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Journal ArticleDOI: 10.1039/D0CY02100H

Lamellar flower-like porous MoS2 as an efficient cocatalyst to boost photocatalytic hydrogen evolution of CdS

02 Mar 2021-Catalysis Science & Technology (The Royal Society of Chemistry)-Vol. 11, Iss: 4, pp 1292-1297
Abstract: Photocatalysts with novel structure and superior hydrogen (H2) evolution activity are attractive to solve energy shortage and other environmental problems. As one of two-dimensional transition metal disulfides (2D TMDs), MoS2 cocatalyst with a unique lamellar flower-like porous structure was fabricated herein to boost the photocatalytic H2 evolution of CdS. The porous MoS2/CdS photocatalyst reached a H2 evolution activity of 54.1 mmol h−1 g−1, which is 36 times better than in case of pure CdS. Characterizations demonstrated that the promoted activity of the porous MoS2/CdS composite was strongly related to the distinctive cocatalyst structure. The coexistence of spherical porous and lamellar structures, as well as a heterojunction structure between MoS2 and CdS played crucial roles. A slow photo effect helped to enhance the visible-light utilization. The heterojunction structure of CdS particles with lamellar MoS2 accelerated the transfer of photo-induced electrons. This unique porous 2D TMD structure as a cocatalyst is expected to enhance activities for H2 evolution of other photocatalysts as well.

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Topics: Lamellar structure (52%)

6 results found

Open accessJournal ArticleDOI: 10.1016/J.MTSUST.2021.100073
Nishanth Thomas1, Snehamol Mathew1, Keerthi M. Nair1, Kris O’Dowd1  +4 moreInstitutions (1)
01 Sep 2021-
Abstract: Two-dimensional (2D) molybdenum disulfide (MoS2)–based materials are of great interest because of their capacity to efficiently absorb electromagnetic spectrum in the visible region. Starting from the structural and electronic properties, this review discusses the synthesis strategies of 2D MoS2. The major photocatalytic applications of 2D MoS2 such as hydrogen evolution, pollutant degradation, self-cleaning, photoelectrochemical water splitting, and microbial disinfection are summarized. The mechanistic understanding of various photocatalytic applications of 2D MoS2 is summarized through schematic diagrams. In addition, this review outlines the methodologies for improving the 2D MoS2 photocatalysts and recapitulates the research directions in this area of semiconductor photocatalysis.

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Topics: Water splitting (52%)

5 Citations

Open accessJournal ArticleDOI: 10.1039/D1RA03657B
Daria Ryaboshapka1, Pavel Afanasiev1Institutions (1)
15 Jun 2021-RSC Advances
Abstract: Carbon nitride C3N4 has been used as a sacrificial template to prepare inorganic materials with hierarchical pore structure. C3N4 impregnated with ammonium heptamolybdate was treated in reactive gas mixtures (H2S/H2 or NH3/H2). This approach allowed mesoporous molybdenum sulfide and molybdenum nitride materials to be obtained that replicate the morphology of the C3N4 template. Advantageous catalytic properties have been demonstrated in the thiophene hydrodesulfurization (HDS) and electrochemical hydrogen evolution reaction (HER). The highest rates in both reactions were observed for partially sulfidized Mo2N solid.

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Topics: Nitride (65%), Carbon nitride (63%), Ammonium heptamolybdate (56%) ... show more

Journal ArticleDOI: 10.1016/J.MSSP.2021.106128
Guoping Jiang1, Chaoyue Zheng1, Zhiliang Jin1Institutions (1)
Abstract: Hexagonal CdS and layered double hydroxides are the hot materials for photocatalytic hydrogen evolution reaction due to their unique structure and excellent performance. Here, CdS/NiCo LDH catalyst with S-scheme heterogeneous is successfully prepared by the method of electrostatic self-assembly. Compared with CdS, the hydrogen evolution performance over the appropriate CdS/NiCo LDH is increased by 3.6 times. This is because the tight coupling of the contact interface between CdS and NiCo LDH and the matching of the band gap structure improve the transmission efficiency of photogenerated electrons. Ultraviolet–visible and photoluminescence experiments have proved that the separation efficiency of electrons and holes, the light absorption intensity and the charge lifetime of the composite catalyst have been greatly improved. Additional series of characterization prove the possible S-scheme heterojunction mechanism of CdS/NiCo LDH photocatalytic hydrogen evolution.

