Single-Atom Pt Anchored Polyoxometalate as Electron-Proton Shuttle for Efficient Photoreduction of CO2 to CH4 Catalyzed by NiCo Layered Doubled Hydroxide

Abstract

The crucial role of active hydrogen (H*) in photocatalytic CO₂ methanation has long been overlooked, although recently, accelerating proton-coupled electron transfer (PCET) processes to enhance CH₄ productivity and selectivity has garnered significant attention. Herein, a single-atom Pt-anchored H₃PMo₁₂O₄₀ (Pt₁-PMo₁₂) is applied as an efficient proton–electron shuttle to facilitate the photocatalytic performance of NiCo layered double hydroxide (NiCo-LDH). The resultant Pt₁-PMo₁₂@NiCo-LDH exhibited superior CH₄ productivity (723 µmol g⁻¹ h⁻¹) with CH₄ selectivity of 82.3%, showcasing a 24.9 times productivity enhancement over NiCo-LDH (29 µmol g⁻¹ h⁻¹). Systematic investigations revealed that abundant H* is generated by the dissociation of H₂O on Pt₁ sites and stored within Pt₁-PMo₁₂. Subsequently, the multiple H* rapidly migrated from Pt₁-PMo₁₂ to the catalytic sites on NiCo-LDH by the engineered strong Mo─O─Ni/Co bonds, thereby significantly expediting the PCET process. The in situ DRIFTS and theoretical calculations elucidated that the Pt₁-PMo₁₂ decreased the energy barrier for *CO protonation to *CHO (0.38–0.18 eV) and optimized the rate-determining step of *CH₃ to *CH₄ (0.64 eV), thus promoting highly active and selective CH₄ generation. This work provided novel insights into achieving efficient photocatalytic CO₂ methanation by modulating the fast generation and transport of active H*.