Full Length Article1T phase boosted MoSe2/pg-C3N4 with Z-scheme heterojunction for enhanced photocatalytic degradation of contaminants
Graphical abstract
Introduction
Solar light-driven semiconductor photocatalysis technology has been regarded as a potential strategy for relieving the energy shortage and environmental pollution in recent years [1], [2], [3]. Up to now, the conventional heterojunction (including type-I/II heterojunctions) photocatalyst has been proved for improving the photocatalytic performance, compared to single-component photocatalysts [4], [5]. But the redox activity of electrons and holes decreases because charge carriers transfer and separation in the typical heterojunctions [6], [7]. Thus, Z-scheme heterojunction has gained great attention for photocatalytic applications, since it could improve separation efficiency of charge carriers and retain the strong redox activity simultaneously [8], [9]. Based on the previous researches, Z-scheme heterojunction mainly includes following three typical modes: the charge carriers separate through a reversible redox mediator, an electron mediator or without any mediators [10], [11], [12], [13], [14].
Recently, layered transition-metal dichalcogenides (TMDs: MX2, M = Mo or W, X = S or Se), with two-dimensional (2D) structure and ultrathin thickness, have been used for batteries, electrocatalysis and photocatalysis [15], [16]. However, bulk TMDs materials could not rival other superior catalysts, due to limited active sites and poor conductivity [17]. Various strategies, including phase engineering, edge engineering, defect engineering, doping and heterojunction constructing, have been studied to improve the photocatalytic performance of TMDs materials [18], [19]. Theoretical and experimental studies confirmed that the photocatalytic properties of TMDs are influenced by its electronic structure [20], [21]. For example, MoSe2 materials can be prepared with semiconducting 2H phase (trigonal prismatic coordination) or metastable metallic 1T phase (octahedral coordination) [22]. 2H MoSe2, as a noble-metal-free co-catalyst, has attracted many researchers’ attention for constructing heterojunctions towards photocatalytic hydrogen evolution [23], [24], [25], degrading organic contaminants [26], [27], [28], [29] and Cr (VI) reduction [30], [31]. Compared with 2H MoSe2, 1T MoSe2 with abundant active sites and improved conductivity has been considered as an emerging co-catalyst for photocatalysis [32]. Therefore, phase engineering for transferring 2H phase to 1T phase has been demonstrated as a useful pathway to improve photocatalytic activity. However, most preparation processes of 1T phase MoSe2 are high-consuming and high-risk, including electrochemical lithium insertion, liquid-ammonia-assisted lithiation, chemical vapor deposition and CO2-induced phase-transition [33], [34], [35], [36]. Until now, exploring facile methods of 1T MoSe2-based materials with superior photocatalytic performance is still a great challenge. He et al. synthesized a Si-doped TiO2 nanotube/1T-MoSe2 hybrid, which showed the improved photocatalytic hydrogen evolution activities compared to nanotubes [37]. As the introduction of 1T MoSe2 provided high conductivity, enhanced light absorbance as well as efficient interface-induced effect at the heterojunction. Tao et al. constructed a multiphasic 1T/2H MoSe2 nanosheet integrated with CdS nanorods, which exhibited highly enhanced photocatalytic HER activities than 2H MoSe2/CdS, CdS and Pt/CdS [38]. Since multiphasic 1T/2H MoSe2 co-catalyst has suitable bandgap, dense active sites and improved conductivity than 2H MoSe2 co-catalyst. Xu et al. prepared an interlayer-expanded 1T-MoSe2 for maximizing the co-catalyst activity via optimizing surface activation capacity for photocatalytic HER at edge and basal sites [39]. While the interlayer-expanded 1T-MoSe2 was integrated with 2D-C3N4, the hybrid showed an enhanced HER activity, which was greatly higher than that of 2H-MoSe2 and most noble-metals. Particularly, phase engineering has been widely used as a pathway to enhance the co-catalyst activity for photocatalytic HER performance, but rarely was considered as a potential strategy for the construction of Z-scheme heterojunction towards photocatalytic degradation. As for conventional Z-scheme heterojunctions, most of them required electron mediators at the interface of semiconductors to form the Z-scheme photocatalytic system [10]. The noble-metals, metal materials and carbon-based materials, such as WO3/Ag/CN [40], g-C3N4/Ag/MoS2 [41], BiOCl-Bi-Bi2O3/rGO [42], BiVO4/RGO/Ag3PO4 [43] and Bi2WO6/RGO/g-C3N4 [44], have been investigated as superior electron mediators due to their good conductivity. Similarly, metallic 1T phase MoSe2 might be the promising noble-metal-free material for constructing Z-scheme photocatalytic system.
