J. Mater. Chem. A, 2019,7, 540-548

Cite this: DOI: 10.1039/c8ta08868c

Stability is one of the major challenges of organic–inorganic hybrid perovskite materials (APbX3, where A ¼MA+, FA+ and Cs+, and X ¼ I, Br and Cl, respectively) in optoelectronic device applications. APbX3materials are extremely sensitive to temperature, humidity and oxygen. Although degradation of thematerials caused by oxygen and moisture could be partially solved by encapsulation techniques, further improving the stability of perovskites under external heat is still demanding. Generally, APbX3 would decompose into AX and PbX2 at the early stage, when it is in a high-temperature environment. In this contribution, we demonstrated that pressure can reinforce the thermal stability of MAPbX3, by promotingthe reverse reaction. The stability reinforcement of MAPbI3 by mechanical forces was found to be moreeffective compared with that of MAPbBr3/MAPbCl3. Furthermore, we carried out quantitative research tomimic pressure induced reverse reactions, through dry-grinding the powder mixtures of equimolar PbX2and AX. We found that the conversion yields and reaction paths were dramatically different dependingon the type of organic-cation (A) and halide (X). APbI3, CsPbBr3 and CsPbCl3 can be directly andcompletely synthesized by the dry grinding method, and thus they are more promising candidates formaterial recovery by external forces. Meanwhile, it was found that CsPbBr3 and CsPbCl3 crystalize via Cs4PbX6 (X ¼ Br or Cl) intermediate states. Our results provide a robust strategy for the specific design ofperovskite material based optoelectronic devices, especially for applications demanding better stability.

作者：Hu, X.;  Chen, F.;  Zhang, Z.;  Wang, S.;  Liang, J.;  Shi, Y.;  Su, C.-Y.;  Ru, Q.;  He, Q.;  Hou, X.; Chu, B

发表杂志：Materials Letters 卷 233 页 332-335

Abstract

The NaF dual-ion battery was demonstrated as potential battery where fluoride and sodium ions were extracted from NaF electrolyte respectively during discharging; while the charging process causes the release of ions to the electrolyte. However, previous studies reveal that electrode configuration with large-sized particles will significantly reduce the energy density and stability. Herein, we proposed a novel hybridelectrode assembly of bismuth nanoparticles/carbon nanotubes (nano-Bi@CNTs), which could achieve theexcellent electrochemical stability. The new NaF dual-ion battery, consisting of nano-Bi@CNTs-Na0.44MnO2 (NMO), demonstrates a high specific capacity of 109.5 mAh/g after 80 cycles with 100 mA/g current density. Moreover, the electrochemical mechanism of fluoride ion in this system was comprehensively investigated. The current research is significant for the novel anion energy storage system. (C) 2018 Elsevier B.V. All rights reserved.

作者：Huang, S.;  Liu, L.;  Zheng, Y.;  Wang, Y.;  Kong, D.;  Zhang, Y.;  Shi, Y.;  Zhang, L*.;  Schmidt, O. G.; Yang, H. Y*

发表杂志：Advanced Materials

Abstract

Alloying-type materials are promising anodes for high-performance sodium-ion batteries (SIBs) because of their high capacities and low Na-ion insertion potentials. However, the typical candidates, such as P, Sn, Sb, and Pb, suffer from severe volume changes (approximate to 293-487%) during the electrochemical reactions, leading to inferior cycling performances. Here, a high-rate and ultrastable alloying-type anode based on the rolled-up amorphous Si nanomembranes is demonstrated. The rolled-up amorphous Si nanomembranesshow a very small volume change during the sodiation/desodiation processes and deliver an excellent rate capability and ultralong cycle life up to 2000 cycles with 85% capacity retention. The structural evolution and pseudocapacitance contribution are investigated by using the ex situ characterization techniques combined with kinetics analysis. Furthermore, the mechanism of efficient sodium-ion storage in amorphous Si is kinetically analyzed through an illustrative atomic structure with dangling bonds, offering a new perspective on understanding the sodium storage behavior. These results suggest that nanostructured amorphous Si is a promising anode material for high-performance SIBs.