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Open accessJournal ArticleDOI: 10.1016/J.JPHOTOCHEM.2021.113550
Abstract: Heterogeneous photocatalysis have been considered an important and efficient alternative water and wastewater treatment process. In this area, different semiconductors, such as tungsten trioxide, have been investigated aiming to enhance photocatalytic performance. WO3 is known to be an efficient material with high stability in acidic conditions. In the present work, pure and Ag/AgCl-doped WO3 photocatalysts were synthesized by a simple hydrothermal method. A discussion of the effects of two pH-controlling agents, HCl and HNO3, in the final properties of the catalyst is reported for the first time. The materials were characterized by XRD, BET, SEM, EDS and UV–vis DRS. All catalysts showed similar or enhanced band gap values compared to a standard photocatalyst benchmark (TiO2 P25). The type of acid did not lead to significant differences in morphology or photocatalytic activity of undoped catalysts. In contrast, doped catalysts prepared using HCl resulted in particles of flower-like morphology, with higher uniformity and slightly narrower band gap values. Furthermore, the use of HCl in the synthesis of silver-doped WO3 resulted in catalysts containing AgCl, while Ag0 was the major dopant species when HNO3 was used. All materials exhibited good photocatalytic activity, with a maximum of 75.4% acetaminophen degradation under simulated sunlight achieved by the catalyst prepared with HCl and doped with 5% Ag-equivalent. For this catalyst, the degradation kinetics was found to be consistent with the Langmuir-Hinshelwood (L−H) model, and reusability tests showed no significant decrease in the degradation efficiency after four cycles. Finally, the effects of different scavengers suggest that O2•− species play a major role in acetaminophen degradation with the material containing WO3, Ag and AgCl.

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Topics: Photocatalysis (55%), Tungsten trioxide (54%), Catalysis (50%)

Open accessJournal ArticleDOI: 10.1021/ACSOMEGA.1C02453
22 Jul 2021-
Abstract: WO3/CeO2 heterostructured nanocomposites containing different WO3 ratios (0.1, 0.3, 0.5, and 1.0 wt %) were synthesized by a precipitation method. The coupling of CeO2 and WO3 with a high specific surface area noticeably enhanced the photocatalytic activity of indigo carmine (IC) degradation under visible-light irradiation. The degradation rate constants (k) of 0.5 wt % WO3/CeO2 nanocomposites reached 4 and 5 times higher than those of CeO2 and WO3, respectively. Regarding the experimental results, the X-ray diffraction (XRD) patterns of the CeO2 spherical nanoparticles and rod-shaped WO3 were assigned to the cubic fluorite and orthorhombic phase structures, respectively. The increasing photocatalytic activity of nanocomposite samples could be attributed to the heterojunction of the photocatalysts with efficient charge separation and strong oxidative ability, which were confirmed by the photoluminescence spectra and diffuse reflectance spectrometry. The staggered heterojunction of the nanocomposite promoted efficient electron transfer and suppressed the recombination of photogenerated electrons and holes during the process.

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Topics: Indigo carmine (60%), Photocatalysis (51%), Nanocomposite (50%)


29 results found

Journal ArticleDOI: 10.1039/C8CS00324F
Jinbo Pang1, Rafael G. Mendes2, Rafael G. Mendes1, Alicja Bachmatiuk3  +12 moreInstitutions (6)
Abstract: Transition metal carbides and nitrides (MXenes), a family of two-dimensional (2D) inorganic compounds, are materials composed of a few atomic layers of transition metal carbides, nitrides, or carbonitrides. Ti3C2, the first 2D layered MXene, was isolated in 2011. This material, which is a layered bulk material analogous to graphite, was derived from its 3D phase, Ti3AlC2 MAX. Since then, material scientists have either determined or predicted the stable phases of >200 different MXenes based on combinations of various transition metals such as Ti, Mo, V, Cr, and their alloys with C and N. Extensive experimental and theoretical studies have shown their exciting potential for energy conversion and electrochemical storage. To this end, we comprehensively summarize the current advances in MXene research. We begin by reviewing the structure types and morphologies and their fabrication routes. The review then discusses the mechanical, electrical, optical, and electrochemical properties of MXenes. The focus then turns to their exciting potential in energy storage and conversion. Energy storage applications include electrodes in rechargeable lithium- and sodium-ion batteries, lithium-sulfur batteries, and supercapacitors. In terms of energy conversion, photocatalytic fuel production, such as hydrogen evolution from water splitting, and carbon dioxide reduction are presented. The potential of MXenes for the photocatalytic degradation of organic pollutants in water, such as dye waste, is also addressed, along with their promise as catalysts for ammonium synthesis from nitrogen. Finally, their application potential is summarized.

