Dual-Site Cooperativity in Ag/Cu-Ag₂S Cocatalyst for CO₂ Activation and Deep Hydrogenation Towards 100%-Selective CH₄ Photoproduction

The photocatalytic reduction of CO₂ to CH₄ is essential for carbon neutrality but remains challenging due to the high stability of CO₂ and the complex multi‑electron pathway, typically leading to CO as the dominant product with low CH₄ selectivity. Herein, a bifunctional Ag‑loaded, Cu‑doped Ag₂S (ACAS) hollow‑sphere cocatalyst is fabricated on ZnIn₂S₄ (ZIS) nanoflowers via a self‑templated ion‑exchange strategy. Under simulated sunlight, ACAS/ZIS achieves an outstanding CH₄ evolution rate of 145.2 µmol·g⁻¹·h⁻¹ with 100% selectivity. This performance stems from a unique “light‑electricity‑heat” synergy: the intrinsic dipole field in ZIS drives directional electron migration to ACAS, while the full‑spectrum absorption of ACAS induces a localized photothermal effect that supplies energy for C─O bond cleavage. In-situ spectroscopy and theoretical calculations reveal that Cu sites dominate CO₂ adsorption and lower the energy barrier for *COOH formation. Concurrently, in-situ generated metallic Ag nanoparticles cooperate with Cu sites to create a dual‑active‑site interface, activating *CO and dramatically reducing the rate‑determining barrier for its hydrogenation to *CHO. This work establishes a catalyst design paradigm that integrates localized photothermal heating with atomically engineered bifunctional sites to drive the highly selective deep reduction of CO₂ to CH₄.