Unexpected Negative-Ion Conversion in Grazing Scattering of Negative Ions on HOPG

Guo, Xinyue; Liu, Pinyang; Ding, Bin; Zhang, Luyao; Wang, Jiawei; Guo, Yue; Zhong, Guang; Li, Xuan; Wang, Lei; Wei, Mingxuan; Guo, Yanling; Chen, Lin; Chen, Ximeng

doi:10.1021/acs.jpcc.1c01609

Cited by 9 publications

(6 citation statements)

References 79 publications

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“…By comparing the steady state absorption and TA spectra (Figure S7, Supporting Information), the PIB at ≈700 nm was attributed to the state‐filling effect under excitation. [ 20,60–62 ] PIA1 and PIA2 was assigned to the photoinduced free carrier absorption in the conduction band corresponding to the 3d state of Co 2+ and Co 3+ , respectively. [ 26,63–66 ] As shown in Figure 4c, PIB signal was appeared later than the signal of PIA1 and PIA2.…”

Section: Resultsmentioning

confidence: 99%

Unveiling the Origin of Co₃O₄Quantum Dots for Photocatalytic Overall Water Splitting

Guo

Liu

Wang

et al. 2023

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Previous studies reveal that oxygen evolution reaction is the bottleneck in overall water splitting process because of the four electron redox reaction. [8][9][10][11][12] Co 3 O 4 , as a p-type semiconductor with a band gap of ≈2.1 eV, has been demonstrated as a good candidate for photocatalytic water oxidation due to the environmental friendliness, visible light response, and superior oxidation ability. [13][14][15][16][17] Unfortunately, photocatalytic water reduction to hydrogen is difficult to proceed over Co 3 O 4 nanocrystal, because the conduction band edge was more positive than H 2 evolution potential (0 eV versus NHE). Proper design and modification of conduction band edge position are desired for hydrogen evolution over Co 3 O 4 semiconductors. For example, F-doped Co 3 O 4 were prepared via a plasma assisted method and showed photocatalytic hydrogen generation from water/ethanol solution. [18] Recently, quantum semiconductors have emerged as efficient photocatalysts owing to high specific area, short charge transfer distance, and superior light absorption. [19][20][21] Particularly, the band gaps will be enlarged and the conduction band edge will be elevated when the crystal size of prepared photocatalysts was reduced to smaller than its Bohr radius. [22][23][24] Thus, overall water splitting to hydrogen and oxygen is expected over Co 3 O 4 QDs. For example, Zhang et al. adopt a reverse micelle method to prepare Co 3 O 4 QDs and it showed pure water splitting. [22] In addition, photo-induced charge transfer and separation plays an important role in determining the photocatalyst efficiency. However, poor studies of charge transfer were conducted on Co 3 O 4 QDs owing to their complicated electronic structure and ionic bonding character. [25,26] Efficient hole injection from sensitizer p-oligo (phenylenevinylene) molecular to Co 3 O 4 was observed through transient optical absorption spectroscopy study. [27] Owing to the weak coupled, localized d state, long lived charge carrier of d-d excitations was characterized in Co 3 O 4 . [28] In order to propel the wide application of Co 3 O 4 based photocatalysts, solid understanding of charge carrier dynamic in Co 3 O 4 is urgently required.Herein, we adopt a solvothermal method to prepare colloidal Co 3 O 4 quantum dots, and applied transient absorption (TA) spectroscopy to study the charge carrier dynamics of Co 3 O 4 QDs during the water splitting process. The obtained Co 3 O 4 QDs displayed overall water splitting to hydrogen and oxygen without cocatalysts loading. TA spectroscopy results suggested that charge transfer from 2p state of O 2p to 3d state of Co 2+ played

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Section: Resultsmentioning

confidence: 99%

Unveiling the Origin of Co₃O₄Quantum Dots for Photocatalytic Overall Water Splitting

Guo

Liu

Wang

et al. 2023

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“…Loading Ni‐based cocatalysts decreased the PL signals of HRP and RP. The stronger quenching effect in Ni‐HRP compared to that in Ni−RP indicated the role of the Ni single‐atom sites in suppressing the radiative electron‐hole recombination (Figure 6a) [26] . The increased surface photovoltage (SPV) intensity of Ni‐HRP confirmed the efficient separation of photogenerated electron‐hole pairs (Figure 6b), [27] which was further supported by the electrochemical impedance spectroscopy (EIS) analysis (Figure 6c and Table S3).…”