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Topics: MXenes (73%), Energy storage (52%), Supercapacitor (50%)

715 Citations

Journal ArticleDOI: 10.1021/JACS.8B12428
Yuting Xiao1, Guohui Tian1, Wei Li2, Ying Xie1  +4 moreInstitutions (2)
Abstract: Polymeric carbon nitride (C3N4) has emerged as the most promising candidate for metal-free photocatalysts but is plagued by low activity due to the poor quantum efficiency and low specific surface area. Exfoliation of bulk crystals into ultrathin nanosheets has proven to be an effective and widely used strategy for enabling high photocatalytic performances; however, this process is complicated, time-consuming, and costly. Here, we report a simple bottom-up method to synthesize porous few-layer C3N4, which involves molecule self-assembly into layered precursors, alcohol molecules intercalation, and subsequent thermal-induced exfoliation and polycondensation. The as-prepared few-layer C3N4 expose more active sites and greatly enhance the separation of charge carriers, thus exhibiting a 26-fold higher hydrogen evolution activity than bulk counterpart. Furthermore, we find that both the high activity and selectivity for the oxidative coupling of amines to imines can be obtained under visible light that surpass those of other metal-free photocatalysts so far.

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Topics: Carbon nitride (54%), Exfoliation joint (52%), Photoredox catalysis (52%)

320 Citations

Journal ArticleDOI: 10.1016/J.APCATB.2017.08.046
Hao Zhang1, Jinmeng Cai1, Yating Wang1, Moqing Wu1  +8 moreInstitutions (3)
Abstract: This paper describes the effects of defect distribution on energy band structure and the subsequent photocatalytic activity over TiO2 with exposed {001} facets as the model catalyst. Our results show that only surface oxygen vacancies (Vo’s) and Ti3+ centers in TiO2 can be induced by hydrogenation treatment, whereas the generation of bulk Vo’s and Ti3+ species depends on the thermal treatment in nitrogen. Both the surface and bulk defects in TiO2 can promote the separation of electron-hole pairs, enhance the light absorption, and increase the donor density. The presence of surface and bulk defects in TiO2 can not change the valence band maximum, but determine the conduction band minimum. Surface defects in TiO2 induce a tail of conduction band located above the H+/H2 redox potential, which benefits the photocatalytic performance. However, bulk defects in TiO2 generate a band tail below the H+/H2 potential, which inhibits hydrogen production. Thus, the change of band gap structure by defects is the major factor to determine the photocatalytic activity of TiO2 for hydrogen evolution. It is a new insight into the rational design and controllable synthesis of defect-engineered materials for various catalytic processes.

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Topics: Band gap (61%), Electronic band structure (51%)

122 Citations

Journal ArticleDOI: 10.1039/B708474A
Abstract: A driving force in the rapidly developing field of photonic crystals has been the photonic bandgap, a range of energies where the propagation of light is completely forbidden. The photonic bandgap allows the design of photonic lattices that localize, guide and bend light at sub-micron length scales, providing opportunities for the creation of miniature optical devices and integrated optical circuits to help drive the revolution in photonics. A less well known attribute of photonic crystals is their theoretical ability to slow light to a velocity of zero. This phenomenon can be achieved at the high and low energy edges of photonic stopgaps where the photonic bands are flat and light exists as a standing wave commensurate with the photonic lattice and travels at a group velocity of zero, referred to as “slow photons” herein. It has been shown theoretically that the probability of harvesting slow photons scales inversely with their group velocity. This means that a number of well known photon driven processes and devices in chemistry and physics can be enhanced by capturing this unique property of slow photons. In this paper we will look at slow photons mainly through the eye of chemistry and highlight some recent developments in this exciting and emerging field that demonstrate the potential of slow photons in materials chemistry and nanochemistry.

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Topics: Photonic crystal (62%), Slow light (62%), Photonics (55%) ... show more

114 Citations

Journal ArticleDOI: 10.1016/J.CEJ.2018.01.124
Yu Liu1, Haoting Niu1, Wei Gu1, Xiaoyu Cai1  +3 moreInstitutions (1)
Abstract: Exploration of highly active and noble-metal-free photocatalysts for high-efficiency photocatalytic water splitting is of great importance. Herein, a facile and effective in-situ hydrothermal method has been developed for preparation of CdS/MoS2 heterostructures with a unique hollow microbox morphology for visible-light-driven water splitting into H2. The influence of MoS2 is systematically investigated in terms of optical properties and photocatalytic activity of the CdS/MoS2 microboxes by varying the concentration of sodium molybdate. Under visible-light irradiation (λ ≥ 420 nm), the CdS/MoS2 microboxes exhibit superior photocatalytic H2 evolution activity (1.36 mmol/g/h) compared to pure CdS microboxes (0.04 mmol/g/h), corresponding to an apparent quantum yield of 14.5% at 420 nm. Photocatalytic mechanism study proves that the MoS2 nanosheets can serve as a co-catalyst and electron acceptor, for the effective promotion of electron transfer and separation of photogenerated charge carriers from CdS to further stimulate the surface H2 evolution kinetics. Furthermore, the well-defined interior voids, low density and shell permeability of the hierarchical CdS/MoS2 microboxes also contribute to the improvement of the photocatalytic performance.

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112 Citations