Janus‐Structured Co‐Ti<sub>3</sub>C<sub>2</sub> MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

Tang, Rui; Zhou, Shujie; Li, Caixia; Chen, Ran; Zhang, Luyuan; Zhang, Zhiwei; Yin, Longwei

doi:10.1002/adfm.202000637

Cited by 116 publications

(82 citation statements)

References 54 publications

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“…[ 137 ] The decrease in the spatial overlap between electron and hole wave functions could reduce their Coulomb interaction and increases the lifetimes of single and multiple exciton states, [ 136 ] delaying the charge recombination process [ 135 ] and resulting in an enhanced electron transfer rate. These observations identify that Type‐II and Quasi‐Type‐II core/shell nano‐heterostructured QDs are suitable for PEC systems in terms of charge transfer behavior, samples including CdTe/CdS QDs, [ 138 ] CdSe/CdS QDs, [ 139 ] CdTe/CdSe QDs, [ 140 ] CdS/ZnSe QDs, [ 141 ] ZnSe/ZnS QDs, [ 142 ] InAs/CdSe/ZnSe QDs, [ 143 ] CuSeS/CdS QDs. [ 144 ] However, charge carriers (mainly electrons) may delocalize to the surface of both Reverse Type‐I and (Quasi‐) Type‐II QDs, which can be easily trapped, making them sensitive to the surrounding environment.…”

Section: Qds‐based Pec Systemmentioning

confidence: 98%

“…Considering their narrow absorption range (mainly UV and visible), a promising future direction would consist in developing processes that can extend their absorption range. The recent development of MXene (2D) QDs, such as Ti 3 C 2 , [ 142 ] is also promising for PEC applications, although the record current density obtained with such systems is less than 3 mA cm −2 . In perspective, their optical response and carrier transport could be improved by co‐sensitization or surface modification.…”

Section: Conclusion and Perspectivementioning

confidence: 99%

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Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

Liu

Zhao

Wang

et al. 2021

Advanced Energy Materials

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opportunity since it is by far the most abundant, sustainable, carbon-neutral, and inexpensive energy source. The theoretical potential of solar power striking the earth's surface is ≈89 300 TW (the integral of the time-and-space-averaged solar flux 342.5 W m −2 over the earth's surface area 5.11 × 10 14 m 2 , estimating that ≈30% and ≈19% are scattered and absorbed by the atmosphere and clouds), [3] which is equivalent to ≈6000 times the power used worldwide every year (estimated at 13.5 TW in 2001, with projected growth up to 27.6 TW by 2050 by the Intergovernmental Panel on Climate Change). [4] In particular, storing solar energy in the form of H 2 presents advantages such as high energy content per mass (143 MJ kg −1), ease of transportation, and cost-effectiveness, [5] thereby addressing the storage challenge which is associated with the diffuse and intermittent character of solar irradiation. Solar energy and water could be converted into H 2 [5b] indirectly by using solar-converted electricity and an electrolyzer, [6] concentrated solar thermal and an electrolyzer, [7] biological and thermochemical processes [8] or directly by photo-/photoelectrocatalysis of water. [1b,f,g] The combination of the energy conversion step with electrolyzers is always limited by the performance of the electrolyzers, whose typical commercial efficiencies are around 73%. [9] Besides, indirect technologies suffer from excessive cost, area requirements, feasibility issues, or energy loss. [10] An alternative direct route is the photo-/photoelectrocatalysis of water, including powdered photocatalysts [11] and photoelectrochemical (PEC) cells. [12] The dispersion of powdered photocatalysts in water is suitable for large-scale processes, while the system requires stirring during the reaction and product separation after the reaction. In comparison, PEC systems (Figure 1a), which combine harvesting solar energy with water reduction into a single device, possesses several advantages. [13] i) PEC reactions address the issue of gas separation by generating products at different electrodes. ii) An external bias supply or self-bias voltage in the PEC system can provide additional energy input to compensate for the potential deficiency, [14] leading to the formation of a surface space charge layer and achieving efficient charge separation and an increased number of long-living photogenerated charges. [15] iii) Moreover, PEC systems can potentially be operated using only stable and abundant materials, such as Cu-based metal oxides, [16] Fe 2 O 3 , [14b,17] and TiO 2. [18] In a typical PEC system, at least one photoelectrode is used as a working electrode to harvest solar radiation, either acting Solar-driven photoelectrochemical (PEC) hydrogen evolution is a promising and sustainable approach to convert solar energy into a fuel that can be stored. Semiconductor quantum dots (QDs) are increasingly used in PEC devices due to their broad composition/size/shape tunable absorption spectrum (from ultraviolet to near-infrared, with significant over...

