Plasmonic Active "Hot Spots"-Confined Photocatalytic CO₂ Reduction with High Selectivity for CH₄ Production

Plasmonic nanostructures have tremendous potential to be applied in photocatalytic CO₂ reduction, since their localized surface plasmon resonance can collect low-energy-photons to derive energetic "hot electrons" for reducing the CO₂ activation-barrier. However, the hot electron-driven CO₂ reduction is usually limited by poor efficiency and low selectivity for producing kinetically unfavorable hydrocarbons. Here, a new idea of plasmonic active "hot spot"-confined photocatalysis is proposed to overcome this drawback. W₁₈ O₄₉ nanowires on the outer surface of Au nanoparticles-embedded TiO₂ electrospun nanofibers are assembled to obtain lots of Au/TiO₂ /W₁₈ O₄₉ sandwich-like substructures in the formed plasmonic heterostructure. The short distance (< 10 nm) between Au and adjacent W₁₈ O₄₉ can induce an intense plasmon-coupling to form the active "hot spots" in the substructures. These active "hot spots" are capable of not only gathering the incident light to enhance "hot electrons" generation and migration, but also capturing protons and CO through the dual-hetero-active-sites (Au-O-Ti and W-O-Ti) at the Au/TiO₂ /W₁₈ O₄₉ interface, as evidenced by systematic experiments and simulation analyses. Thus, during photocatalytic CO₂ reduction at 43± 2 °C, these active "hot spots" enriched in the well-designed Au/TiO₂ /W₁₈ O₄₉ plasmonic heterostructure can synergistically confine the hot-electron, proton, and CO intermediates for resulting in the CH₄ and CO production-rates at ≈35.55 and ≈2.57 µmol g^-1 h^-1 , respectively, and the CH₄ -product selectivity at ≈93.3%.