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Chemical Functionalization of Two-Dimensional Materials

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 28049

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Special Issue Editor

Prof. Dr. Jing Li

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Guest Editor

Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing 100191, China
Interests: surface chemistry of low-dimensional materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

2D materials are crystalline sheets with atomic thickness. The unique structural features and exotic properties of 2D materials render them some of the most appealing candidates for a wide range of potential applications. To this end, research on functionalization of 2D materials has grown rapidly over the past several years and attracted immense attention from scientists from physics, chemistry, engineering, medicine and industry.

To attract broad interest toward 2D materials, we organize the present Special Issue in Molecules to provide an insightful overview and summarize the recent advances in chemically relevant functionalization toward 2D materials. The scope of this special topic will address the recent chemistry trends in 2D materials, and their widespread applications in functional devices.

We are pleased to invite you to submit manuscripts for the Special Issue in the form of full research papers, communications, perspectives and review articles. Topics covered in this Special Issue include, but might not be limited to:

Synthesis and novel properties;
Nanotechnology;
2D heterostructure and derivatives;
Applications: energy, environment, electronics, photonics, bioloby, etc.

Prof. Dr. Jing Li
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

two-dimensional materials
chemical modulation, surface modification
functionalization
layered materials
monolayer
molecular engineering, processing and applications

Published Papers (14 papers)

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Research

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14 pages, 4403 KiB

Open AccessArticle

A Superior Two-Dimensional Phosphorus Flame Retardant: Few-Layer Black Phosphorus

by Taiming Zhang, Huanyu Xie, Shuai Xie, Ajuan Hu, Jie Liu, Jian Kang, Jie Hou, Qing Hao, Hong Liu and Hengxing Ji

Molecules 2023, 28(13), 5062; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28135062 - 28 Jun 2023

Cited by 6 | Viewed by 1416

Abstract

The usage of flame retardants in flammable polymers has been an effective way to protect both lives and material goods from accidental fires. Phosphorus flame retardants have the potential to be follow-on flame retardants after halogenated variants, because of their low toxicity, high efficiency and compatibility. Recently, the emerging allotrope of phosphorus, two-dimensional black phosphorus, as a flame retardant has been developed. To further understand its performance in flame-retardant efficiency among phosphorus flame retardants, in this work, we built model materials to compare the flame-retardant performances of few-layer black phosphorus, red phosphorus nanoparticles, and triphenyl phosphate as flame-retardant additives in cellulose and polyacrylonitrile. Aside from the superior flame retardancy in polyacrylonitrile, few-layer black phosphorus in cellulose showed the superior flame-retardant efficiency in self-extinguishing, ~1.8 and ~4.4 times that of red phosphorus nanoparticles and triphenyl phosphate with similar lateral size and mass load (2.5~4.8 wt%), respectively. The char layer in cellulose coated with the few-layer black phosphorus after combustion was more continuous and smoother than that with red phosphorus nanoparticles, triphenyl phosphate and blank, and the amount of residues of cellulose coated with the few-layer black phosphorus in thermogravimetric analysis were 10 wt%, 14 wt% and 14 wt% more than that with red phosphorus nanoparticles, triphenyl phosphate and blank, respectively. In addition, although exothermic reactions, the combustion enthalpy changes in the few-layer black phosphorus (−127.1 kJ mol⁻¹) are one third of that of red phosphorus nanoparticles (−381.3 kJ mol⁻¹). Based on a joint thermodynamic, spectroscopic, and microscopic analysis, the superior flame retardancy of the few-layer black phosphorus was attributed to superior combustion reaction suppression from the two-dimensional structure and thermal nature of the few-layer black phosphorus. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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21 pages, 8354 KiB

Open AccessArticle

Revealing the Combined Effect of Active Sites and Intra-Particle Diffusion on Adsorption Mechanism of Methylene Blue on Activated Red-Pulp Pomelo Peel Biochar

by Fang Wei, Shenglong Jin, Chunyi Yao, Tianhao Wang, Shengpu Zhu, Yabiao Ma, Heng Qiao, Linxi Shan, Rencong Wang, Xiaoxue Lian, Xiaoqiang Tong, Yan Li, Qiang Zhao and Weiguo Song

