Enhanced Ni Exsolution in High-Entropy Perovskite Oxides with Broadening of Migration-Reduction Energy Landscapes

While high-entropy perovskite oxides have recently emerged as promising hosts for exsolution-enabled catalysts and electrodes, a systematic understanding of how high-entropy compositions influence exsolution remains limited. Here, we compare Ni exsolution in a simpler perovskite oxide, (La0.6Sr0.4)0.95(Co0.19Fe0.76Ni0.05)O3−δ (LSCF-5Ni), and two high-entropy perovskite oxides, (La0.2Sr0.2Ca0.2Nd0.2Y0.2)0.95(Co0.19Fe0.76Ni0.05)O3−δ (CaNdY-5Ni) and (La0.2Sr0.2Ba0.2Nd0.2Y0.2)0.95(Co0.19Fe0.76Ni0.05)O3−δ (BaNdY-5Ni). The experiment reveals that the exsolved nanoparticle number density follows the order LSCF-5Ni < CaNdY-5Ni < BaNdY-5Ni, demonstrating that high-entropy configurations can enhance exsolution. To understand this trend, we develop a Monte Carlo-based modeling framework that combines a machine-learned interatomic potential to simulate representative atomic configurations and statistically evaluate possible exsolution pathways. The results show that high-entropy configurations with greater variations in A-site cation sizes (and thus greater lattice distortions) can broaden distributions of Ni migration and reduction energies, thereby creating more thermodynamically favorable exsolution pathways.