Strain‐Tuned d‐Band Center Coupling Dual‐Plasmon Effect in CuIn Alloy for Driving CO 2 Photoreduction

into liquid fuels. However, the limitations of traditional plasmonic catalysts result in low catalytic efficiency. Here, an indium (In) atomic layer has been developed as a new plasmonic material, while Cu is incorporated into the In lattice to form a CuIn alloy, yielding a dual-plasmonic photocatalyst. The alloying of Cu and In induces significant lattice compression strain and shortens interatomic electron transfer distance. This electron redistribution endows the Cu-In site pairs with an electron-rich structure and modulates the d-band center to optimize adsorption capacity. This dual-plasmon effect strengthens electron-phonon coupling and optimizes the thermodynamics of surface reactions, enabling CuIn to maintain high activity and stability. This work provides a new design strategy for the development of strain-tuned dual-plasmon materials.