Voltage-Temperature Co-Tuned Exsolution for <i>In Situ</i> and Rapidly Improving Electrochemical Activity of Perovskite Oxide

Exsolution catalysts on perovskite oxides are useful in electrochemical energy conversion processes. Here, we report that the size and density of the exsolved metal nanoparticles can be manipulated by co-tuning the temperature and voltage in operando, to improve the electrocatalytic activity of perovskite oxides. We show that the population density of the exsolved particles increases with shock voltage at a constant temperature. In addition, the size of the exsolved metal nanoparticles decreases and the number density increases upon voltage shock when the exsolution takes place at lower temperatures, due to higher nucleation rate and lower growth rate of nanoparticles. The perovskite oxide with the smaller size and higher density of exsolved catalysts shows the highest relative enhancement in electrocatalytic activity. For example, a factor of ∼15× enhancement of the peak power density is achieved after voltage shock at a relatively low temperature of 700 °C. The ability to tune the particle size and population density as well as the electrocatalytic activity in operando improves the flexibility of the application of the exsolution-based materials inbut not limited tofuel cells.