Fundamental comprehension, synthetic procedures and catalytic applications of high entropy oxide nanomaterials

Improve existing catalyst systems and create new catalytic nanomaterials via high entropy design strategy has been an emerging topic in field of material. High entropy oxides (HEO) possess unique properties, resulting in a complexity of the localized environments and expected wide adjustability, owing to the "cocktail" effect. However, oxides exhibit quite different behavior to their characteristics after the replacement of >= 5 elements in cation sites comparing to the condition of alloy. The practical applications of HEO nanomaterials are still lack of breakthrough in catalysis and remain largely unexplored. Limited understanding of HEOs, no matter the microscopic disordered composition or the mechanism behind, is primarily responsible for these problems. Herein, we demonstrate the fundamental comprehension of high entropy oxides from a structural perspective. Generally, synthetic procedures, catalytic applications and the complementation with single atoms of HEOs are elaborated in detail. Representative strategies to theoretically predict and screen the potential HEOs against the massive combinations of elements are discussed in this review. Furthermore, we predict short-term and long-term directions and present our perspectives with regards to design strategies and synthesis novel HEO based catalysts in the future.