A cocatalyst-free Eosin Y-sensitized p-type of Co<sub>3</sub>O<sub>4</sub> quantum dot for highly efficient and stable visible-light-driven water reduction and hydrogen production

Zhang, Ning; Shi, Jinwen; Niu, Fujun; Wang, Jian; Guo, Liejin

doi:10.1039/c5cp02983j

Cited by 44 publications

(16 citation statements)

References 19 publications

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“…1b, CdS exhibits a broad emission centered at 545 nm, which is attributed to the irradiative bandtransition recombination of photogenerated electrons and holes. [36] When Co was added, the band-transition emission of CdS was quenched dramatically and slightly redshifted from 545 nm to 550 nm, which is likely due to the close interaction between Co and CdS, [37][38][39] Co adsorption, which is in good agreement with the PL results.…”

Section: Interaction Between Cds and Co Coenzymesupporting

confidence: 64%

Cobaloxime coenzyme catalyzing artificial photosynthesis for hydrogen generation over CdS nanocrystals

Niu

Shen

Zhang

et al. 2016

Applied Catalysis B: Environmental

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Section: Interaction Between Cds and Co Coenzymesupporting

confidence: 64%

Cobaloxime coenzyme catalyzing artificial photosynthesis for hydrogen generation over CdS nanocrystals

Niu

Shen

Zhang

et al. 2016

Applied Catalysis B: Environmental

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“…It is noted that the work function is closer to the VBM of WSe 2 (−5.35 eV), which indicates that the pristine WSe 2 has inherent p‐type characteristics. The flat band potential of the EY layer is ≈−5.04 eV . In EY‐WSe 2 heterolayers, electron transfer will take place from WSe 2 to low‐lying EY to compensate the energy level difference, and their work function should be between the levels of WSe 2 and EY.…”

Section: Results and Disccussionmentioning

confidence: 99%

“…EY's lowest unoccupied molecular orbital (LUMO) level is positioned lower than the CBM of 6L WSe 2 , and its highest occupied molecular orbital (HOMO) level is lower than the VBM of 1L WSe 2 , forming a type II alignment . Additionally, EY is a water‐soluble dye molecule and can provide a p‐doping on WSe 2 . In a previous report, we found that not only organic dopants, but also solvents where dopant molecules are dispersed can contribute to interlayer charge transfer to/from 2D TMDC layers, depending on the relative electronegativity .…”

Section: Introductionmentioning

confidence: 99%

Layer‐Number‐Dependent Electronic and Optoelectronic Properties of 2D WSe₂‐Organic Hybrid Heterojunction

Choi

2019

Adv Materials Inter

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One of the most attractive features of 2D WSe2 is a tunability in its electronic and optoelectronic properties depending on the layer number. To harness such unique characteristics for device applications, high quality and easily processable heterojunctions are required and relevant layer‐number‐dependent properties must be understood. Herein, a study is reported on hybrid heterojunctions between 2D WSe2 and organic molecules from one‐step solution chemistry and their layer‐number‐dependent properties. Eosin Y (EY) dye is selected as a p‐dopant and uniformly stacked on mechanically exfoliated WSe2 flakes via van der Waals interaction, forming a hybrid heterojunction with a type II alignment. The EY‐WSe2 heterojunction shows significantly enhanced currents compared to pristine WSe2 with a lower barrier height and a longer effective screening length. The work function of the heterostructure is also lower than that of pristine WSe2. The efficient exciton dissociation and doping effect by EY are confirmed by photocurrent and photoluminescence measurements, where WSe2 emission is markedly quenched by EY and exciton contribution decreases with layer number. These findings shed critical insights into layer‐number‐dependent electronic and optoelectronic properties of organic‐WSe2 layers and also provide simple yet effective means to construct transition metal dichalcogenide‐based heterostructures, which should be valuable for developing layered 2D devices.

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“…ii) The excited electrons at TiO 2 may suppress to transfer to CFCO by widening of bandgap energy of CFCO by decreasing of particle size to 5 nm, i.e., quantum confinement effect. Some researchers reported that bandgap energies of simple oxides such as Co 3 O 4 [ 38,39 ] and Fe 2 O 3 [ 40 ] became larger with decreasing the particle size to 3–4 nm. In our case (Figure S8, Supporting Information), CFCO/TiO 2 prepared by the RM method with R w = 3 showed specific visible light absorption at less than 900 nm (the sample color is yellowish), even though the electrons and holes excited by such visible light were not used to oxygen photoevolution reaction (Figure S9, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Brownmillerite‐Type Crystalline Ca₂FeCoO₅ Ultrasmall Particles with Single‐Nanometer Dimensions as an Active Cocatalyst for Oxygen Photoevolution Reaction