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Section: Qds‐based Pec Systemmentioning

confidence: 98%

Section: Conclusion and Perspectivementioning

confidence: 99%

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

Liu

Zhao

Wang

et al. 2021

Advanced Energy Materials

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“…[192,193] Because of the unique electronic and magnetic properties of metal nanoparticle, such as Au, Ag, Co, Cu, and Ni, the collective oscillations of the electrons at the surface of nanoparticles will lead to additional light absorption in the visible light region, which is called SPR effect. [194][195][196][197][198][199][200] Therefore, due to the participation of metal nanoparticles, the metal/semiconductor Schottky junction can lead to simultaneous enhancement toward the optical response and carrier separation process.…”

Section: Schottky-junction Engineeringmentioning

confidence: 99%

Engineering Nanostructure–Interface of Photoanode Materials Toward Photoelectrochemical Water Oxidation

et al. 2021

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In practical applications, solar energy is usually converted to other forms of energy, such as electric energy, [9][10][11] chemical energy, [12,13] thermal energy, [14,15] so as to facilitate further transportation and storage. Among them, photoelectrochemical (PEC) reactions from water to hydrogen, CO 2 to C2+ products, and N 2 to NH 3 in the aqueous-based environment have been considered to be quite promising solar-chemical energy conversion pathways. [16][17][18][19] Unlike the traditional water electrolyzing system, the most ideal PEC reaction system can be selfdriven by illumination without external bias. Utilizing the electron-hole carriers generated from the semiconductor photoelectrode, redox reactions take place separately on the photocathode and photoanode. However, as the water oxidation reaction involves a complex four-proton coupled multi-electron process (2H 2 O + 4h + → O 2 + 4H + , E o = 1.23 V vs reversible hydrogen electrode (RHE)), it makes the water oxidation reaction the rate-control step in the watersplitting reaction. [20] Therefore, developing high-performance photo anodes is of great fundamental importance and interest.At the present stage, TiO 2 is the most studied and applied semiconductor photoelectrocatalyst, due to its outstanding chemical stability. [21][22][23] However, as a wide bandgap semiconductor (anatase TiO 2 : 3.2eV, rutile TiO 2 : 3.0 eV), TiO 2 can only respond to the ultraviolet light. Meanwhile, as an intrinsic semiconductor, the bulk/surficial carrier recombination of TiO 2 greatly hinders its practical application. [24][25][26][27] In that case, some narrow bandgap semiconductors are also applied as the photoanode materials, such as Ta 3 N 5 (bandgap 2.1 eV), [28,29] BiVO 4 (bandgap 2.4 eV), and α-Fe 2 O 3 (bandgap 2.1 eV). [30][31][32] However, many of these narrow bandgap materials suffer from poor chemical stability and sluggish interfacial charge injection. [33][34][35] As intrinsic semiconductor materials, both wide and narrow bandgap semiconductor photoanode materials are suffering from the poor bulk-phase carrier separation, intense surficial e − /h + trapping recombination, and sluggish electrode/electrolyte carrier injection kinetics. [36][37][38][39] Fortunately, with the continuous investment of researchers, a series of modification methods have been established and the PEC water oxidation performance of semiconductor photoanode materials has been significantly improved. [32,[40][41][42][43][44] Among various strategies, nanostructure-interface engineering is widely regarded as an effective method to improve the PEC water oxidation performance: [40,41] the light-harvesting performance can be enhanced by the widened optical Photoelectrochemical (PEC) water oxidation based on semiconductor materials plays an important role in the production of clean fuel and value-added chemicals. Nanostructure-interface engineering has proven to be an effective way to construct highly efficient PEC water oxidation photoanodes with good light capture, carrier transport, and ...

