Beyond Single-Active Sites: The Emergence of High-Entropy Perovskites in Energy and Environment Catalysis

High-entropy perovskites (HEPs) have emerged as a transformative class of multicomponent oxides that extend beyond the limitations of conventional single-active-site perovskites for sustainable energy and environmental catalysis. Configurational entropy provides single-phase structures by incorporating five or more cations into the ABO₃ lattice, creating a wide range of local coordination environments, tunable electronic structures, and synergistic catalytic sites. This review summarizes recent advances in entropy engineering strategies, including A-site, B-site, and dual-site disorder, alongside key thermodynamic descriptors governing phase stability and lattice distortion. We further discuss established and emerging synthesis routes, from sol-gel and solid-state reaction to field-assisted and ultrafast methods, highlighting their advantages for compositional homogeneity and scalable production. Density functional theory, special quasirandom structures, and thermodynamic modeling are studied to provide computational understanding of stabilization and catalytic descriptors. Particular emphasis is placed on energy and environmental applications, including water splitting, oxygen reduction, CO₂ reduction, ammonia decomposition, fuel cells, solar cells, and pollutant degradation, where HEPs demonstrate enhanced activity, durability, and resistance to scaling-related limitations. Finally, key challenges in compositional complexity, mechanistic understanding, and sustainable synthesis are outlined, along with future opportunities in nonequimolar design, multianion engineering, and scalable fabrication for next-generation entropy-stabilized catalysts.