Carbothermal Shock Synthesis of Multimetallic, Solid Solution Electrocatalysts for Air-Based Batteries

Abstract

Multicomponent nanomaterials are extremely difficult to synthesize by conventional methods. Accordingly, nanoparticles composed of immiscible elemental combinations tend to phase-separate rather than form singe-phase solid solutions, which limits the compositional space. A synthetic technique that facilitates kinetic control over thermodynamic mixing regimes is therefore advantageous and offers untold scientific and technological opportunities. Here, we present a general route to alloy up to eight dissimilar elements into high entropy alloy nanoparticles (HEA-NPs) through a facile and tunable synthesis method: carbothermal shock (CTS).1 CTS employs flash heating and cooling of metal precursors on carbon to produce multimetallic nanoparticles with tailored elemental compositions, particle sizes, and structural complexity. Uniform mixing of nearly any metallic combination is achieved through high temperature exposure (~2000 K) during the thermal shock (55 ms) process, while rapid quenching (~105 K/s) retains this high-entropy state to form single-phase solid solutions. This new synthetic technique promotes materials discovery and design for a wide range of applications, including catalysis and energy storage. Inspired by the performance of quinary HEA-NPs as ammonia oxidation catalysts, novel solid solution nanoparticles (with 2 or more metallic elements) are synthesized and evaluated as electrocatalysts in air-based batteries, such as lithium-oxygen (Li-O2) and Li-CO2. In this way, HEA-NPs composed of catalytically active elements may impart synergistic electrocatalytic effects to improve overall battery performance. This talk will describe the process and underlying mechanism to synthesize HEA-NPs, the overall capabilities of the CTS method, and recent results on electrocatalyst development towards Li-air battery applications.