Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution

A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (lambda > 420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs.