Alkali-metals(Li, Na, and K)-adsorbed MoSi2N4 monolayer: the outstanding electronic, optical, and photocatalytic properties investigations

2021 ◽  
Author(s):  
Zhiyuan Sun ◽  
Jing Xu ◽  
Nsajigwa Mwankemwa ◽  
Wen-Xing Yang ◽  
Zao Yi ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Work Function ◽  
Alkali Metals ◽  
Co2 Reduction ◽  
Chemical Properties ◽  
Single Layer ◽  
Chemical Vapor ◽  
Photocatalytic Properties ◽  
Adsorption Processes ◽  
Indirect Band Gap

Abstract Single-layer MoSi2N4, a high-quality two-dimensional material, has recently been fabricated by chemical vapor deposition. Motivated by this latest experimental work, herein, we apply first-principles calculations to investigate the electronic, optical, and photocatalytic properties of alkali-metals(Li, Na, and K)-adsorbed MoSi2N4 monolayer. The electronic structure analysis show that the pristine MoSi2N4 monolayer exhibits an indirect band gap (Eg=1.89 eV). By contrast, the band gaps of one Li-, Na- and K-adsorbed MoSi2N4 monolayers are 1.73, 1.61, and 1.75 eV, respectively. Moreover, the work function of the MoSi2N4 monolayer (4.80eV) is significantly reduced after the adsorption of alkali metal atoms. The work function of one Li-, Na- and K-adsorbed MoSi2N4 monolayers are 1.50, 1.43, and 2.03 eV, respectively. Then, the optical investigations indicate that alkali metal adsorption processes substantially increase the visible light absorption range and coefficient of the MoSi2N4 monolayer. Furthermore, based on redox potential variations after alkali-metals adsorbed, the Li-, and Na-adsorbed MoSi2N4 monolayer are more suitable for water splitting photocatalytic process, and the Li-adsorbed case shows the highest potential application for CO2 reduction. In conclusion, the alkali-metals-adsorbed MoSi2N4 monolayer exhibits promising applications as novel optoelectronic devices and photocatalytic materials due to the unique physical and chemical properties.

Alkali-Metal Containing Amorphous Carbon: Reactivity and Electronic Structure

1999 ◽  
Vol 593 ◽  
Author(s):  
M. Töwe ◽  
P. Reinke ◽  
P. Oelhafen
Keyword(s):  
Electronic Structure ◽  
Alkali Metal ◽  
Work Function ◽  
Photoelectron Spectroscopy ◽  
Alkali Metals ◽  
Film Surface ◽  
Carbon Films ◽  
Metal Atoms ◽  
Sample Characterization

ABSTRACTAmorphous hydrogen-free carbon films (sp2-dominated a-C) were deposited under ultrahigh vacuum conditions between room temperature and 800°C. These films served as matrices for the in-situ incorporation of alkali-metal atoms (Li, Na). In-situ sample characterization was performed by photoelectron spectroscopy with both x-ray and ultraviolet excitation (XPS, UPS). While the clean metal-containing samples were prepared with metal contents of about 10 at%, a strong oxidation driven accumulation of metal atoms on the film surface exceeding 50 at% was observed upon exposure to molecular oxygen. Work-function measurements by UPS reflected the changes within the electronic structure of the material. Metal incorporation considerably decreased the work-function, but only after oxidation we observed work-functions below the values given for pure alkali metals.

Adsorption of alkali metals on graphitic carbon nitride: A first-principles study

2020 ◽  
Vol 34 (32) ◽  
pp. 2050361
Author(s):  
Kaifei Bai ◽  
Zhen Cui ◽  
Enling Li ◽  
Yingchun Ding ◽  
Jiangshan Zheng ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Visible Light ◽  
Work Function ◽  
First Principles ◽  
Density Functional ◽  
Alkali Metals ◽  
Carbon Nitride ◽  
Reduction Rate ◽  
Graphitic Carbon ◽  
Graphitic Carbon Nitride

The electronic and optical properties of the adsorption of alkali metals (Li, Na, K, Rb, Cs) on graphitic carbon nitride (g-C3N[Formula: see text] were calculated and studied based on the first principles of density functional theory. The results investigate that alkali metals adsorbed g-C3N4 has metallic properties, while intrinsic g-C3N4 was semiconducting. Importantly, the charge density differential investigated the charge transfer discovered between the alkali metal and the g-C3N4 monolayer. Meanwhile, the charges (electrons) transfer from the alkali metals to the g-C3N4 system leading to the increase of most carriers in the g-C3N4 system, reducing the resistance of sensors, which is conducive to sensor detection applications. The work function of g-C3N4 decreased from 4.82 eV to 4.09 eV. Especially, the work function of Cs-adsorbed g-C3N4 is the lowest at 4.09 eV, and the reduction rate is 15.15 %, indicating it easier to emit electrons from an external electric field. Moreover, the absorption spectrum of the alkali metal adsorbed on g-C3N4 in the visible light range shows absorption peaks at 380 nm, 412 nm, 420 nm and 476 nm, which cover the visible light area. Thus, the alkali metals adsorbed g-C3N4 system can be used for visible light catalytic. Adsorption of alkali metals can expand the application of g-C3N4 in optoelectronic devices.

