Interfacial redox reaction-directed synthesis of silver@cerium oxide core–shell nanocomposites as catalysts for rechargeable lithium–air batteries

Abstract

A facile oxidation–reduction reaction method has been implemented to prepare pomegranate-like Ag@CeO2 multicore–shell structured nanocomposites. Under Ar atmosphere, redox reaction automatically occurs between AgNO3 and Ce(NO3)3 in an alkaline solution, where Ag+ is reduced to Ag nanopartilces and Ce3+ is simultaneously oxidized to form CeO2, followed by the self-assembly to form the pomegranate-like multicore–shell structured Ag@CeO2 nanocomposites driven by thermodynamic equilibrium. No other organic amines or surfactants are utilized in the whole reaction system and only NaOH instead of organic reducing agent is used to prevent the introduction of a secondary reducing byproduct. The as-obtained pomegranate-like Ag@CeO2 multicore–shell structured nanocomposites have been characterized as electro-catalysts for the air cathode of lithium–air batteries operated in a simulated air environment. Superior electrochemical performance with high discharge capacity of 3415 mAh g−1 at 100 mA g−1, stable cycling and small charge/discharge polarization voltage is achieved, which is much better than that of the CeO2 or simple mixture of CeO2 and Ag. The enhanced properties can be primarily attributed to the synergy effect between the Ag core and the CeO2 shell resulting from the unique pomegranate-like multicore–shell nanostructures possessing plenty of active sites to promote the facile formation and decomposition of Li2O2.