In-situ construction of hierarchical CdS/MoS2 microboxes for enhanced visible-light photocatalytic H2 production
TL;DR: In this paper, 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.
About: This article is published in Chemical Engineering Journal.The article was published on 2018-05-01. It has received 145 citations till now. The article focuses on the topics: Photocatalytic water splitting & Photocatalysis.
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TL;DR: A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials.
Abstract: In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.
685 citations
TL;DR: In this paper, the authors highlight the various roles of these 2D materials, such as enhanced light harvesting, suitable band edge alignment, facilitated charge separation, and stability during the water splitting reaction, in various SC/2D photoelectrode and photocatalytic systems.
Abstract: Hydrogen (H2) production via solar water splitting is one of the most ideal strategies for providing sustainable fuel because this requires only water and sunlight. In achieving high-yield production of hydrogen as a recyclable energy carrier, the nanoscale design of semiconductor (SC) materials plays a pivotal role in both photoelectrochemical (PEC) and photocatalytic (PC) water splitting reactions. In this context, the advent of two-dimensional (2D) materials with remarkable electronic and optical characteristics has attracted great attention for their application to PEC/PC systems. The elaborate design of combined 2D layered materials interfaced with other SCs can markedly enhance the PEC/PC efficiencies via bandgap alteration and heterojunction formation. Three classes of 2D materials including graphene, transition metal dichalcogenides (TMDs), and graphitic carbon nitride (g-C3N4), and their main roles in the photoelectrocatalytic production of H2, are discussed in detail herein. We highlight the various roles of these 2D materials, such as enhanced light harvesting, suitable band edge alignment, facilitated charge separation, and stability during the water splitting reaction, in various SC/2D photoelectrode and photocatalytic systems. The roles of emerging 2D nanomaterials, such as 2D metal oxyhalides, 2D metal oxides, and layered double hydroxides, in PEC H2 production are also discussed.
338 citations
TL;DR: Cadmium sulfide (CdS)-based photocatalysts have attracted extensive attention owing to their strong visible light absorption, suitable band energy levels, and excellent electronic charge transportation properties as discussed by the authors.
Abstract: Cadmium sulfide (CdS)-based photocatalysts have attracted extensive attention owing to their strong visible light absorption, suitable band energy levels, and excellent electronic charge transportation properties. This review focuses on the recent progress related to the design, modification, and construction of CdS-based photocatalysts with excellent photocatalytic H2 evolution performances. First, the basic concepts and mechanisms of photocatalytic H2 evolution are briefly introduced. Thereafter, the fundamental properties, important advancements, and bottlenecks of CdS in photocatalytic H2 generation are presented in detail to provide an overview of the potential of this material. Subsequently, various modification strategies adopted for CdS-based photocatalysts to yield solar H2 are discussed, among which the effective approaches aim at generating more charge carriers, promoting efficient charge separation, boosting interfacial charge transfer, accelerating charge utilization, and suppressing charge-induced self-photocorrosion. The critical factors governing the performance of the photocatalyst and the feasibility of each modification strategy toward shaping future research directions are comprehensively discussed with examples. Finally, the prospects and challenges encountered in developing nanostructured CdS and CdS-based nanocomposites in photocatalytic H2 evolution are presented.
258 citations
TL;DR: In this paper, the fundamental aspects of 2D MoS2 cocatalysts have been elaborated, including structural design principles, synthesis strategies, strengths and challenges, and the modification strategies of two-dimensional MoS 2 H2-evolution cocatalyst including doping heteroatoms.
250 citations
TL;DR: In this paper, a Cr doped CoFe layered double hydroxides (LDH) nanosheets array with uniform growth on a nickel-foam (NF) was successfully synthesized.
