Defect-engineered high-entropy oxides, sulfides, and oxynitrides: bridging configurational complexity with catalytic functionality

Abstract High-entropy inorganic solids have rapidly emerged as a transformative class of catalytic materials, distinguished by multication sublattices, severe lattice distortions, and entropy-stabilized phase complexity that collectively generate diverse and tunable active sites. Despite this progress, the literature remains fragmented, with limited integration of defect chemistry, local disorder, and dynamic surface reconstruction across oxide, sulfide, and oxynitride systems. This review presents a unifying inorganic-chemistry perspective on defect-engineered high-entropy oxides, sulfides, and oxynitrides for solar-driven and electrochemical energy conversion. It systematically elucidates the thermodynamic and electronic consequences of configurational entropy, alongside the formation, modulation, and catalytic roles of anion vacancies (O, S, N), cation disorder, lattice strain, and mixed-valence states. Synthetic strategies are critically evaluated in terms of their ability to precisely engineer these defect landscapes. Advanced ex situ, in situ , and operando characterization techniques are consolidated with emerging computational descriptors to decode active-site evolution under working conditions. Furthermore, the review establishes robust structure–performance relationships across key reactions, including photocatalytic hydrogen evolution, oxygen evolution, pollutant degradation, carbon dioxide reduction, and electrocatalytic OER, HER, and ORR. Critical challenges are identified in quantitative defect characterization, reproducibility, benchmarking protocols, and mechanistic clarity, alongside pathways toward scalable catalyst design. By bridging defect chemistry with catalytic functionality across multiple anion frameworks, this work delivers a cohesive and forward-looking blueprint for the rational design of next-generation high-entropy catalytic systems.