Ultrafast Charge Separation for Full Solar Spectrum-Activated Photocatalytic H₂ Generation in a Black Phosphorus–Au–CdS Heterostructure

Abstract

Two-dimensional layered black phosphorus (BP) with a tunable band gap of 0.3–2.0 eV has received great interest in broad-spectrum-active photocatalysis, but rapid charge recombination limits its potential applications. Herein, we report that BP quantum dots (QDs) work as active photosensitizer in a ternary heterostructure consisting of BP QDs, Au nanorods (NRs), and CdS nanowires (NWs), which efficiently photocatalytically generates H2 at full solar spectrum, especially in the near-infrared (NIR) region. The superior performance of the BP–Au–CdS heterostructure arises from the overall photoabsorption contribution, the dual role (electron relay and plasmonic electron donor) of Au NRs, as well as the appropriate band alignment and strong coupling between the three components. Tracking the electron and hole transfers via femtosecond transient absorption spectroscopy shows a unidirectional electron flow from BP to Au and then to CdS, which has been achieved by the high conduction band level of BP, the well-harnessed work function match in BP–Au, and the well-established Schottky barrier in Au–CdS heterojunction.

Near‐Infrared‐Driven Photocatalysts: Design, Construction, and Applications

“…Black phosphorus [90] 0.3 (monolayer) -2.0 (bulk) Ag 2 O [24] 1. [65] This article is protected by copyright.…”

“…Interestingly, the chalcogenides account for a large proportion of narrow band-gap semiconductors, which is mainly originated from the dispersive band structure of chalcogenides contributed by d orbital of the metal and p orbital of chalcogen. [94] For traditional narrow band-gap semiconductors including Bi 2 S 3 , [89] Ag 2 S [88] and black phosphorus, [90] their recombination of charge carriers is usually fast. In addition, the band position of these narrow bandgap semiconductors is hard to match with the oxidation/reduction potentials of the photocatalytic reaction, which inhibits their redox ability.…”

Enriching Hot Electrons via NIR‐Photon‐Excited Plasmon in WS2@Cu Hybrids for Full‐Spectrum Solar Hydrogen Evolution

“…Many studies have focused on expanding the response range of semiconductor photocatalysts to the solar light spectrum for the enhanced STH efficiency . However, the near‐infrared (NIR) light that contains approximately 45% of solar light energy becomes an awkward portion because its photonic energy may be too low to meet directly the basic thermodynamics of water redox reaction . Thus how to open a window of the NIR light is one of valuable challenges for solar water splitting …”

A Low‐Cost Metal‐Free Photocatalyst Based on Black Phosphorus

“…[14] Furthermore, because of the 2D structure, BP shows a high charge mobility up to 1000 cm 2 V −1 s −1 and large surface area. Consequently, various BP-based heterostructures such as BP/TiO 2 , [22] BP/CoP, [23] BP/Au/La 2 Ti 2 O 7 , [24] BP/BiVO 4 , [25] and BP/Au/CdS [26] have been proposed to have good photocatalytic characteristics. Consequently, various BP-based heterostructures such as BP/TiO 2 , [22] BP/CoP, [23] BP/Au/La 2 Ti 2 O 7 , [24] BP/BiVO 4 , [25] and BP/Au/CdS [26] have been proposed to have good photocatalytic characteristics.…”