Molecules 2023, 28(11), 4426; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28114426 - 29 May 2023

Cited by 3 | Viewed by 1205

Abstract

Phosphoric acid-activated biochar has been proven to be a promising adsorbent for pollutant removal in an aqueous solution. It is urgent to understand how surface adsorption and intra-particle diffusion synergistically contribute to the adsorption kinetic process of dyes. In this work, we prepared a series of PPC adsorbents (PPCs) from red-pulp pomelo peel under different pyrolysis temperatures (150–350 °C), which have a broad specific surface area range from 3.065 m²/g to 1274.577 m²/g. The active sites on the surface of PPCs have shown specific change laws of decreasing hydroxyl groups and increasing phosphate ester groups occurring as the pyrolysis temperature rises. Both reaction models (PFO and PSO models) and diffusion models (intra-particle diffusion models) have been applied to simulate the adsorption experimental data to verify the hypothesis deduced from the Elovich model. PPC-300 exhibits the highest adsorption capacity of MB (423 mg/g) under given conditions. Due to its large quantities of active sites on the external and internal surfaces (1274.577 m²/g), a fast adsorption equilibrium can be achieved within 60 min (with an initial MB concentration of 100 ppm). PPC-300 and PPC-350 also exhibit an intra-particle-diffusion-controlled adsorption kinetic process with a low initial MB concentration (100 ppm) or at the very beginning and final stage of adsorption with a high initial MB concentration (300 ppm) at 40 °C, considering that the diffusion is likely hindered by adsorbate molecules through internal pore channels at the middle stage of adsorption in these cases. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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12 pages, 9478 KiB

Open AccessArticle

Novel Functionalized Boron Nitride Nanosheets Achieved by Radiation-Induced Oxygen Radicals and Their Enhancement for Polymer Nanocomposites

by Xin Yang, Bingling Zhao, Liudi Ji, Peng Hu, Xiaoming Zhu and Zeyu Li

Molecules 2023, 28(8), 3444; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28083444 - 13 Apr 2023

Cited by 1 | Viewed by 1212

Abstract

Boron nitride nanosheets (BNNSs) exfoliated from hexagonal boron nitride (h-BN) show great potential in polymer-based composites due to their excellent mechanical properties, highly thermal conductivity, and insulation properties. Moreover, the structural optimization, especially the surface hydroxylation, of BNNSs is of importance to promote their reinforcements and optimize the compatibility of its polymer matrix. In this work, BNNSs were successfully attracted by oxygen radicals decomposed from di-tert-butylperoxide (TBP) induced by electron beam irradiation and then treated with piranha solution. The structural changes of BNNSs in the modification process were deeply studied, and the results demonstrate that the as-prepared covalently functionalized BNNSs possess abundant surface hydroxyl groups as well as reliable structural integrity. Of particular importance is that the yield rate of the hydroxyl groups is impressive, whereas the usage of organic peroxide and reaction time is greatly reduced due to the positive effect of the electron beam irradiation. The comparisons of PVA/BNNSs nanocomposites further indicate that the hydroxyl-functionalized BNNSs effectively promote mechanical properties and breakdown strength due to the enhanced compatibility and strong two-phase interactions between nanofillers and the polymer matrix, which further verify the application prospects of the novel route proposed in this work. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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14 pages, 2836 KiB

Open AccessArticle

Preparation of Biochar with Developed Mesoporous Structure from Poplar Leaf Activated by KHCO₃ and Its Efficient Adsorption of Oxytetracycline Hydrochloride

by Zhenhua Wei, Chao Hou, Zhishuo Gao, Luolin Wang, Chuansheng Yang, Yudong Li, Kun Liu and Yongbin Sun

Molecules 2023, 28(7), 3188; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28073188 - 3 Apr 2023