In this study, different MoSe2 were prepared via a NaBH4-assisted hydrothermal method, and corresponding MoSe2-based composites with 2D proton g-C3N4 (pg-C3N4) were constructed through solvothermal method. Several MoSe2 samples with different phase structure, morphology and light-harvest capacity were obtained by varying the reducing agent (NaBH4) dosage. And the optimal MoSe2 possessed an ordered 1T/2H phase structure, good conductivity and few-layers nanosheet structure with larger specific surface area. Besides, MoSe2 could be employed as co-catalyst over pg-C3N4, forming a Z-scheme heterostructure for photocatalytic degradation. The photocatalytic performance of MoSe2/pg-C3N4 composites was evaluated via degradation of contaminants (TC, RhB) under simulated solar light. And the characterizations demonstrated that the ordered 1T/2H phase MoSe2 provided abundant reactive sites, good light-harvest capacity and efficient transfer as well as separation of charge carriers. Accordingly, the reasonable 1T phase boosted Z-scheme MoSe2-based heterojunction photocatalytic mechanism was proposed.
Section snippets
Materials
Sodium molybdate (Na2MoO4·2H2O, 99%), selenium powder (Se, 99.9%), sodium borohydride (NaBH4, 98%), melamine (C3H6N6, 99%), 1,4-benzoquinone (BQ, 99%), disodium-ethylenediaminetetraacetate (EDTA-2Na, 98%) and isopropyl alcohol (IPA, 99.9%) were obtained from Aladdin Chemistry Co. Ltd. Tetracycline (TC) and RhB were purchased from Sinopharm Chemical Reagent Co., Ltd. All the raw materials are analytic reagent and employed directly.
MoSe2 nanosheets
Synthesis of 2H MoSe2 nanosheets: 1 mmol of Na2MoO4·2H2O, 2 mmol
Structure and property of MoSe2
Several MoSe2 samples with different phase structure were prepared by a NaBH4-assisted hydrothermal method. The XRD patterns and Raman spectra were conducted to determine the phase structures and compositions. In the XRD patterns (Fig. 1a), all the MoSe2 exhibited the similar diffraction peaks corresponding to 2H MoSe2 (JCPDS No. 29-0914). While changing the dosage of NaBH4 (from 4 to 8 mmol), the (0 0 2) peak slight shifted with an angle of ~1° and its intensity decreased compared to MoSe2
Conclusion
Different phase structure and morphology MoSe2 were successfully synthesized by a NaBH4-assisted hydrothermal method. And the optimal MoSe2 possessed an ordered 1T/2H phase structure with good conductivity and few-layers nanosheets structure with larger specific surface area of 29.5 m2/g. Further, MoSe2 was employed as co-catalyst over proton g-C3N4, forming a 2D/2D Z-scheme heterostructure for photocatalytic degradation. 1T/2H MoSe2/pg-C3N4 heterostructure composite had the enhanced
CRediT authorship contribution statement
Yi Wang: Conceptualization, Methodology, Investigation, Data curation, Writing - original draft. Xinyan Xiao: Resources, Writing - review & editing, Supervision. Jiayi Chen: Validation, Formal analysis, Writing - review & editing. Mingli Lu: Validation, Formal analysis, Writing - review & editing. Xingye Zeng: Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (Nos. 21076092, 21376099, 21546002, 21878115).
References (56)
- et al.
Z-scheme plasmonic Ag decorated WO3/Bi2WO6 hybrids for enhanced photocatalytic abatement of chlorinated-VOCs under solar light irradiation
Appl. Catal. B: Environ.
(2019) - et al.
0D (MoS2)/2D (g-C3N4) heterojunctions in Z-scheme for enhanced photocatalytic and electrochemical hydrogen evolution
Appl. Catal. B: Environ.
(2018) - et al.
A rapidly room-temperature-synthesized Cd/ZnS: Cu nanocrystal photocatalyst for highly efficient solar-light-powered CO2 reduction
Appl. Catal. B: Environ.
(2018) - et al.
Exploration of charge carrier delocalization in the iron oxide/CdS type-II heterojunction band alignment for enhanced solar-driven photocatalytic and antibacterial applications
J. Hazard. Mater.
(2019) - et al.
