Spin Polarization‐Boosting Ultrafast Carrier Dynamics and Exciton Dissociation in Fe Nanoparticle‐Loading Graphitic Carbon Nitride Toward Efficient CO₂ Photoreduction

The regulation of exciton properties plays a crucial role in enhancing the activity of photocatalysts, primarily due to the rapid recombination of photoinduced electron-hole pairs caused by the strong Coulomb interaction between them. In this study, we explore the spin polarization effect in nanohybrids composed of graphitic carbon nitride (g-C₃N₄) and iron (Fe) nanoparticles, which accelerates exciton dissociation and spin-selective electron transfer, thereby improving the selective photoreduction of CO₂ into CO. Mechanistic studies reveal that the Fe²⁺/Fe³⁺ redox pairs, embedded in the iron oxide layer on the surface of Fe nanoparticles, function as ultrafast charge transfer shuttles via a double exchange interaction (Fe²⁺─O─Fe³⁺). This process facilitates spin-selective electron transfer from g-C₃N₄ to Fe species, thereby contributing to the efficient conversion of CO₂. This work provides novel insights into the design of spin-dependent photocatalysts for efficient solar energy conversion.