IR-Driven Ultrafast Transfer of Plasmonic Hot Electrons in Nonmetallic Branched Heterostructures for Enhanced H₂ Generation.

Abstract

The ultrafast transfer of plasmon-induced hot electrons is considered an effective kinetics process to enhance the photoconversion efficiencies of semiconductors through strong localized surface plasmon resonance (LSPR) of plasmonic nanostructures. Although this classical sensitization approach is widely used in noble-metal-semiconductor systems, it remains unclear in nonmetallic plasmonic heterostructures. Here, by combining ultrafast transient absorption spectroscopy with theoretical simulations, IR-driven transfer of plasmon-induced hot electron in a nonmetallic branched heterostructure is demonstrated, which is fabricated through solvothermal growth of plasmonic W₁₈ O₄₉ nanowires (as branches) onto TiO₂ electrospun nanofibers (as backbones). The ultrafast transfer of hot electron from the W₁₈ O₄₉ branches to the TiO₂ backbones occurs within a timeframe on the order of 200 fs with very large rate constants ranging from 3.8 × 10¹² to 5.5 × 10¹² s^-1 . Upon LSPR excitation by low-energy IR photons, the W₁₈ O₄₉ /TiO₂ branched heterostructure exhibits obviously enhanced catalytic H₂ generation from ammonia borane compared with that of W₁₈ O₄₉ nanowires. Further investigations by finely controlling experimental conditions unambiguously confirm that this plasmon-enhanced catalytic activity arises from the transfer of hot electron rather than from the photothermal effect.