Search

Because of its excellent thermal, mechanical, and electrical properties, graphene has been used in a variety of functional coatings. Noncovalent bond functionalization and covalent bond functionalization are the most common graphene surface functionalization methods. Polymer modification, for example, can be used to give graphene and its derivatives new structure, morphology, and properties. The basic structure and predictive control principle of neural networks are discussed in this study, and a high thermal resistance porous graphene structure is reversely designed using machine learning. The effect of a graphene defect modification prediction model based on a GA (genetic algorithm) and improved BPNN (BP neural network) algorithm is investigated. The RMSE predicted by submodels 1–4 decreases by 13.26%, 3.86%, 11.71%, and 19.63%, respectively, according to the simulation results. The BPNN graphene defect modification prediction model optimized by GA has a better training and prediction effect than before optimization.

A new vapochromic, proton-conductive Pt(II) complex, [PtBr(tpypyH)]Br2 ([1Br-H]Br, tpypy = 2,2′: 6′,2′′-terpyridine-4′,4′′′-pyridine) was synthesized to improve the proton conductivity and thermal ...

Two-dimensional covalent organic frameworks (2D COFs) have attracted much attentions in proton conduction, owing to their regular pore channels and easy functionalization. However, most of COFs required the loading of proton carriers to achieve high proton conductivity. Here, we report the immobilization of flexible sulfonic acid groups on the channel walls of PyTTA-DHTA-COF (synthesized by condensation of 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetraaniline and 2,5-dihydroxyterephthalaldehyde) via a simple post-synthetic modification strategy. The sulfonated COF showed intrinsic proton conductivity up to 10^-3 at 25 °C and 100% relative humidity (RH), and high conductivity up to 10^-2 S cm^-1 under at 70 °C and 100% RH without introduction of any non-covalent acid molecules or imidazole derivatives.

Along with the rapid development of economic integration and regional economization worldwide, the growth of green and sustainable resources has posed a major concern. Proton-exchange membrane fuel cells (PEMFCs) are examples of green, resource-conserving, and environmentally protective energy resources. Porous organic polymers (POPs), a new class of porous materials with high porosity, permanent pores, excellent stability, and easily modified functional units, can offer a good platform as proton-conducting electrolytes for fuel cells. However, a simple and general design to construct POPs with high proton conductivity presents a challenging project. For this study, we used simple benzene and aromatic benzene as building units through a facile and cost-effective process to create a series of POPs. We further prepared sulfonated POPs (S-POPs) with high-density sulfonic acid groups via post-sulphonation. The S-POPs displayed excellent proton conductivity up to 10−2 S cm−1 at 25 °C and 95% relative humidity (RH), and high conductivity up to 10−1 S cm−1 at 80 °C and 95% RH, which ranked top among the most proton-conducting POPs. These results suggest that construction of S-POPs offers a simple and universal way to evolve structural designs for high proton-conductive materials.

All-solid-state lithium ion batteries (ASSLBs) are considered next-generation devices for energy storage due to their advantages in safety and potentially high energy density. As the key component in ASSLBs, solid-state electrolytes (SSEs) with non-flammability and good adaptability to lithium metal anodes have attracted extensive attention in recent years. Among the current SSEs, composite solid-state electrolytes (CSSEs) with multiple phases have greater flexibility to customize and combine the advantages of single-phase electrolytes, which have been widely investigated recently and regarded as promising candidates for commercial ASSLBs. Based on existing investigations, herein, we present a comprehensive overview of the recent developments in CSSEs. Initially, we introduce the historical development from solid-state ionic conductors to CSSEs, and then summarize the fundamentals including mechanisms of lithium ion transport, key evaluation parameters, design principles, and key materials. Four main types of advanced structures for CSSEs are classified and highlighted according to the recent progress. Moreover, advanced characterization and computational simulation techniques including machine learning are reviewed for the first time, and the main challenges and perspectives of CSSEs are also provided for their future development.

Covalent organic frameworks (COFs) are a novel class of crystalline porous polymers, which possessed high porosity, excellent stability, and regular nanochannels. Two-dimensional (2D) COFs provided 1D nanochannel to form the proton transport channels. The abovementioned features afforded a powerful potential platform for designing materials as proton transportation carriers. Herein, we incorporated sulfonic acid groups on the pore walls as proton sources for enhancing proton transport conductivity in the 1D channel. Interestingly, the sulfonic acid COFs (S-COFs) electrolytes with binder free exhibited excellent proton conductivity about 1.5 × 10^-2 S cm^-1 at 25 ℃ and 95% relative humidity (RH), which ranked the excellent performance in standard proton-conducting electrolytes. The S-COFs electrolytes kept the high proton conduction over the 24 h. The activation energy was estimated to be as low as 0.17 eV, which was much lower than most reported COFs. This research opens a new window to evolve great potential of structural design for COFs as the high proton-conducting electrolytes.

