Type-I CdS/ZnS Core/Shell Quantum Dot-Gold Heterostructural Nanocrystals for Enhanced Photocatalytic Hydrogen Generation

Abstract

Developing Type-I core/shell quantum dots is of great importance toward fabricating stable and sustainable photocatalysts. However, the application of Type-I systems has been limited due to the strongly confined photogenerated charges by the energy barrier originating from the wide-bandgap shell material. In this project, we found that through the decoration of Au satellite-type domains on the surface of Type-I CdS/ZnS core/shell quantum dots, such an energy barrier can be effectively overcome and an over 400-fold enhancement of photocatalytic H2 evolution rate was achieved compared to bare CdS/ZnS quantum dots. Transient absorption spectroscopic studies indicated that the charges can be effectively extracted and subsequently transferred to surrounding molecular substrates in a subpicosecond time scale in such hybrid nanocrystals. Based on density functional theory calculations, the ultrafast charge separation rates were ascribed to the formation of intermediate Au2S layer at the semiconductor–metal interface, which can successfully offset the energy confinement introduced by the ZnS shell. Our findings not only provide insightful understandings on charge carrier dynamics in semiconductor–metal heterostructural materials but also pave the way for the future design of quantum dot-based hybrid photocatalytic systems.

Ni2P Anchored on Barbituric Acid-Modified Graphitic Carbon Nitride as a Versatile Photocatalyst for Hydroxylation of Aryl Boronic Acids and Oxidation of Benzyl Alcohols

“…73−75 The interplay between interfacial electric fields and the conductivity of interfacial layers can significantly influence electron−hole dynamics, thereby impacting photocatalytic performance. 69,73 The observed band features of constituting ba-g-C 3 N 4 and MOFderived Ni 2 P (which inevitably has a carbon layer, as evidenced by Figure S8) strictly justify their choice to be employed for the formation of composite photocatalysts for effecting the targeted organic transformations. With the present band setting, the composite photocatalyst well fits the bill for suitable aerobic oxidation reactions given the fact that the band potential of −0.38 eV vs NHE (CB of Ni 2 P) can easily generate O 2 −• radicals (redox potential of −0.33 eV vs NHE) that can initiate a good number of organic transformations.…”

“…The observed potentials in the individual components perfectly fit in the straddling type-1 band alignment, an arrangement well appreciated for photoemission and anticipated to have limited efficiency for photocatalysis. However, with the slight interfacial modifications targeted toward the mitigation of charge recombination, the type-I band alignment has been seen to deliver exceptional photocatalytic performance. − The interplay between interfacial electric fields and the conductivity of interfacial layers can significantly influence electron–hole dynamics, thereby impacting photocatalytic performance. , The observed band features of constituting ba-g-C 3 N 4 and MOF-derived Ni 2 P (which inevitably has a carbon layer, as evidenced by Figure S8) strictly justify their choice to be employed for the formation of composite photocatalysts for effecting the targeted organic transformations. With the present band setting, the composite photocatalyst well fits the bill for suitable aerobic oxidation reactions given the fact that the band potential of −0.38 eV vs NHE (CB of Ni 2 P) can easily generate O 2 –• radicals (redox potential of −0.33 eV vs NHE) that can initiate a good number of organic transformations .…”

Interfacial Chemical-Bonded MoS2/In–Bi2MoO6 Heterostructure for Enhanced Photocatalytic Nitrogen-to-Ammonia Conversion

“…According to the band-energy calculation demonstrated, the effective masses of electrons ( m e *) for MoS 2 (0.533) were much smaller than that of BMO (1.583), while the effective masses of holes ( m h *) for BMO (−0.641) were close to MoS 2 (−0.640), indicating higher charge carrier mobilities post formation of Mo–S interfacial chemical-bond (Table S4). In other words, under illumination, the photogenerated e – /h + will accumulate on MoS 2 and BMO, respectively. The DFT estimation agreed with the photoelectrochemical and photocatalytic results.…”

Recent progress on the photocatalytic hydrogen evolution reaction over a metal sulfide cocatalyst-mediated carbon nitride system

“…), 11,12 metal sulfides (CdS, ZnS, etc . ), 13,14 noble metal semiconductors (AgBr, Ag 3 PO 4 , etc . ), 15,16 semiconducting polymers (polypyrrole, polydopamine, etc .…”