Recent advances in graded nanomaterial-based photocatalysts: Principles, designs, and applications

The rise in global energy demand and environmental pollution highlights the importance of developing efficient and stable photocatalytic materials to address the energy crisis and environmental issues. Graded nanomaterials exhibit significant promise for photocatalysis due to their unique structural advantages, including multi-scale pores, high specific surface area, and optimized electron transport pathways. This review systematically examines the design principles and synthesis methods for hierarchical nanomaterials and their photocatalytic performance. Through modulation of porous structures, hierarchical heterojunctions, and core-shell configurations, graded nanomaterials notably improve light absorption efficiency, carrier separation, and surface reaction activity of photocatalysts. Strategies such as S-scheme heterojunctions and interface engineering further enhance the performance of photocatalysts for CO₂reduction, hydrogen production, and pollutant degradation. In situ characterization techniques offer dynamic insights into the photocatalytic mechanism. This study elucidates how hierarchical structures influence photocatalytic performance, discusses their potential applications in environmental treatment and clean energy, and proposes directions for future design and optimization of photocatalytic materials.