作者：Li, H.;  Li, Y.;  Aljarb, A.;  Shi, Y.; Li, L.-J

发表杂志：Chemical Reviews 卷 118 期 13 页6134-6150

Abstract

Recently there have been many research breakthroughs in two-dimensional (2D) materials including graphene, boron nitride (h-BN), black phosphors (BPs), and transition-metal dichalcogenides (TMDCs). The unique electrical, optical, and thermal properties in 2D materials are associated with their strictly defined low dimensionalities. These materials provide a wide range of basic building blocks for next generation electronics. The chemical vapor deposition (CVD) technique has shown great promise to generate high-quality TMDC layers with scalable size, controllable thickness, and excellent electronic properties suitable for both technological applications and fundamental sciences. The capability to precisely engineer 2D materials by chemical approaches has also given rise to fascinating new physics, which could lead to exciting new applications. In this Review, we introduce the latest development of TMDC synthesis by CVD approaches and provide further insight for the controllable and reliable synthesis of atomically thin TMDCs. Understanding ofthe vapor-phase growth mechanism of 2D TMDCs could benefit the formation of complicated heterostructures and novel artificial 2D lattices.

作者：Li, H.;  Shi, Y*.; Li, L.-J*

发表杂志：Carbon 卷 127 页 602-610

Abstract

Being a representative candidate from the two-dimensional (2D) materials family, graphene has been one ofthe most intensively researched candidates because of its ultrahigh carrier mobility, quantum Hall effects, excellent mechanical property and high optical transmittance. Unfortunately, the lack of a band gap makes graphene a poor fit for digital electronics, where the current on/off ratio is critical. Huge efforts have been advocated to discover new 2D layered materials with wonderful properties, which complements the needs of2D electronics. Appropriately designed graphene based hybrid structure could perform better than its counterpart alone. The graphene hybrid structure soon become one of the most exciting frontiers in advanced 2D materials, and many efforts have been made to create artificial heterostructures by assembling of graphene with various layered materials. In this review, we present the recent development in synthesisand applications of graphene based 2D heterostructures. Although 2D transition metal dichalcogenide semiconductors have been demonstrated as strong candidates for next-generation electronics and optoelectronics, by combining advantages of various properties of 2D materials together with graphene, it is highly possible to build entire digital circuits using atomically thin components, and create many novel devices that can be utilized in different areas. 

作者：Li, Z.;  Li, J.;  Ding, D.;  Yao, H.;  Liu, L.;  Gong, X.;  Tian, B.;  Li, H.;  Su, C.; Shi, Y*

发表杂志：ACS Applied Material & Interfaces 卷 10 期 42 页 36493-36504

Abstract

Lead trihalide perovskites have been integrated with atomically thin WS2 and served as absorption layers to improve photoresponsivity in photodetectors. The combination of perovskites and two-dimensional (2D) transition-metal dichalcogenide (TMDC) materials provides the platform to study light-matter interactions and charge transfer mechanisms in optoelectronic devices. Herein, conductive and photoconductive atomic force microscopy were used to image the dark current and photocurrent generated in WS2/CH3NH3PbI3 (MAPbI(3)) heterostructures. Dark current measurement in the applied voltage range displays characteristic diode behavior, which can be well described by thermionic emission theory. Under laser illumination at 532 nm, the spatially resolved photocurrent images exhibit location-dependent photoresponse, where the photocurrent increases remarkably for the WS2/MAPbI(3) heterostructures compared with the bare MAPbI(3) regions. Furthermore, comparative surface roughness and 2D Fourier analysis of the topographic and current maps reveal that the interfacial conditions of the WS2/MAPbI(3) heterojunctions play an important role in the charge separation process. In addition, WS2/MAPbI(3)-based photodetectors have been fabricated. Our study provides direct evidence that atomically thin TMDC monolayers can effectively assist the charge separation process and improve the light-to-electric energy conversion, which aids in the design principles and understanding of 2D heterostructured optoelectronic devices.

作者：Liang, Q.;  Chen, F*.;  Wang, S.;  Ru, Q.;  He, Q.;  Hou, X.;  Su, C.-y.; Shi, Y*

发表杂志：Energy Storage Materials

Abstract

Renewable energy-related technologies have become more important due to the increasing energy consumption. Herein, we put forward a novel organic flow desalination battery (ORFDB) using redox-active organic molecule electrolyte materials dissolved in the aqueous sodium chloride feed. Riboflavin-5’-phosphate sodium salt dihydrate (FMN-Na) is used as the anolyte, and the catholyte is 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO). Sodium and chloride ions in salt feed were moved respectively to anolyte and catholyte by electrochemical reaction of electrolytes during the charge process, and return to the feed during the discharge process. This ORFDB system possesses the stable stability up to fifty cycles and the excellent rate performance. This ORFDB exhibits the cost-effective renewable energy storageand the possibility of salt removal based on the electrochemistry of organic molecules.

