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Reversible proton‐conducting solid oxide cells (R‐PSOCs) are considered to be one of the most promising devices for efficient power generation and hydrogen production. However, the requirement of high catalytic activity for fast oxygen reduction/evolution reaction (ORR/OER) and durability under high steam concentration of air electrode materials remains the major challenge for the practical application of R‐PSOCs. Here, a series of cobalt‐free Ruddlesden–Popper perovskite of Nd0.8Sr1.2Ni1‐xFexO4±δ are reported with mixed conductivity for enhanced ORR/OER kinetics. The R‐PSOCs with an optimal Nd0.8Sr1.2Ni0.7Fe0.3O4±δ air electrode show a high peak power density of 1.28 W cm−2 in the fuel cell mode and a promising current density of 3.24 A cm−2 at 1.3 V in the electrolysis cell mode at 700 °C. In addition, the R‐PSOCs show favorable stability under the fuel cell, electrolysis, and reversible modes for hundreds of hours. This work demonstrates that the Ruddlesden–Popper materials can be utilized as suitable air electrodes for R‐PSOCs. [ABSTRACT FROM AUTHOR]

The ternary copolymerization strategy has emerged as a promising strategy for developing high‐efficiency donor polymers in polymer solar cells (PSCs). Terpolymers based on the star polymer PM6 have already realized good photovoltaic performance. However, challenges such as the intricate synthesis of fluorine‐substituted benzodithiophene (F‐BDT) unit of PM6 and entropy increase induced by backbone disorder have hindered the construction of high‐performance donor terpolymers. In this work, these challenges are addressed by opting for the cost‐effective chlorinated‐substituted benzodithiophene unit (Cl‐BDT) as an alternative to F‐BDT and incorporating the large dipole moment and electron‐deficient TPD group as the third component into the high‐performance donor polymer of PM7. As expected, this approach effectively suppresses terpolymer backbone disorder while enhancing crystallinity, thereby optimizing morphology and improving charge generation and transport. Remarkably, the PM7‐TPD‐10‐based device with 10% TPD replacement achieves a champion power conversion efficiency (PCE) of 18.26%. After introducing PM7‐TPD‐10 as the third component into D18:L8‐BO blend, a dual mechanism for improving the efficiency to 19.40% is realized. This work demonstrates that the high dipole moiety as the third component to construct terpolymers is an important strategy to suppress the backbone disorder and increase the crystallinity, facilitating the optimization of morphology and device performance. [ABSTRACT FROM AUTHOR]

Insufficient catalytic activity and stability of oxygen electrodes are major challenges for the widespread use of reversible solid oxide cells (Re‐SOCs). Here, a Ruddlesden‐Popper‐structured high‐entropy La1.4Sr0.6Co0.2Fe0.2Ni0.2Mn0.2Cu0.2O4±δ (RP‐LSCFNMC) oxygen electrode with fast oxygen reduction and emission reaction kinetics, inhibited Sr segregation and favorable thermal expansion efficient is reported. A Re‐SOC with the RP‐LSCFNMC oxygen electrode achieves an encouraging peak power density of 1.74 W cm−2 in the fuel cell mode and a remarkable current density of 2.10 A cm−2 at 1.3 V in the water electrolysis mode at 800 °C. The Re‐SOC also shows excellent stability, with no Sr segregation observed after 120 h of testing in both the fuel cell and electrolysis modes at 750 °C. Furthermore, the improved activity and stability of the RP‐LSCFNMC oxygen electrode are confirmed through a combination of experiments and density functional theory‐based calculations. These findings make the high‐entropy RP‐LSCFNMC oxide a promising oxygen electrode candidate for advanced Re‐SOCs. [ABSTRACT FROM AUTHOR]