Controlling exsolution with a charge-balanced doping approach

While exsolution is widely observed among perovskite hosts as an attractive technique for in-situ catalyst synthesis, our current understanding of the complex exsolution-host relationships is solely based on the conventional approach of using a small amount of a single dopant at a limited high-temperature range (≥ 800 °C). Herein, we develop a charge-balanced double-doping approach that opens new doors for the synthesis of a wide range of compositions, and the highly tunable nature of these compositions provides a basis for controlling exsolved particle size, distribution, composition, and surface anchorage. Against the conventional wisdom that high doping level leads to unstable exsolution, we show that increased double-doping levels, enabled by our novel method, can stabilize the perovskite phase in reducing conditions to provide high conductivity (> 35 S/cm) at low temperatures (450–650 °C) and exsolve smaller, more densely populated particles with different chemistry than their lightly doped analogues. Furthermore, we find that associated defects might be the main factor that determines nucleation sites, and the conductivity of the host may play a crucial role in exsolution kinetics by facilitating cation transport. This study paves the way for controlling exsolved electrocatalyst properties by engineering the charge-balanced B-site and offers new knowledge that links exsolution to defect chemistry.