High-entropy oxides (HEOs) have emerged as a groundbreaking class of materials in electrocatalysis, offering unparalleled compositional flexibility, synergistic multi-element effects, and exceptional stability. This review comprehensively explores the recent advances in HEOs, focusing on their unique properties, synthesis strategies, and electrocatalytic applications. We delve into the fundamental principles of HEOs, including high-entropy effects, lattice distortion, and cocktail effects, which underpin enhanced catalytic performance. Advanced synthetic methods, such as solid-state, liquid-phase, and gas-phase techniques, were systematically analyzed to customize the morphology, crystallinity, and active sites of hydroxide ions. Furthermore, we highlight the applications of HEOs in critical electrochemical reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR), and other emerging catalytic reactions, emphasizing their superior activity and durability over conventional catalysts. Density functional theory (DFT) insights into active site modulation and reaction mechanisms are integrated to bridge experimental observations with theoretical understanding. Finally, we address current challenges and propose future directions for optimizing HEOs. This review aims to inspire innovative strategies for developing next-generation HEO-based electrocatalysts to meet global energy and sustainability demands.

Zinc-ion hybrid capacitors (ZHCs) combine the merits of zinc ion batteries and supercapacitors, have attracted increasing attention due to cost-effectiveness, improved safety, high energy/power densities, long-term electrochemical stability, and ease of assembling. As one type of promising electrode material for ZHCs, MXene-based materials have drawn wide research because of their adjustable layer spacing, excellent physical and chemical properties, high conductivity and good electrochemical stability. In recent years, massive research on improving the energy density and cycle stability of ZHCs, and the modification and optimization of MXene have provided a new way to enhance the performance of ZHCs. In this paper, we briefly introduce the basic information about MXene, review several preparation methods of MXene, and emphasis on the modification and utilization of MXene in the cathodes, anodes and electrolyte of ZHCs. In addition, the utilization of MXene in ZHCs separators is also displayed. Eventually, the promising future and challenges of MXene-based materials for ZHCs applications are outlined.