Abstract: Oxygen evolution reaction (OER) and urea oxidation reaction (UOR) play important roles in the field of hydrogen energy preparation and pollution treatment. In this work, we successfully synthesize a Cr doped CoFe layered double hydroxides (LDH) nanosheets array with uniform growth on a nickel-foam (NF). The partially oxidized Cr6+ during the process of oxidation could adjust the electronic structure and stabilize the high-valence active sites by virtue of its strong electron-withdrawing ability. The calculation of density functional theory (DFT) shows that the incorporation of Cr into CoFe LDH could obviously overcome the step of H2O adsorption during the OER progress. Therefore, the CoFeCr LDH/NF electrode exhibits superior OER performance. Furthermore, when acted as a UOR electrode, its performance is also satisfying. The design of the CoFeCr LDH/NF would hew out a brand-new route to construct more bifunctional electrodes for electrocatalytic water splitting in an alkaline solution with or without urea.
181 citations
References
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TL;DR: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent.
Abstract: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)
8,850 citations
TL;DR: The biggest challenge is whether or not the goals need to be met to fully utilize solar energy for the global energy demand can be met in a costeffective way on the terawatt scale.
Abstract: Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2
8,037 citations
TL;DR: A facile one-pot wet-chemical method is developed to prepare MS2-CdS (M=W or Mo) nanohybrids, which possess a large number of edge sites in the MS2 layers, which are active sites for the HER.
Abstract: Exploration of low-cost and earth-abundant photocatalysts for highly efficient solar photocatalytic water splitting is of great importance. Although transition-metal dichalcogenides (TMDs) showed outstanding performance as co-catalysts for the hydrogen evolution reaction (HER), designing TMD-hybridized photocatalysts with abundant active sites for the HER still remains challenge. Here, a facile one-pot wet-chemical method is developed to prepare MS2–CdS (M=W or Mo) nanohybrids. Surprisedly, in the obtained nanohybrids, single-layer MS2 nanosheets with lateral size of 4–10 nm selectively grow on the Cd-rich (0001) surface of wurtzite CdS nanocrystals. These MS2–CdS nanohybrids possess a large number of edge sites in the MS2 layers, which are active sites for the HER. The photocatalytic performances of WS2–CdS and MoS2–CdS nanohybrids towards the HER under visible light irradiation (>420 nm) are about 16 and 12 times that of pure CdS, respectively. Importantly, the MS2–CdS nanohybrids showed enhanced stability after a long-time test (16 h), and 70 % of catalytic activity still remained.
624 citations
TL;DR: MoS2/CdS p-n heterojunction films with high photoelectrochemical activity for H2 evolution under visible light were successfully prepared by electrodeposition followed by chemical bath deposition as mentioned in this paper.
Abstract: MoS2/CdS p-n heterojunction films with high photoelectrochemical activity for H2 evolution under visible light were successfully prepared by electrodeposition followed by chemical bath deposition. The films were characterized by X-ray diffraction, scanning electron microscopy, UV–visible absorption, X-ray photoemission spectroscopy, photoluminescence, and photoelectrochemical response. The MoS2/CdS heterostructure shows much higher visible-light photoelectrocatalytic activity and higher stability toward the water splitting than pure CdS film. The MoS2/CdS film with an optimal ratio of 0.14% exhibits the highest photocurrent of 28 mA/cm2 and the highest IPCE of ca. 28% at 420 nm at 0 V vs Ag/AgCl. The critical role of MoS2 in the MoS2/CdS film was investigated. The improved photoelectrochemical performance of the MoS2/CdS heterojunction film was attributed to the visible light absorption enhanced by MoS2 and the formation of a p-n junction between CdS and MoS2, which accelerates the effective separation of...
391 citations
TL;DR: With a bandgap of around 2.4 eV, CdS exhibits excellent photocata-lytic activity because of its highly effective absorption of solarenergy.
Abstract: With a bandgap ofaround 2.4 eV, which matches well with the visible spectralrange of solar irradiation, CdS exhibits excellent photocata-lytic activity because of its highly effective absorption of solarenergy. As a visible-light-driven photocatalyst, it has beenextensively investigated and its photocatalytic activity hasbeen found to be influenced by a variety of factors includingpreparation conditions, particle size, morphology, and crys-tallinity.
388 citations