Dual‐Site Cooperativity in Ag/Cu‐Ag ₂ S Cocatalyst for CO ₂ Activation and Deep Hydrogenation Towards 100%‐Selective CH ₄ Photoproduction

ABSTRACT The photocatalytic reduction of CO ₂ to CH ₄ is essential for carbon neutrality but remains challenging due to the high stability of CO ₂ and the complex multi‑electron pathway, typically leading to CO as the dominant product with low CH ₄ selectivity. Herein, a bifunctional Ag‑loaded, Cu‑doped Ag ₂ S (ACAS) hollow‑sphere cocatalyst is fabricated on ZnIn ₂ S ₄ (ZIS) nanoflowers via a self‑templated ion‑exchange strategy. Under simulated sunlight, ACAS/ZIS achieves an outstanding CH ₄ 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 CO ₂ 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 CO ₂ to CH ₄ .