Cited by 5 | Viewed by 1584

Abstract

The effective removal of oxytetracycline hydrochloride (OTC) from the water environment is of great importance. Adsorption as a simple, stable, and cost-effective technology is regarded as an important method for removing OTC. Herein, a low-cost biochar with a developed mesoporous structure was synthesized via pyrolysis of poplar leaf with potassium bicarbonate (KHCO₃) as the activator. KHCO₃ can endow biochar with abundant mesopores, but excessive KHCO₃ cannot continuously promote the formation of mesoporous structures. In comparison with all of the prepared biochars, PKC-4 (biochar with a poplar leaf to KHCO₃ mass ratio of 5:4) shows the highest adsorption performance for OTC as it has the largest surface area and richest mesoporous structure. The pseudo-second-order kinetic model and the Freundlich equilibrium model are more consistent with the experimental data, which implies that the adsorption process is multi-mechanism and multi-layered. In addition, the maximum adsorption capacities of biochar are slightly affected by pH changes, different metal ions, and different water matrices. Moreover, the biochar can be regenerated by pyrolysis, and its adsorption capacity only decreases by approximately 6% after four cycles. The adsorption of biochar for OTC is mainly controlled by pore filling, though electrostatic interactions, hydrogen bonding, and π-π interaction are also involved. This study realizes biomass waste recycling and highlights the potential of poplar leaf-based biochar for the adsorption of antibiotics. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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12 pages, 2122 KiB

Open AccessArticle

Ratiometric Near-Infrared Fluorescence Liposome Nanoprobe for H₂S Detection In Vivo

by Luyan Wu, Yili Liu, Junya Zhang, Yinxing Miao and Ruibing An

Molecules 2023, 28(4), 1898; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28041898 - 16 Feb 2023

Cited by 1 | Viewed by 1441

Abstract

Accurate detection of H₂S is crucial to understanding the occurrence and development of H₂S-related diseases. However, the accurate and sensitive detection of H₂S in vivo still faces great challenges due to the characteristics of H₂S diffusion and short half-life. Herein, we report a H₂S-activatable ratiometric near-infrared (NIR) fluorescence liposome nanoprobe HS-CG by the thin-film hydration method. HS-CG shows “always on” fluorescence signal at 816 nm and low fluorescence signal at 728 nm; the NIR fluorescence ratio between 728 and 816 nm (F₇₂₈/F₈₁₆) is low. Upon reaction with H₂S, the fluorescence at 728 nm could be more rapidly turned on due to strong electrostatic interaction between enriched HS⁻ and positively charged 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC) doped in the liposome nanoprobe HS-CG, resulting in a large enhancement of F₇₂₈/F₈₁₆, which allows for sensitive visualization of the tumor H₂S levels in vivo. This study demonstrates that this strategy of electrostatic adsorption between HS⁻ and positively charged molecules provides a new way to enhance the reaction rate of the probe and H₂S, thus serving as an effective platform for improving the sensitivity of imaging. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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15 pages, 8156 KiB

Open AccessArticle

MoS₂ Nanosheets Decorated with Fe₃O₄ Nanoparticles for Highly Efficient Solar Steam Generation and Water Treatment

by Zhi Bai, Haifeng Xu, Guang Li, Bo Yang, Jixin Yao, Kai Guo and Nan Wang

Molecules 2023, 28(4), 1719; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28041719 - 10 Feb 2023

Cited by 4 | Viewed by 1533

Abstract

The shortage of water resources has always been one of the most difficult problems that perplexes humanity. Solar steam generation (SSG) has been a new non-polluting and low-cost water purification method in recent years. However, the high cost of traditional photothermal conversion materials and the low efficiency of photothermal conversion has restricted the large-scale application of SSG technology. In this work, composite materials with Fe₃O₄ nanospheres attached to MoS₂ nanosheets were synthesized, which increased the absorbance and specific surface area of the composite materials, reduced the sunlight reflection, and increased the photothermal conversion efficiency. During the experiment, the composite material was evenly coated on cotton. The strong water absorption of cotton ensured that the water could be transported sufficiently to the surface for evaporation. Under one sun irradiation intensity, the evaporation rate of the sample synthesized in this work reached 1.42 kg m⁻² h⁻¹; the evaporation efficiency is 89.18%. In addition, the surface temperature of the sample can reach 41.6 °C, which has far exceeded most photothermal conversion materials. Furthermore, the use of this composite material as an SSG device for seawater desalination and sewage purification can remove more than 98% of salt ions in seawater, and the removal rate of heavy metal ions in sewage is close to 100%, with a good seawater desalination capacity and sewage purification capacity. This work provides a new idea for the application of composite materials in the field of seawater desalination and sewage purification. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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13 pages, 4526 KiB