作者：Lim, Y. V.;  Huang, S.;  Zhang, Y.;  Kong, D.;  Wang, Y.;  Guo, L.;  Zhang, J.;  Shi, Y.;  Chen, T. P.;  Ang, L. K.; Yang, H. Y

发表杂志：Energy Storage Materials 卷 15 页 98-107

Abstract

Transition metal phosphides, such as iron phosphide (FeP), have recently been studied as promising high performance active materials for sodium-ion batteries (SIBs) and hydrogen evolution reaction (HER) due to their excellent energy storage and conversion capabilities. To achieve long cycle lifetime, high rate sodium storage performance and stable HER reactivity, porous FeP/C nanostructures have been designed and synthesized through low temperature phosphorization of the Metal-Organic Framework (MOF) nanostructure. The resulting FeP/C composite consists of highly porous nanocubic structure with FeP nanoparticles distributing the carbon scaffolding, showing high surface area and small pore size distribution. This unique nanostructure enables fast and efficient electrons/ions transportation, and provides abundant reactive sites uniformly distributing the highly-ordered MOF-derived nanocubes. Benefitting from the unique porous structure, the FeP/C nanocubes exhibit remarkable sodium storage performance in terms of high capacity (410 mA h g−1, 100 mA g−1), excellent rate capacity (up to 1 A g−1) and long cycle life (> 200 cycles). The electrochemical reaction mechanisms of the FeP/C composite upon sodiation/desodiation are investigated in detail via ex-situXRD, SEM and TEM methods, which show that the sodium storage in FeP is based on both the intercalation/conversion reactions. In addition, FeP/C as HER electrodes maintain its reactivity for at least 40 h and exhibit an low onset overpotential of 80 mV and a low Tafel slope of 40 mV dec−1. These results reveal the sodium storage mechanism of FeP and suggest that the MOF-derived FeP/C composite is a promising candidate for high-performance SIBs and HER electrode material.

作者：Liu, L.;  Yao, H.;  Li, H.;  Wang, Z.; Shi, Y

发表杂志：FlatChem 卷10 页 22-38

Abstract

Recent advances in the development of low-dimensional materials such as two-dimensional transition-metal dichalcogenides (2D TMDCs) and metal halide perovskites have attracted a lot of attention. These low-dimensional materials have been shown properties suited for photonics and optoelectronics applications, opening up new possibilities for micro/nano lasing applications. In this article, we review 2D TMDCs and perovskites as gain mediums in micro/nano lasers. First, we give a brief introduction about the principles of lasing. Second, the micro/nano lasers by using 2D TMDCs as gain medium are discussed. Third, the micro/nano lasers by using perovskites as gain medium are summarized. The lasing characteristics such as cavity types, emission wavelengths, coherence properties and lasing thresholds are compared and discussed to show the pros and cons of these two kinds of materials. The future perspectives for the development of micro/nano lasers based on these two materials are discussed.

作者：Wang, Y.;  Kong, D.;  Huang, S.;  Shi, Y.;  Ding, M.;  Lim, Y. V.;  Xu, T.;  Chen, F.;  Li, X.; Yang, H. Y*.

发表杂志：Journal of Materials Chemistry A 卷 6 期 23 页 10813-10824

Abstract

Sodium ion batteries (SIBs) are proposed as alternatives to the current widely used lithium ionbatteries (LIBs) due to the abundance of battery-grade sodium sources in nature. However, the search for suitable high-performance electrode materials for SIBs continues to remain a significant challenge. Herein, we report a hybrid nanoarchitecture with nitrogen-doped graphene quantum dots (NGQDs)-decorated WS2 nanosheets anchored on a porous three-dimensional carbon foam (NGQDs-WS2/3DCF) scaffold as the anode that enables long-term cycling and high rate capability for SIBs. Benefiting from the 3D robust porous interpenetrating framework and the NGQDs decoration, the NGQDs-WS2/3DCF nanoarchitecture exhibits a high rate capability with a capacity of 268.4 mA h g(-1) at 2000 mA g(-1), and a long lifetime with an extraordinary capacity retention of 97.1% over 1000 cycles. Furthermore, the pseudocapacitance contributions of the NGQDs-WS2/3DCF nanoarchitecture are quantified by an in-depth kinetics analysis, which provides a better understanding of the excellent electrochemical performances. Remarkably, a cable-shaped flexiblefull SIB was also demonstrated using NGQDs-WS2/ 3DCF as the anode electrode, which exhibits high capacity and excellent flexibility. The nanoarchitecture fabrication approach and the surface engineering strategy as well as the demonstrated cable-shaped configuration may open an avenue for the development of wearable SIBs with high performance.

