Anodic Shock-Triggered Exsolution of Metal Nanoparticles from Perovskite Oxide.

Nanoparticles decorated electrodes (NDEs) are useful in fuel cells, electrolyzers, water treatment, and chemical synthesis. Here, we show that by rapidly bringing a mixed ionic-electronic conductor outside its electrochemical stability window, one can achieve uniform dispersion of metallic nanoparticles inside its bulk and at the surface and improve its electrocatalytic performance when back under normal functional conditions. Surprisingly, this can happen under anodic as well as cathodic current/voltage shocks in an ABO perovskite oxide, LaCaTiFeNiO (LCTFN), across a wide range of H/O gas environments at 800 °C. One possible mechanism for bulk Fe/Ni precipitation under anodic shock condition is the incomplete oxygen oxidation (O → O, 0 < α < 2), migration and escape of oxygen to interfaces, and "whiplash" transition-metal reduction due to low electronic conductivity. We show that both cathodic and anodic shocks can produce NDEs to enhance electrocatalytic performance, potentially improving the flexibility of this approach in practical devices.