Recent advances in high-entropy oxides: Composition modulation, morphology control, and catalytic applications

High-entropy oxides (HEOs) have emerged as a promising platform for advanced catalysis owing to their unique structural features, tunable elemental compositions, adjustable functionalities, and four typical synergistic multi-element effects. This review systematically covers HEOs from their fundamental definitions to practical applications, focusing on chemical composition modulation and morphology control through various synthesis approaches that enable precise tailoring of HEO structures. It also analyzes the catalytic performance of HEOs in thermocatalysis, photocatalysis, electrocatalysis, and their synergistic catalytic processes, highlighting their distinct advantages of high catalytic activity, abundant active sites, and exceptional stability. Finally, key challenges and future directions for HEO-based catalysts are outlined, aiming to inspire research efforts in the rational design of HEOs with tailored compositions and morphologies for specific catalytic applications. This review systematically summarizes high-entropy oxides (HEOs) from fundamental definitions to practical applications, focusing on their composition modulation, morphology control, catalytic performances in various fields. Additionally, it outlines key challenges and future research directions for HEO-based catalysts. • The unique structural features and four characteristic enhancement mechanisms of HEOs are introduced. • The classification of the functional roles of key metal elements in HEOs and their implications for applications is discussed. • The morphological control of HEOs, the collaborative optimization of synthesis, and the correlation between structural descriptors and performance were discussed. • The applications and performance regulation mechanisms of HEOs in thermo-/photo-/electro-catalysis and synergistic processes are summarized. • The advantages of HEOs catalysts and the current challenges were discussed, and the future trends were prospected.