers a facile and effective route for developing high-performance, CO₂-tolerant cathodes for reversible SOCs.

Developing high-performance cathodes is critical to advancing proton-conducting solid oxide fuel cells (PCFCs). However, their practical application remains constrained by sluggish oxygen reduction reaction (ORR) kinetics and the instability of nanoscale catalytic features in oxidizing environments. Here, a cobalt-free nanocomposite cathode is rationally engineered via a Mo-induced ion-topological strategy based on the perovskite oxide BaCe_0.26Ni_0.1Fe_0.64O_3−δ (BCNF10). Through the introduction of B-site Mo, the spontaneous exsolution of highly dispersed NiO nanoparticles significantly enhances surface oxygen exchange kinetics and leads to the formation of stable and well-defined heterointerfaces. The single cell with the optimized composite cathode Ba_0.95Ce_0.25Ni_0.1Mo_0.05Fe_0.6O_3−δ (BCNMF10) achieves an outstanding maximum power density (MPD) of 2002 mW·cm⁻² at 700 °C, accompanied by excellent long-term operational durability and humidity tolerance. First-principles calculations further elucidate the underlying mechanism, revealing a thermodynamically favorable, defect-mediated pathway for NiO formation and underscore the crucial role of dopant‒defect interactions in tailoring surface reactivity. This work provides a robust and scalable framework for the development of durable, high-efficiency cathodes for next-generation PCFCs.

One potential solution to the problems of energy storage and conversion is the use of reversible protonic ceramic electrochemical cells (R-PCEC), which are based on the solid oxide fuel cell (SOFC) technology and offer a flexible route to the generation of renewable fuels. However, the R-PCEC development faces a range of significant challenges, including slow oxygen reaction kinetics, inadequate durability, and poor round-trip efficiency resulting from the inadequacy of an air electrode. To address these issues, we report novel B-sites doped Pr_0.5Ba_0.5Co_0.7Fe_0.3O_3−δ (PBCF) with varying amounts of Sn as the air electrode for R-PCEC to further enhance electrochemical performance at lower temperatures. At 600 ℃, R-PCEC with an air electrode consisting of Pr_0.5Ba_0.5Co_0.7Fe_0.25Sn_0.05O_3+δ has achieved peak power density of 1.12 W∙cm⁻² in the fuel cell mode and current density of 1.79 A∙cm⁻² in the electrolysis mode at a voltage of 1.3 V. Moreover, R-PCECs have shown good stability in the electrolysis mode of 100 h. This study presents a practical method for developing durable high-performance air electrodes for R-PCECs.