A general strategy for preparing hollow spherical multilayer structures of Oxygen-Rich vacancy transition metal Oxides, especially high entropy perovskite oxides

The development of excellent synthetic strategies and exploration of the synthesis mechanisms of active site-rich high-entropy oxides are crucial for high-entropy materials. Herein, a universal synthetic method was designed to prepare La(Co0.2Mn0.2Fe0.2Ni0.2Cu0.2)O3 (HSM-HEPs) with hollow spherical multilayer structure (HSM) and rich oxygen vacancies. The tracking characterization was used during the synthesis of HSM-HEPs to clarify the for-mation of multi-shell, multi-vacancy, and single-phase crystal structures of HSM-HEPs. Three basic conditions were proposed to obtain vacancy-rich high-entropy materials. The experimental data showed excellent elec-trochemical activity and extraordinary stability of HSM-HEPs electrode materials owing to the formation of HSM structure, abundant oxygen vacancies, abundant elemental composition, and high specific surface area. When used as supercapacitor electrode materials, HSM-HEPs exhibited a high specific capacity of 625 F g-1 with an excellent capacity retention rate of 88 % after 10,000 cycles. Besides, HSM-HEPs achieved efficient water oxidation with an overpotential of 309 mV at 10 mA cm-2. Furthermore, the proposed strategy can be extended to the synthesis of metal oxides with various representative HSM crystal structures. Overall, the designed and tuned synthetic method looks promising for the formation of more active sites-high-entropy materials.