NiCo2O4 microrods with open structures are successfully synthesized using a solvothermal method. Compared with those of dense microspheres, the one-dimensional (1D) porous microrods show much higher capacities and stability for both Li- and Na-ion batteries due to the 1D open structure facilitating fast ion transport and buffering volumetric change during charge/discharge. This work demonstrates that the electrochemical performance of NiCo2O4 is highly dependent on morphologies of the active material.

Rational and precise control of the structure and dimension of electrode materials is an efficient way to improve their electrochemical performance. In this work, solvothermal or co-precipitation method is used to synthesize lithium-rich layered oxide materials of Li1.2Mn0.56Co0.12Ni0.12O2 (LLO) with various morphologies and structures, including microspheres, microrods, nanoplates, and irregular nanoparticles. These materials exhibit strong structure-dependent electrochemical properties. The porous hierarchical structured LLO microrods exhibit the best performance, delivering a discharge capacity of 264.6 mAh g−1 at 0.5 C with over 91% retention after 100 cycles. At a high rate of 5 C, a high discharge capacity of 173.6 mAh g−1 can be achieved. This work reveals the relationship between the morphologies and electrochemical properties of LLO cathode materials, and provides a feasible approach to fabricating robust and high-performance electrode materials for lithium-ion batteries.

We report a novel hollow porous hierarchical-architectured 0.5Li2MnO3·0.5LiMn0.4Co0.3Ni0.3O2 (LLO) for lithium-ion batteries (LIBs). The obtained lithium-rich layered oxides possess a large inner cavity, a permeable porous shell, and excellent structural robustness. In LIBs, such unique features are favorable for fast Li+ transportation and can provide sufficient contact between active materials and electrolytes, accommodate more Li+, and improve the kinetics of the electrochemical reaction. The as-prepared LLO displays an extremely high initial discharge capacity (296.5 mAh g–1 at 0.2 C), high rate capability (162.6 mAh g–1 at 10 C), and excellent cycling stability (237.6 mAh g–1 after 100 cycles at 0.5 C and 153.8 mAh g–1 after 200 cycles at 10 C). These values are superior to most literature data.

In this work, we report on the synthesis and characterization of nanoporous bimetallic metal-organic frameworks (FeCo-BDC). Effects of synthesis time and temperature on the structures, morphology, and catalytic performance of FeCo-BDC were investigated. Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) were used to reveal the morphological and textural characteristics. The crystal structure and chemical composition of FeCo-BDC were determined by means of X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) measurements. Interestingly, FeCo-BDC grew into the same crystal structure with different morphology in the temperature of 110–150 °C with 12–48 h. The heterogeneous catalytic activity of FeCo-BDC was tested to activate peroxydisulfate (PDS) and peroxymonosulfate (PMS) for removal of methylene blue (MB). The results found that FeCo-BDC synthesized at 150 °C with 24 h exhibited the best catalytic performance for PMS and obtained 100% of MB removal within 15 min. The abundant unsaturated metal active sites of Fe(II) and Co(II) in the skeleton of FeCo-BDC made a great contribution to the generation of sulfate ( ) and hydroxyl radicals ( OH), which resulted in the excellent performance for MB degradation.

NiCo

Efficient molybdenum(VI) modified Zr-MOF catalysts have been successfully prepared for the epoxidation of olefins. The stable and porous Zr-MOF (UiO-66(NH2)) was modified with salicylaldehyde, pyridine-2-aldehyde, or 2-pyridine chloride by the post-synthesis modification (PSM) method, and then the Mo-based catalyst was loaded by a chelating method. The MOFs not only act as the carriers of the Mo(VI) catalyst, but also improve the contacting ability between the substrate and the active center of the Mo(VI) compound. The high dispersion of the Mo catalyst on Zr-MOF and the big pore size of MOF guarantee sufficient contact between substrate and catalytic active center, thus accelerating the rate of reaction and providing improved catalytic efficiency for the epoxidation of olefins. The obtained Zr-MOF catalyst exhibited high activity for the epoxidation of olefins with 70 wt% tert-butyl hydroperoxide (TBHP) or 30% H2O2 as the oxygen sources. Furthermore, MoO2(acac)2 loaded Zr-MOF was prepared in the same way, and it also showed good catalytic performance for the epoxidation of olefins.

