High-entropy compounds for photo(electro)catalysis: diverse materials and applications

High-entropy compounds (HECs), which are characterized by integrating five or more principal metallic or non-metallic elements within a crystallographic lattice through their multi-component structures, have drawn significant attention in the materials science community. These materials are renowned for their remarkable chemical and structural stability, enabling their robust performance under a variety of challenging conditions. Notably, HECs possess four core effects and adjustable electronic and band structures, along with an abundance of active sites, making them prime candidates for advancements in photo(electro)catalytic technologies. The unique attributes of HECs are essential for the creation of next-generation, high-efficiency photo(electro)catalytic materials. This review offers an in-depth examination of the state-of-the-art research, outlining the potential applications and addressing the current challenges of HECs in the realms of photocatalysis, electrocatalysis, and photoelectrocatalysis. It begins with an elucidation of the fundamental structural features, physicochemical properties, and the diverse classification of HECs, including oxides, chalcogenides, nitrides, oxynitrides, carbides, silicides, borides, fluorides, phosphides, hydroxides, and metal-organic frameworks. Subsequently, it transitions into a detailed exploration of the most recent research advancements of HECs in photo(electro)catalytic applications, covering crucial areas such as water splitting, carbon dioxide conversion, nitrogen fixation, ammonia reduction, pollutant degradation, and energy storage. Additionally, this review emphasizes the primary challenges currently faced by the field, providing critical insights into the limitations and potential solutions for overcoming these obstacles.