Enhancement mechanism of fiddlehead-shaped TiO2-BiVO4 type II heterojunction in SPEC towards RhB degradation and detoxification
Appl. Surf. Sci.
(2019) - et al.
Respective construction of Type-II and direct Z-scheme heterostructure by selectively depositing CdS on 001 and 101 facets of TiO2 nanosheet with C-dots modification: A comprehensive comparison
J. Hazard. Mater.
(2019) - et al.
Photocatalytic hydrogen evolution and bacterial inactivation utilizing sonochemical-synthesized g-C3N4/red phosphorus hybrid nanosheets as a wide-spectral-responsive photocatalyst: the role of type I band alignment
Appl. Catal. B: Environ.
(2018) - et al.
Construction of iodine vacancy-rich BiOI/Ag@AgI Z-scheme heterojunction photocatalysts for visible-light-driven tetracycline degradation: transformation pathways and mechanism insight
Chem. Eng. J.
(2018) - et al.
Direct Z-scheme photocatalysts: principles, synthesis, and applications
Mater. Today
(2018) - et al.
Facile synthesis of Z-scheme BiVO4/porous graphite carbon nitride heterojunction for enhanced visible-light-driven photocatalyst
Appl. Surf. Sci.
(2018)
Novel reduced graphene oxide-supported Cd0.5Zn0.5S/g-C3N4 Z-scheme heterojunction photocatalyst for enhanced hydrogen evolution
Appl. Surf. Sci.
Recent development of two-dimensional transition metal dichalcogenides and their applications
Mater. Today
Construction of network-like and flower-like 2H-MoSe2 nanostructures coupled with porous g-C3N4 for noble-metal-free photocatalytic H2 evolution under visible light
Appl. Catal. B: Environ.
Construction of Z-scheme MoSe2/CdSe hollow nanostructure with enhanced full spectrum photocatalytic activity
Appl. Catal. B: Environ.
Layered MoSe2/Bi2WO6 composite with P-N heterojunctions as a promising visible-light induced photocatalyst
Appl. Surf. Sci.
Molybdenum diselenide nanosheet/carbon nanofiber heterojunctions: Controllable fabrication and enhanced photocatalytic properties with a broad-spectrum response from visible to infrared light
J. Colloid Interf. Sci.
Direct Z-scheme MoSe2 decorating TiO2 nanotube arrays photocatalyst for water decontamination
Electrochim. Acta
TiO2@MoSe2 line-to-face heterostructure: An advanced photocatalyst for highly efficient reduction of Cr (VI)
Ceram. Int.
Highly efficient solar-driven photocatalytic degradation on environmental pollutants over a novel C fibers@MoSe2 nanoplates core-shell composite
J. Hazard. Mater.
TiO2: Si nanotube/1T-MoSe2 nanosheet hybrids with highly efficient hydrogen evolution catalytic activity
J. Colloid Interf. Sci.
Stable multiphasic 1T/2H MoSe2 nanosheets integrated with 1D sulfide semiconductor for drastically enhanced visible-light photocatalytic hydrogen evolution
Appl. Catal. B: Environ.
Phase and interlayer effect of transition metal dichalcogenide cocatalyst toward photocatalytic hydrogen evolution: The case of MoSe2
Appl. Catal. B: Environ.
Ag nanoparticles decorated WO3/g-C3N4 2D/2D heterostructure with enhanced photocatalytic activity for organic pollutants degradation
Appl. Surf. Sci.
Visible-light-responsive graphene-functionalized Bi-bridge Z-scheme black BiOCl/Bi2O3 heterojunction with oxygen vacancy and multiple charge transfer channels for efficient photocatalytic degradation of 2-nitrophenol and industrial wastewater treatment
Appl. Catal. B: Environ.
Fabrication of BiVO4/RGO/Ag3PO4 ternary composite photocatalysts with enhanced photocatalytic performance
Appl. Surf. Sci.
Construction of Bi2WO6/RGO/g-C3N4 2D/2D/2D hybrid Z-scheme heterojunctions with large interfacial contact area for efficient charge separation and high-performance photoreduction of CO2 and H2O into solar fuels
Appl. Catal. B: Environ.
Rapid synthesis of hierarchical BiOCl microspheres for efficient photocatalytic degradation of carbamazepine under simulated solar irradiation
Chem. Eng. J.
Switching charge transfer of C3N4/W18O49 from type-II to Z-scheme by interfacial band bending for highly efficient photocatalytic hydrogen evolution
Nano Energy
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