Exceptional Catalytic Nature of Quantum Dots for Photocatalytic Hydrogen Evolution without External Cocatalysts

Abstract

The catalytic nature of semiconducting quantum dots (QDs) for photocatalytic hydrogen (H2) evolution can be thoroughly aroused, not because of coupling with external cocatalysts, but through partially covering controlled amount of ZnS shell on the surface. Specifically, CdSe QDs, with an optimal coverage of ZnS (≈46%), can produce H2 gas with a constant rate of ≈306.3 ± 21.1 µmol mg−1 h−1 during 40 h, thereby giving a turnover number of ≈(4.4 ± 0.3) × 105, which is ≈110‐fold to that of unmodified CdSe QDs under identical conditions. The performance of H2 evolution is comparable to or even better than the commonly used external cocatalysts, e.g., metal complexes, noble metals assisted photosystems. Mechanistic insights indicate that the dramatically enhanced activity and stability of bare QDs for photocatalytic H2 production are derived from (i) inhibiting exciton annihilation at trap states, (ii) preventing the photo‐oxidation of core frameworks, and (iii) retaining tunneling efficiencies of photogenerated electrons and holes to reactive sites with partial ZnS coverage.

Interface engineering of InP/ZnS core/shell quantum dots by the buffer monolayer for exceptional photocatalytic H 2 evolution

“…S8 †), this is probably because shells with excessive thickness inhibit the excitons transfer from the InP core to the QD surface in type-I heterostructures, which has been proved in the case of CdSe/ZnS core/shell QDs in our recent work. 30 The InP/ZnS QDs synthesized using S-TOP without the S x -In-P 1−x buffer layer (Fig. S9 †) exhibit a similar trend of change for H 2 evolution with the increase of thickness (Fig.…”

“…The lattice mismatch of S x -In-P 1−x with InP is smaller than that of ZnS, therefore the formation of the buffer layer would also decline the interface defects between the core and shell. 28 On the other hand, different from the typical type-I heterostructure in which the shell would block the photogenerated charge transfer to the surface and decrease their photocurrent density, 30,45 here the formed alloyed interface of S x -In-P 1−x would spread the radial probability density of electrons and holes in the buffer layer, which enables the photogenerated excitons to tunnel out of the surface of QDs. [46][47][48] Therefore, the delocalization of photogenerated excitons would help realize the spatial separation of electrons and holes, increasing the probability of excitons tunnelling out of the QDs and the corresponding redox reactions.…”

Enhanced Photocatalytic Charge Separation in Coating‐Protected Porous Silicon Quantum Dot Films With Stability Approaching 100 Hours

“…The entire assembly is immersed in a 100 mM FeCl 2 aqueous solution and illuminated with a 1000 W Xe lamp equipped with a 400 ± 10 nm bandpass filter. Based on the demonstrated HER activity shown in Figure 5 (fitted to be 0.58 µmol cm -2 h -1 ) and the absorption spectrum (Figure S6b), the IQE in the wavelength range of 400 ± 10 nm is calculated to be 14.1 %, which is comparable to or even better than other non-Si systems [39][40][41][42][43][44][45] summarized in Table S1, demonstrating the superiority of this work.…”

Controlled Photoinduced Electron Transfer from InP/ZnS Quantum Dots through Cu Doping: A New Prototype for the Visible-Light Photocatalytic Hydrogen Evolution Reaction

“…For demonstration that the present Cu doped InP/ZnS QDs are promising candidates for high-performance photocatalysts, the photocatalytic H 2 evolution activity of the InP/Cu:3ZnS QDs obtained for irradiation time of 40 h was extensively compared with those of recently reported QD catalysts (Table S3). ,− Apparently, the InP/Cu:3ZnS QDs exhibited superior H 2 evolution performance over those of the QD photocatalysts previously reported (Table S3). Powder X-ray diffraction (XRD) and XPS data confirmed that the zincblende structure and chemical states of the InP/Cu:4ZnS QDs were preserved after stability tests (Figure S13).…”