scholarly journals Gently Does It!: In Situ Preparation of Alkali Metal - Solid Electrolyte Interfaces for Photoelectron Spectroscopy

2021 ◽  
Author(s):  
Joshua Gibson ◽  
Sudarshan Narayanan ◽  
Jack Swallow ◽  
Pardeep Kumar-Thakur ◽  
Mauro Pasta ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Photoelectron Spectroscopy ◽  
Alkali Metals ◽  
Organic Liquid ◽  
Single Layer ◽  
Metal Deposition ◽  
Single Layer Graphene ◽  
Energy Storage Devices ◽  
Electrolyte Interface

The key charge transfer processes in energy storage devices occur at the electrode-electrolyte interface, which is typically buried making it challenging to access the interfacial chemistry. In the case of Li-ion batteries, metallic Li electrodes hold promise for increasing energy and power densities, and when used in conjunction with solid electrolytes (SEs) adverse safety implications associated with dendrite formation in organic liquid electrolytes can potentially be overcome. To better understand the stability of SEs when in contact with alkali metals and the reactions that occur, here we consider the deposition of thin (~10 nm) alkali metal films onto SE surfaces, that are thin enough that X-ray photoelectron spectroscopy can probe the buried electrode-electrolyte interface. We highlight the importance of in situ alkali metal deposition, by assessing the contaminant species that are present after glovebox handling and the use of ‘inert’ transfer devices. Consequently, we compare and contrast three available methods for in situ alkali-metal deposition; Li sputter deposition, Li evaporation, and Li plating induced by e− flood-gun irradiation. Studies on both a sulphide SE (Li6PS5Cl), and a single-layer graphene probe surface reveal that the more energetic Li deposition methods, such as sputtering, can induce surface damage and interfacial mixing that is not seen with thermal evaporation. This indicates that appropriate selection of the Li deposition method for in situ studies is required to observe representative behaviour, and the results of previous studies involving energetic deposition may warrant further evaluation.

Room Temperature Alkali Metal Reduction of Carbon Dioxide

2020 ◽  
Author(s):  
Lucas A. Freeman ◽  
Akachukwu D. Obi ◽  
Haleigh R. Machost ◽  
Andrew Molino ◽  
Asa W. Nichols ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Room Temperature ◽  
Chemical Reduction ◽  
Bond Cleavage ◽  
Open Shell ◽  
Metal Reduction ◽  
One Pot ◽  
Earth Abundant ◽  
Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO<sub>2</sub> to access useful CO<sub>2</sub>-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO<sub>2</sub> and the MGE. Herein we report the first successful chemical reduction of CO<sub>2</sub> at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO<sub>2</sub> adduct (<b>1</b>) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO<sub>2</sub>)]<sub>n</sub>(M = Li, Na, K, <b> 2</b>-<b>4</b>) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M<sub>2</sub>(CAAC–CO<sub>2</sub>)]<sub>n </sub>(<b>5</b>-<b>8</b>). It is notable that these crystalline clusters of reduced CO<sub>2</sub> may also be isolated via the “one-pot” reaction of free CO<sub>2</sub> with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products <b>2</b>-<b>8</b> were investigated using a combination of experimental and theoretical methods.<br>

scholarly journals Effect of the sample work function on alkali metal dosing induced electronic structure change

2021 ◽  
pp. 147045
Author(s):  
Saegyeol Jung ◽  
Yukiaki Ishida ◽  
Minsoo Kim ◽  
Masamichi Nakajima ◽  
Shigeyuki Ishida ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Alkali Metal ◽  
Work Function ◽  
Structure Change

Graphene nanocomposites: A review on processes, properties, and applications

2021 ◽  
pp. 152808372110242
Author(s):  
Kadir Bilisik ◽  
Mahmuda Akter
Keyword(s):  
Textile Industry ◽  
In Situ Polymerization ◽  
Resin Transfer Molding ◽  
Single Layer ◽  
Chemical Vapor ◽  
Synthesis Process ◽  
Graphene Nanocomposites ◽  
Transfer Molding ◽  
Potential Applications ◽  
Nano Graphene

