Liquid metal–induced low-temperature synthesis of tunable high-entropy oxides

Abstract

High-entropy oxides (HEOs) have attracted attention due to their unique elemental synergistic effect and lattice distortion. However, mixing elements’ vastly different radii and valences leads to substantial element segregation during the reaction. In addition, the requirement for a harsh temperature (1100°C) to achieve entropy stabilization results in the volatilization of low–melting point components. Here, we propose a strategy for synthesizing functionalized Ga-based HEOs (GHEOs) at a low temperature (400°C) by the Ga integration mechanism. The negative mixing enthalpy between Ga and other metals reduces the Gibbs free energy, enabling the creation of homogeneous GHEOs through a hydrothermal process at a lower temperature. The Ga integration mechanism is supported by thermodynamic and density functional theory analyses. In particular, the perovskite, spinel, and rock salt crystal can be precisely tuned by choosing metal ions, enabling tailored applications in electrocatalysis, energy-saving materials, and methane sensors. Hence, this GHEOs strategy can be extended to realize many ideal GHEOs adjusted for specific applications.