Tsuji

Nanbu

Degami

et al. 2020

Part & Part Syst Charact

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transfer processes. [2,3] For highly efficient water splitting method, we believe it is quite important to find an effective photocatalyst for OER. Many researchers have attempted to improve photocatalytic activity by loading cocatalysts, which are active for the OER step on photocatalysts or semiconductors. [1][2][3] Although noble metal oxides such as RuO 2 [4,5] and IrO 2 [6] show higher catalytic activity for OER and have also been used as cocatalysts of photocatalysts, the lack of sufficient reserves prohibits their large-scale uses. Therefore, it is necessary to find a promising OER cocatalyst consisting of only transition metal elements. Among transition metal cocatalysts, cobalt-containing materials, such as cobalt oxides (CoO x ) [8][9][10] and cobalt phosphate (Co-Pi), [11,12] are ones of the most frequently studied as the OER cocatalysts, whereas their OER activity are not higher than those of the noble metal oxides. Recently we found that brownmillerite (BM)-type Ca 2 FeCoO 5 (CFCO) possessed higher catalytic OER activity than the noble metal oxides in an alkaline solution. [13,14] The BM structure is categorized as an oxygen-deficiencyordered perovskite-type structure containing a layered arrangement of octahedral (Oh) BO 6 and tetrahedral (Td) BO 4 . [15][16][17][18] Such Oh-and Td-sites are likely to play distinct roles in the enhanced OER activity: the former mainly decreases the overpotential, and the latter enhances the OER current. [13] Therefore, BM-type CFCO is expected to act as a new active cocatalyst for OER by combination with photocatalysts.In general, the particle size of cocatalyst is several nanometers due to increasing interface between the parent catalyst and the cocatalyst, and exposure of the active sites. [4][5][6][7][8][9][10][11][12] For example, Liu et al. reported size influence of metal oxide cocatalysts on photocatalytic activity of TiO 2 nanosheets for OER. [19] Charge-transfer process in TiO 2 was significantly accelerated by loading the metal oxides clusters with ≈2 nm diameter, leading to enhance the photocatalytic water oxidation rate to oxygen. In solutions, on the other hand, nanometric oxide particles have been utilized as the OER cocatalysts. [20][21][22][23] For example, Maeda and co-workers reported OER catalytic activity of Fe(III)-Cr(III) oxide solid solution [20] combined with PdCrO x[21] on SrTiO 3Brownmillerite-type Ca 2 FeCoO 5 (CFCO) is one of the most effective catalysts for oxygen evolution reaction (OER), comparable with noble metal oxides. In this study, crystalline CFCO ultrasmall particles with nanometric dimension are synthesized by a reverse micelle method on TiO 2 nanoparticles. The particle size decreases with decreasing molar ratio of water to surfactant. The precursors of CFCO must be calcined after loading on TiO 2 nanoparticles to achieve CFCO ultrasmall particles with several nanometers in size. Interaction between the precursors and TiO 2 is speculated to suppress aggregation of the precursors during calcination. The photocatalytic activity...

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A cocatalyst-free Eosin Y-sensitized p-type of Co₃O₄ quantum dot for highly efficient and stable visible-light-driven water reduction and hydrogen production

Abstract: Owing to the effect of energy band bending, p-type Co3O4 quantum dots sensitized by Eosin Y showed a high and stable photocatalytic activity (∼13,440 μmol h(-1) g(-1)(cat)) for water reduction and hydrogen production under visible-light irradiation without any cocatalyst.

Cited by 44 publications

References 19 publications

Cobaloxime coenzyme catalyzing artificial photosynthesis for hydrogen generation over CdS nanocrystals

Cobaloxime coenzyme catalyzing artificial photosynthesis for hydrogen generation over CdS nanocrystals

Layer‐Number‐Dependent Electronic and Optoelectronic Properties of 2D WSe₂‐Organic Hybrid Heterojunction

Brownmillerite‐Type Crystalline Ca₂FeCoO₅ Ultrasmall Particles with Single‐Nanometer Dimensions as an Active Cocatalyst for Oxygen Photoevolution Reaction

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A cocatalyst-free Eosin Y-sensitized p-type of Co3O4 quantum dot for highly efficient and stable visible-light-driven water reduction and hydrogen production

Abstract: Owing to the effect of energy band bending, p-type Co3O4 quantum dots sensitized by Eosin Y showed a high and stable photocatalytic activity (∼13,440 μmol h(-1) g(-1)(cat)) for water reduction and hydrogen production under visible-light irradiation without any cocatalyst.

Cited by 44 publications

References 19 publications

Cobaloxime coenzyme catalyzing artificial photosynthesis for hydrogen generation over CdS nanocrystals

Cobaloxime coenzyme catalyzing artificial photosynthesis for hydrogen generation over CdS nanocrystals

Layer‐Number‐Dependent Electronic and Optoelectronic Properties of 2D WSe2‐Organic Hybrid Heterojunction

Brownmillerite‐Type Crystalline Ca2FeCoO5 Ultrasmall Particles with Single‐Nanometer Dimensions as an Active Cocatalyst for Oxygen Photoevolution Reaction

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A cocatalyst-free Eosin Y-sensitized p-type of Co₃O₄ quantum dot for highly efficient and stable visible-light-driven water reduction and hydrogen production

Layer‐Number‐Dependent Electronic and Optoelectronic Properties of 2D WSe₂‐Organic Hybrid Heterojunction

Brownmillerite‐Type Crystalline Ca₂FeCoO₅ Ultrasmall Particles with Single‐Nanometer Dimensions as an Active Cocatalyst for Oxygen Photoevolution Reaction