Open AccessArticle

Interfaces and Oxygen Vacancies-Enriched Catalysts Derived from Cu-Mn-Al Hydrotalcite towards High-Efficient Water–Gas Shift Reaction

by Hanci Li, Zhenyi Xiao, Pei Liu, Hairu Wang, Jiajun Geng, Huibin Lei and Ou Zhuo

Molecules 2023, 28(4), 1522; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28041522 - 4 Feb 2023

Cited by 1 | Viewed by 1521

Abstract

The water–gas shift (WGS) reaction is an important process in the hydrogen industry, and its catalysts are of vital importance for this process. However, it is still a great challenge to develop catalysts with both high activity and high stability. Herein, a series of high-purity Cu-Mn-Al hydrotalcites with high Cu content have been prepared, and the WGS performance of the Cu-Mn-Al catalysts derived from these hydrotalcites have been studied. The results show that the Cu-Mn-Al catalysts have both outstanding catalytic activity and excellent stability. The optimized Cu-Mn-Al catalyst has displayed a superior reaction rate of 42.6

{μ mol}_{CO}^{- 1} \cdot g_{cat}^{- 1} \cdot s^{- 1}

, while the CO conversion was as high as 96.1% simultaneously. The outstanding catalytic activities of the Cu-Mn-Al catalysts could be ascribed to the enriched interfaces between Cu-containing particles and manganese oxide particles, and/or abundant oxygen vacancies. The excellent catalytic stability of the Cu-Mn-Al catalysts may be benefitting from the low valence state of the manganese of manganese oxides, because the low valence manganese oxides have good anti-sintering properties and can stabilize oxygen vacancies. This study provides an example for the construction of high-performance catalysts by using two-dimensional hydrotalcite materials as precursors. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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9 pages, 2283 KiB

Open AccessCommunication

Tunability of the Superconductivity of NbSe₂ Films Grown by Two-Step Vapor Deposition

by Huihui Lin, Meijuan Chang, Xingjie Fu, Pengfei Li, Maoxin Chen, Luyan Wu, Fangqi Yang and Quan Zhang

Molecules 2023, 28(3), 1059; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28031059 - 20 Jan 2023

Cited by 2 | Viewed by 2379

Abstract

Layered metallic transition-metal dichalcogenides (TMDCs) are ideal platforms for exploring their fascinating electronic properties at two-dimensional limits, such as their charge density wave (CDW) and superconductivity. Therefore, developing ways to improve the crystallization quality of TMDCs is urgently needed. Here we report superconductively tunable NbSe₂ grown by a two-step vapor deposition method. By optimizing the sputtering conditions, superconducting NbSe₂ films were prepared from highly crystalline Nb films. The bilayer NbSe₂ films showed a superconducting transition temperature that was up to 3.1 K. Similar to the salt-assisted chemical vapor deposition (CVD) method, superconducting monolayer NbSe₂ crystals were also grown from a selenide precursor, and the growth strategy is suitable for many other TMDCs. Our growth method not only provides a way to improve the crystalline quality of TMDC films, but also gives new insight into the growth of monolayer TMDCs. It holds promise for exploring two-dimensional TMDCs in fundamental research and device applications. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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13 pages, 2593 KiB

Open AccessArticle

A Heterostructure Photoelectrode Based on Two-Dimensional Covalent Organic Framework Film Decorated TiO₂ Nanotube Arrays for Enhanced Photoelectrochemical Hydrogen Generation

by Yue Zhang, Yujie Li, Jing Yu, Bing Sun and Hong Shang

Molecules 2023, 28(2), 822; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28020822 - 13 Jan 2023