In this paper, graphene, graphene/matrix, and graphene/fiber nanocomposites, including their synthesis process, fabrication, properties, and potential applications, were reviewed. It was found that several synthesis techniques for nanographene were developed, such as liquid-phase exfoliation and chemical vapor deposition. In addition, some fabrication processes of graphene/matrix and graphene/fiber-based nanocomposites were made, including in-situ polymerization, nanostitching in that single layer nano graphene plate could be interconnected by means of carbon nanotube stitching, resin transfer molding, and vacuum-assisted resin transfer molding. Several properties, including mechanical, thermal, and electrical, on the graphene nanoplatelets materials were summarized in this review paper. It was realized that graphene, graphene/matrix, and graphene/fiber nanocomposites have extraordinary mechanical, thermal, and electrical properties used in advanced engineering applications, including soft robotics, microelectronics, energy storage, biomedical and biosensors as well as textile industry.

scholarly journals 2D MoS2 Encapsulated Silicon Nanopillar Array with High-Performance Light Trapping Obtained by Direct CVD Process

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 267
Author(s):  
Minyu Bai ◽  
Zhuoman Wang ◽  
Jijie Zhao ◽  
Shuai Wen ◽  
Peiru Zhang ◽  
...  
Keyword(s):  
Silicon Substrate ◽  
High Performance ◽  
Low Cost ◽  
Light Trapping ◽  
Incident Light ◽  
Single Layer ◽  
Chemical Vapor ◽  
Optoelectronic Device ◽  
Planar Silicon ◽  
Shortwave Infrared

Weak absorption remains a vital factor that limits the application of two-dimensional (2D) materials due to the atomic thickness of those materials. In this work, a direct chemical vapor deposition (CVD) process was applied to achieve 2D MoS2 encapsulation onto the silicon nanopillar array substrate (NPAS). Single-layer 2D MoS2 monocrystal sheets were obtained, and the percentage of the encapsulated surface of NPAS was up to 80%. The reflection and transmittance of incident light of our 2D MoS2-encapsulated silicon substrate within visible to shortwave infrared were significantly reduced compared with the counterpart planar silicon substrate, leading to effective light trapping in NPAS. The proposed method provides a method of conformal deposition upon NPAS that combines the advantages of both 2D MoS2 and its substrate. Furthermore, the method is feasible and low-cost, providing a promising process for high-performance optoelectronic device development.

scholarly journals Alkali metal doping of black phosphorus monolayer for ultrasensitive capture and detection of nitrogen dioxide

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Azam Marjani ◽  
Mehdi Ghambarian ◽  
Mohammad Ghashghaee
Keyword(s):  
Alkali Metal ◽  
Nitrogen Dioxide ◽  
Work Function ◽  
Black Phosphorus ◽  
Research Interest ◽  
Metal Doping ◽  
Li Doping ◽  
Rational Development ◽  
Parallel Configuration ◽  
First Time

AbstractBlack phosphorus nanostructures have recently sparked substantial research interest for the rational development of novel chemosensors and nanodevices. For the first time, the influence of alkali metal doping of black phosphorus monolayer (BP) on its capabilities for nitrogen dioxide (NO2) capture and monitoring is discussed. Four different nanostructures including BP, Li-BP, Na-BP, and K-BP were evaluated; it was found that the adsorption configuration on Li-BP was different from others such that the NO2 molecule preferred a vertical stabilization rather than a parallel configuration with respect to the surface. The efficiency for the detection increased in the sequence of Na-BP < BP < K-BP < Li-BP, with the most significant improvement of + 95.2% in the case of Li doping. The Na-BP demonstrated the most compelling capacity (54 times higher than BP) for NO2 capture and catalysis (− 24.36 kcal/mol at HSE06/TZVP). Furthermore, the K-doped device was appropriate for both nitrogen dioxide adsorption and sensing while also providing the highest work function sensitivity (55.4%), which was much higher than that of BP (10.4%).

scholarly journals Spotlight on Alkali Metals: The Structural Chemistry of Alkali Metal Thallides

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1013
Author(s):  
Stefanie Gärtner
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Crystal Structures ◽  
Alkali Metals ◽  
Valence Electron ◽  
Oxidation States ◽  
Valence Electron Concentration ◽  
Base Metals ◽  
Charge Balancing

Alkali metal thallides go back to the investigative works of Eduard Zintl about base metals in negative oxidation states. In 1932, he described the crystal structure of NaTl as the first representative for this class of compounds. Since then, a bunch of versatile crystal structures has been reported for thallium as electronegative element in intermetallic solid state compounds. For combinations of thallium with alkali metals as electropositive counterparts, a broad range of different unique structure types has been observed. Interestingly, various thallium substructures at the same or very similar valence electron concentration (VEC) are obtained. This in return emphasizes that the role of the alkali metals on structure formation goes far beyond ancillary filling atoms, which are present only due to charge balancing reasons. In this review, the alkali metals are in focus and the local surroundings of the latter are discussed in terms of their crystallographic sites in the corresponding crystal structures.

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