Section: Resultsmentioning

confidence: 99%

Atomically Dispersed Janus Nickel Sites on Red Phosphorus for Photocatalytic Overall Water Splitting

Burda

Wang

et al. 2022

Angew Chem Int Ed

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Single-atom nickel catalysts hold great promise for photocatalytic water splitting due to their plentiful active sites and cost-effectiveness. Herein, we adopt a reactive-group guided strategy to prepare atomically dispersed nickel catalysts on red phosphorus. The hydrothermal treatment of red phosphorus leads to the formation of PÀ H and PÀ OH groups, which behave as the reactive functionalities to generate the dual structure of single-atom PÀ Ni and PÀ OÀ Ni catalytic sites. The produced single-atom sites provide two different functions: PÀ Ni for water reduction and PÀ OÀ Ni for water oxidation. Benefitting from this specific Janus structure, Ni-red phosphorus shows an elevated hydrogen evolution rate compared to Ni nanoparticle-modified red phosphorus under visible-light irradiation. The hydrogen evolution rate was additionally enhanced with increased reaction temperature, reaching 91.51 μmol h À 1 at 70 °C, corresponding to an apparent quantum efficiency of 8.9 % at 420 nm excitation wavelength.

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“…Kubelka‐Munk method was applied to determine the accurate band gaps of studied catalysts and Tauc plots of ( F ⋅ hν ) 2 versus hν are shown in Figure 7b. F was calculated according to the Kubelka‐Munk formula ( F =(1− R ) 2 /2 R ), where R is the relative diffuse reflectance determined by the formula of R =1/10 α ; α is the absorption coefficient [5c,25b] . The estimated values of direct band‐gaps for ZnO, ZnO/ZnS, ZnO/ZnS/CdS‐1, ZnO/ZnS/CdS‐2, ZnO/ZnS/CdS‐3 and ZnO/CdS were 3.14, 3.13, 2.62, 2.58, 2.55, and 2.29 eV, respectively, suggesting that the band‐gaps of heterostructures were successfully adjusted by varying the components and synthesis strategy.…”

Section: Resultsmentioning

confidence: 99%

Heterointerface Engineering of ZnO/CdS Heterostructures through ZnS Layers for Photocatalytic Water Splitting

Guo

Liu

Yan

et al. 2022

Chemistry A European J

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Solar-driven water splitting to produce clean and renewable hydrogen offers a green strategy to address the energy crisis and environmental pollution. Heterostructure catalysts are receiving increasing attention for photocatalytic hydrogen generation. ZnO/ZnS/CdS and ZnO/CdS heterostructures have been successfully designed and prepared according to two different strategies. By introducing a heterointerface layer of ZnS between ZnO and CdS, a Z scheme charge-transfer channel was promoted and achieved superior photocatalytic performance. A highest hydrogen generation rate of 156.7 μmol g À 1 h À 1 was achieved by precise control of the thickness of the heterointerface layer and of the CdS shell. These findings demonstrated that heterostructures are promising catalysts for solar-driven water splitting, and that heterointerface engineering is an effective way to improve the photocatalytic properties of heterostructures.

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Unexpected Negative-Ion Conversion in Grazing Scattering of Negative Ions on HOPG

Cited by 9 publications

References 79 publications

Unveiling the Origin of Co₃O₄Quantum Dots for Photocatalytic Overall Water Splitting

Unveiling the Origin of Co₃O₄Quantum Dots for Photocatalytic Overall Water Splitting

Atomically Dispersed Janus Nickel Sites on Red Phosphorus for Photocatalytic Overall Water Splitting

Heterointerface Engineering of ZnO/CdS Heterostructures through ZnS Layers for Photocatalytic Water Splitting

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Unexpected Negative-Ion Conversion in Grazing Scattering of Negative Ions on HOPG

Cited by 9 publications

References 79 publications

Unveiling the Origin of Co3O4Quantum Dots for Photocatalytic Overall Water Splitting

Unveiling the Origin of Co3O4Quantum Dots for Photocatalytic Overall Water Splitting

Atomically Dispersed Janus Nickel Sites on Red Phosphorus for Photocatalytic Overall Water Splitting

Heterointerface Engineering of ZnO/CdS Heterostructures through ZnS Layers for Photocatalytic Water Splitting

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Unveiling the Origin of Co₃O₄Quantum Dots for Photocatalytic Overall Water Splitting

Unveiling the Origin of Co₃O₄Quantum Dots for Photocatalytic Overall Water Splitting