Cited by 2 | Viewed by 1585

Abstract

The well-defined heterostructure of the photocathode is desirable for photoelectrochemically producing hydrogen from aqueous solutions. Herein, enhanced heterostructures were fabricated based on typical stable covalent organic framework (TpPa-1) films and TiO₂ nanotube arrays (NTAs) as a proof-of-concept model to tune the photoelectrochemical (PEC) hydrogen generation by tailoring the photoelectrode microstructure and interfacial charge transport. Ultrathin TpPa-1 films were uniformly grown on the surface of TiO₂ NTAs via a solvothermal condensation of building blocks by tuning the monomer concentration. The Pt₁@TpPa-1/TiO₂-NTAs photoelectrode with single-atom Pt₁ as a co-catalyst demonstrated improved visible-light response, enhanced photoconductance, lower onset potential, and decreased Tafel slope value for hydrogen evolution. The hydrogen evolution rate of the Pt₁@TpPa-1/TiO₂-NTAs photoelectrode was five times that of Pt₁@TpPa-1 under AM 1.5 simulated sunlight irradiation and the bias voltage of 0 V. A lower overpotential was recorded as 77 mV@10 mA cm⁻² and a higher photocurrent density as 1.63 mA cm⁻². The hydrogen evolution performance of Pt₁@TpPa-1/TiO₂-NTAs photoelectrodes may benefit from the well-matched band structures, effective charge separation, lower interfacial resistance, abundant interfacial microstructural sites, and surficial hydrophilicity. This work may raise a promising way to design an efficient PEC system for hydrogen evolution by tuning well-defined heterojunctions and interfacial microstructures. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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Review

Jump to: Research

19 pages, 8355 KiB

Open AccessReview

Nonlinear Optical Properties from Engineered 2D Materials

by Jia Shi, Shifeng Feng, Peng He, Yulan Fu and Xinping Zhang

Molecules 2023, 28(18), 6737; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28186737 - 21 Sep 2023

Cited by 2 | Viewed by 1689

Abstract

Two-dimensional (2D) materials with atomic thickness, tunable light-matter interaction, and significant nonlinear susceptibility are emerging as potential candidates for new-generation optoelectronic devices. In this review, we briefly cover the recent research development of typical nonlinear optic (NLO) processes including second harmonic generation (SHG), third harmonic generation (THG), as well as two-photon photoluminescence (2PPL) of 2D materials. Nonlinear light-matter interaction in atomically thin 2D materials is important for both fundamental research and future optoelectronic devices. The NLO performance of 2D materials can be greatly modulated with methods such as carrier injection tuning, strain tuning, artificially stacking, as well as plasmonic resonant enhancement. This review will discuss various nonlinear optical processes and corresponding tuning methods and propose its potential NLO application of 2D materials. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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23 pages, 5723 KiB

Open AccessReview

Photocatalytic Applications of ReS₂-Based Heterostructures

by Nan Wang, Yashu Li, Lin Wang and Xuelian Yu

Molecules 2023, 28(6), 2627; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28062627 - 14 Mar 2023

Cited by 4 | Viewed by 2479

Abstract

ReS₂-based heterostructures, which involve the coupling of a narrow band-gap semiconductor ReS₂ with other wide band-gap semiconductors, have shown promising performance in energy conversion and environmental pollution protection in recent years. This review focuses on the preparation methods, encompassing hydrothermal, chemical vapor deposition, and exfoliation techniques, as well as achievements in correlated applications of ReS₂-based heterostructures, including type-I, type-II heterostructures, and Z-scheme heterostructures for hydrogen evolution, reduction of CO₂, and degradation of pollutants. We believe that this review provides an overview of the most recent advances to guide further research and development of ReS₂-based heterostructures for photocatalysis. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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36 pages, 8036 KiB

Open AccessReview

Recent Advances of Modified Ni (Co, Fe)-Based LDH 2D Materials for Water Splitting

by Chenguang Li, Yupeng Bao, Enzhou Liu, Binran Zhao and Tao Sun

Molecules 2023, 28(3), 1475; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28031475 - 3 Feb 2023

