Confinement effects in photocatalysis: progress and challenges

With the continuous growth of global energy demand and increasingly serious environmental pollution problems, photocatalytic technology, as an effective method for converting solar energy into clean hydrogen energy, has great potential in energy conversion and environmental purification. However, traditional photocatalytic materials have problems such as high recombination rate of photo-excited electrons and holes, poor adsorption capacity of reactants, and low utilization rate of catalytic active sites. The confinement effect effectively enhances the catalytic efficiency by restricting the active species to the nanoscale region through a special spatial structure. This review first introduces one-dimensional, two-dimensional, and three-dimensional confined structures and then summarizes the application of confinement effects in wastewater treatment, air pollutant treatment, photocatalytic H₂ or H₂O₂ production and photocatalytic CO₂ reduction in recent years, focusing on analyzing the reaction mechanism and the reasons for the improvement of catalytic performance. Finally, several outlooks for future research on the confinement effects are proposed.