作者：Yao, H.;  Liu, L.;  Wang, Z.;  Li, H.;  Chen, L.;  Pam, M. E.;  Chen, W.;  Yang, H. Y.;  Zhang, W.; Shi, Y

发表杂志：Nanoscale 卷 10 期 13 页 6105-6112

Abstract

Tungsten disulfide monolayers have attracted extensive attention in nanoelectronics and optoelectronics applications due to their remarkable electronic and optical properties. High-quality WS2 monolayers with a scalable size and uniform thickness can be synthesized by a chemical vapor deposition method (CVD). However, they commonly contain intrinsic structural defects and different populations of charge carriers, which are responsible for different contributions of excitons, trions, and biexcitons to their photoluminescence (PL) emission. Here, we adopt sodium sulphide (Na2S) solution to chemically treat CVDgrown WS2 monolayers by a simple immersing method. The results show that WS2 monolayers have a significantly enhanced PL emission by a factor of 25-fold and an obvious red-shift of the PL wavelength, resulting from the different excitonic states induced by effective n-type doping after Na2S treatment. This work provides a simple but promising chemical doping route to significantly improve the optical properties of WS2 monolayers and paves the way for the realization of practical WS2 monolayer based optoelectronic applications.

作者：Zhang, Y.;  Lim, Y. V.;  Huang, S.;  Pam, M. E.;  Wang, Y.;  Ang, L. K.;  Shi, Y.; Yang, H. Y.

发表杂志：Small 卷 14 期 28

Abstract

In this contribution, a novel sulfate-ion-controlled synthesis is developed to fabricate freestanding nickel hydroxide nanoarrays on Ni substrate. As an inorganic morphology-controlled agent, SO42- ions play a critical role in controlling the crystal growth and the nanoarray morphologies, bymodulating the growth rate of adsorbed crystal facets or inserting into the metal hydroxide interlayers. By controlling the SO42- concentration, the nanostructured arrays are tailored from one-dimensional (1D) Ni(SO4)(0.3)(OH)(1.4) nanobelt arrays to hierarchical beta-Ni(OH)(2) nanosheet arrays. With further graphene oxide modification and postheat treatment, the obtained NiO/graphene hybrid nanoarrays show great potential for high-performance sodium-ion batteries, which exhibit a cyclability of 380 mAh g(-1) after undergoing 100 cycles at 0.5 C and reach a rate capability of 335 mA h g(-1) at 10 C.

作者：Zhou, X.;  Lin, S.-H.;  Yang, X.;  Li, H.;  Hedhili, M. N.;  Li, L.-J.;  Zhang, W*.; Shi, Y*

发表杂志：Nanoscale 卷 10 期 7 页 3444-3450

Abstract

Recent experimental and theoretical studies have demonstrated that two-dimensional (2D) transition metal dichalcogenide (TMDC) nanoflakes are one of the most promising candidates for non-noblemetal electrocatalysts for hydrogen evolution reaction (HER). However, it is still challenging to optimize their conductivity and enrich active sites for highly efficient electrochemical performance. Herein, we report a chemical vapor deposition (CVD) and thermal annealing two-step strategy to controllably synthesize hybrid electrocatalysts consisting of metallic NbS2 nanoflake backbones and a highly catalytic active MoSx nanocrystalline shell on polished commercial glass carbon (GC). In addition, the amount of MoSx in the hybrids can be easily adjusted. We first demonstrate that a small amount of MoSx significantly promotes the HER activity of 2D NbS2 nanoflakes, which is in good agreement with the density functional theory (DFT) calculation results. Moreover, the optimized MoSx@NbS2/GC electrocatalyst displays superior HER activity with overpotential of -164 mV at -10 mA cm(-2), a small Tafel slope of 43.2 mV dec(-1), and prominent electrochemical stability. This study provides a new path for enhancing the HER performance of 2D TMDC nanoflakes.