Cited by 13 | Viewed by 4057

Abstract

Water splitting technology is an efficient approach to produce hydrogen (H₂) as an energy carrier, which can address the problems of environmental deterioration and energy shortage well, as well as establishment of a clean and sustainable hydrogen economy powered by renewable energy sources due to the green reaction of H₂ with O₂. The efficiency of H₂ production by water splitting technology is intimately related with the reactions on the electrode. Nowadays, the efficient electrocatalysts in water splitting reactions are the precious metal-based materials, i.e., Pt/C, RuO₂, and IrO₂. Ni (Co, Fe)-based layered double hydroxides (LDH) two-dimensional (2D) materials are the typical non-precious metal-based materials in water splitting with their advantages including low cost, excellent electrocatalytic performance, and simple preparation methods. They exhibit great potential for the substitution of precious metal-based materials. This review summarizes the recent progress of Ni (Co, Fe)-based LDH 2D materials for water splitting, and mainly focuses on discussing and analyzing the different strategies for modifying LDH materials towards high electrocatalytic performance. We also discuss recent achievements, including their electronic structure, electrocatalytic performance, catalytic center, preparation process, and catalytic mechanism. Furthermore, the characterization progress in revealing the electronic structure and catalytic mechanism of LDH is highlighted in this review. Finally, we put forward some future perspectives relating to design and explore advanced LDH catalysts in water splitting. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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23 pages, 3642 KiB

Open AccessReview

Interlayer Chemical Modulation of Phase Transitions in Two-Dimensional Metal Chalcogenides

by Zhi Zhang, Yi Wang, Zelin Zhao, Weijing Song, Xiaoli Zhou and Zejun Li

Molecules 2023, 28(3), 959; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28030959 - 18 Jan 2023

Cited by 1 | Viewed by 2130

Abstract

Two-dimensional metal chalcogenides (2D-MCs) with complex interactions are usually rich in phase transition behavior, such as superconductivity, charge density wave (CDW), and magnetic transitions, which hold great promise for the exploration of exciting physical properties and functional applications. Interlayer chemical modulation, as a renewed surface modification method, presents congenital advantages to regulate the phase transitions of 2D-MCs due to its confined space, strong guest–host interactions, and local and reversible modulation without destructing the host lattice, whereby new phenomena and functionalities can be produced. Herein, recent achievements in the interlayer chemical modulation of 2D-MCs are reviewed from the aspects of superconducting transition, CDW transition, semiconductor-to-metal transition, magnetic phase transition, and lattice transition. We systematically discuss the roles of charge transfer, spin coupling, and lattice strain on the modulation of phase transitions in the guest–host architectures of 2D-MCs established by electrochemical intercalation, solution-processed intercalation, and solid-state intercalation. New physical phenomena, new insight into the mechanism of phase transitions, and derived functional applications are presented. Finally, a prospectus of the challenges and opportunities of interlayer chemical modulation for future research is pointed out. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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23 pages, 9757 KiB

Open AccessReview

Recent Advances in Surface Modifications of Elemental Two-Dimensional Materials: Structures, Properties, and Applications

by Junbo Chen, Chenhui Wang, Hao Li, Xin Xu, Jiangang Yang, Zhe Huo, Lixia Wang, Weifeng Zhang, Xudong Xiao and Yaping Ma

Molecules 2023, 28(1), 200; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28010200 - 26 Dec 2022

Cited by 7 | Viewed by 2778

Abstract

The advent of graphene opens up the research into two-dimensional (2D) materials, which are considered revolutionary materials. Due to its unique geometric structure, graphene exhibits a series of exotic physical and chemical properties. In addition, single-element-based 2D materials (Xenes) have garnered tremendous interest. At present, 16 kinds of Xenes (silicene, borophene, germanene, phosphorene, tellurene, etc.) have been explored, mainly distributed in the third, fourth, fifth, and sixth main groups. The current methods to prepare monolayers or few-layer 2D materials include epitaxy growth, mechanical exfoliation, and liquid phase exfoliation. Although two Xenes (aluminene and indiene) have not been synthesized due to the limitations of synthetic methods and the stability of Xenes, other Xenes have been successfully created via elaborate artificial design and synthesis. Focusing on elemental 2D materials, this review mainly summarizes the recently reported work about tuning the electronic, optical, mechanical, and chemical properties of Xenes via surface modifications, achieved using controllable approaches (doping, adsorption, strain, intercalation, phase transition, etc.) to broaden their applications in various fields, including spintronics, electronics, optoelectronics, superconducting, photovoltaics, sensors, catalysis, and biomedicines. These advances in the surface modification of Xenes have laid a theoretical and experimental foundation for the development of 2D materials and their practical applications in diverse fields. Full article

(This article belongs to the Special Issue Chemical Functionalization of Two-Dimensional Materials)

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