General synthesis of high‐entropy oxides and carbon‐supported high‐entropy oxides by mechanochemistry

High‐entropy oxides (HEOs) have been receiving a lot of attention due to their excellent properties. However, current common methods for preparing HEOs usually involve high‐temperature processes. The development of green synthesis techniques remains an important issue. Carbon‐supported HEOs have shown excellent performance in electrochemical energy storage in recent years. Crucially, the traditional methods cannot synthesize carbon‐supported HEOs under N2 or air atmospheres. Toward this end, a universal method for preparing carbon‐supported HEOs was proposed. During this process, without high‐temperature post‐treatment, high‐entropy LaMnO3 could be synthesized in 2 hours using the mechanical ball‐milling method. Furthermore, this method was universal and has been proved in the synthesis of a series of HEOs such as PrVO3, SmVO3, and MgAl2O4. The LaMnO3 species synthesized by this method exhibit excellent catalytic performance in CO combustion and could maintain a conversion rate of over 97% for 350 hours. Subsequently, carbon‐supported HEOs could be obtained with 0.5 hours of additional ball‐milling, offering significant advantages over traditional methods. This process provides a potential method to synthesize carbon‐supported HEOs.