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“…According to the Tauc plot function

{(α h v)}^{2} {= (h v ‐ E}_{normalg})

where α is the absorption coefficient, h is the Planck's constant, v is the photon's frequency, and E g is the bandgap. [ 23,24 ] Hence, the bandgaps of ZIF‐Co x Zn 1− x ( x = 1, 0.9, 0.8, 0.7) samples are calculated to be 1.98, 2.00, 2.05, and 2.08 eV (Figure 2b). Considering the Co/Zn ratio in the ZIF‐Co x Zn 1− x ( x = 1, 0.9, 0.8, 0.7) samples, it can be seen that the bandgap shows a quasilinear relationship with the Zn amount increasing (Figure S5–S6, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Multigraded Heterojunction Hole Extraction Layer of ZIF‐Co_xZn_1−x on Co₃O₄/TiO₂ Skeleton for a New Photoanode Architecture in Water Oxidation

et al. 2021

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Multigraded heterojunction (GHJ) attracts increasing attention in solar energy conversion fields due to the controllable carrier transport process. However, it is hard to coordinately manipulate the components and band structure of the photoelectrochemical (PEC) catalyst. Despite the adjustable composition of the metal‐organic framework (MOF), energy band‐engineered MOF materials are rarely used in PEC systems subject to their unclear energy band structure. Herein, a brand new photoanode architecture with MOF‐based multi‐GHJ as the hole extraction channel exhibits outstanding PEC water oxidation performance. ZIF‐CoxZn1−x multi‐GHJs with continuously adjustable energy band structures are obtained by tailoring Co/Zn ratio. ZIF‐CoxZn1−x multi‐GHJ‐modified Co3O4/TiO2 photoanodes (ZIF‐CoxZn1−x/Co3O4/TiO2) exhibit a greatly facilitated carrier separation. ZIF‐Co further causes improved interfacial carrier injection as the water oxidation cocatalyst. By constructing the network‐like Co3O4 skeleton, mass transport and light capture processes are also enhanced. With the synergy of energy band engineering and nanostructure design, the 4‐grade GHJ/Co3O4/TiO2 photoanode shows an excellent photocurrent density (2.91 mA cm−2 at 1.23 V vs. reversible hydrogen electrode) and carrier migration efficiency (73.3%), which are 312% and 554% higher than intrinsic TiO2, respectively. Herein, new insights into energy band‐engineered MOF materials with excellent carrier separation/extraction, which is promising for PEC and other optoelectronic applications, are provided.

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Janus‐Structured Co‐Ti₃C₂ MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

Cited by 116 publications

References 54 publications

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

Engineering Nanostructure–Interface of Photoanode Materials Toward Photoelectrochemical Water Oxidation

Multigraded Heterojunction Hole Extraction Layer of ZIF‐Co_xZn_1−x on Co₃O₄/TiO₂ Skeleton for a New Photoanode Architecture in Water Oxidation

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Janus‐Structured Co‐Ti3C2 MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

Cited by 116 publications

References 54 publications

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

Engineering Nanostructure–Interface of Photoanode Materials Toward Photoelectrochemical Water Oxidation

Multigraded Heterojunction Hole Extraction Layer of ZIF‐CoxZn1−x on Co3O4/TiO2 Skeleton for a New Photoanode Architecture in Water Oxidation

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Janus‐Structured Co‐Ti₃C₂ MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

Multigraded Heterojunction Hole Extraction Layer of ZIF‐Co_xZn_1−x on Co₃O₄/TiO₂ Skeleton for a New Photoanode Architecture in Water Oxidation