The electrochemical synthesis of ammonia via N2 reduction reaction (NRR) has received much attention in recent years due to its promising advantages of being more environmentally friendly and less energy consuming than conventional chemical synthesis. However, as the theoretical potentials of hydrogen evolution reaction (HER) and NRR are very close on most catalysts, H2 is the dominant product due to the much faster reaction kinetics of HER, leading to low NRR Faradaic efficiency and ammonia formation rate. The DFT calculation indicates that the transition metal nitrides, such as VN, CrN, and ZrN, are promising candidates for NRR electrocatalysts.1-2 In this study, chromium oxynitride (CrO0.66N0.56) was synthesized and its NRR performance was evaluated in a proton exchange membrane electrolyzer (PEMEL) under ambient conditions. The schematic illustration of the PEMEL employed in this study is shown in Figure 1a. The highest ammonia formation rate of 8.9×10-11 mol s-1 cm-2 and Faradic efficiency of 6.7% were achieved, shown in Figure 1b, which is so far the best result reported among the non-noble metal-based electrocatalysts under similar conditions. Its performance is even higher than that of Pt/C and Pd/C. Figure 1. a) The schematic illustration of the PEMEL device for the electrochemical synthesis of ammonia. b) The ammonia production rate and faradaic efficiency of chromium oxynitride at various potentials in a PEMEL device with ammonia water pretreated under room conditions. References (1) Abghoui, Y.; Skulason, E., J. Phys. Chem. C 2017, 121, 6141-6151. (2) Abghoui, Y.; Garden, A. L.; Hlynsson, V. F.; Björgvinsdóttir, S.; Ólafsdóttir, H.; Skúlason, E., Phys. Chem. Chem. Phys. 2015, 17, 4909-4918. Figure 1

Binary metal oxide NiCo2O4 is a promising anode material for future Li-ion batteries (LIBs) and Na-ion batteries (SIBs) owing to its inherited characteristics of high theoretical capacity and low cost.1,2 In particular, NiCo2O4 possesses high electrical conductivity, reversible capacity and mechanical stability than single-component metal oxides NiO and Co3O4. 3,4 However, the large volume change and sluggish kinetics during the charge/discharge process result in a short cycling life and poor rate performance, which limits its practical application.5 The electrochemical performance of an active material highly depends on its structure (both primary and secondary structures).6 Therefore, tailored architecture design and surface engineering of NiCo2O4 are highly desirable to secure both the high transport kinetics and sustain the structure integrity for high rate and long life. In this study, one-dimensional (1D) porous NiCo2O4 microrods and microspheres are successfully synthesized by a simple solvothermal method using different solvents followed by calcination. The solvothermal process and solvents employed in the synthesis play crucial role in determining the final morphologies of NiCo2O4. Compared with NiCo2O4 microspheres, the porous microrods exhibit much better Li- and Na-ion storage properties owing to the 1D geometry to facilitate fast ion transport and the porous structure to accommodate volume expansion of NiCo2O4 during ion insertion. The porous NiCo2O4 microrods display high initial charge capacity (1046.1 mAh g-1 at 100 mA g-1), long cycling stability (719 mAh g-1 after 600 cycles at 500 mA g-1), and rate capability for lithium-ion batteries. They also show better performance in sodium-ion batteries. This work may provide a facile way for fabricating novel structured metal oxide anode materials for batteries. Figure 1. (Left) SEM images of the 1D porous NiCo2O4 microrods and microspheres for LIBs and SIBs respectively. (Right) Rate performances at various current densities of LIBs and SIBs. References Zheng, F. C.; Zhu, D. Q.; Chen, Q. W. ACS Applied Materials & Interfaces 2014, 6, (12), 9256-9264. Lee, Y.; Kim, M. G.; Cho, J. Nano letters 2008, 8, (3), 957-961. Li, B.; Feng, J.; Qian, Y.; Xiong, S. Journal of Materials Chemistry A 2015, 3, (19), 10336-10344. Jadhav, H. S.; Kalubarme, R. S.; Park, C. N.; Kim, J.; Park, C. J. Nanoscale 2014, 6, (17), 10071-10076. Chen, J.; Ru, Q.; Mo, Y.; Hu, S. RSC Advances 2015, 5, (90), 73783-73792. Ye, J.; Liu, W.; Cai, J.; Chen, S.; Zhao, X.; Zhou, H.; Qi, L. Journal of the American Chemical Society 2010, 133, (4), 933-940. Figure 1

High energy and power densities are required for lithium-ion batteries (LIBs) for electric vehicle (EV) applications.1, 2 To meet the above mentioned requirements, silicon (Si), as an alloy-type material, has attracted great attention due to its extremely high theoretical gravimetric capacity (~4200 mAh g-1), relative low discharging potential (0.2 V versus Li/Li+), environmental friendliness, and natural abundance.3, 4 However, Si-based anodes undergo a huge volume variation upon lithiation and delithiation (~400%) that would lead to pulverization of active materials, loss of electrical contact, unstable electrolyte interphase on silicon surface and consequently, capacity fading.5 Previous studies have revealed that poly(vinylidene fluoride) (PVDF), the most common binder in making the electrode, is not good enough for Si-based anode due to its very weak wan der Waals interaction with Si.6, 7 Other functionalized binders are highly demended to improve the perforance and stability of Si-based electrodes. In this study, polyaniline (PANI) based conductive binder were developed by in-situ polymerization in acidic solution at ~ 0 oC in the presence of poly(acrylic acid) (PAA). The structure of obtained composites were characterized by Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. Si nanoparticles and PANI/PVA composite were mixed together in a weight ratio of 6:4. The electrode was fabricated by coating the mixture onto a copper foil (current collector) and dried under vacuum at 100 oC for 10 h. To measure the electrochemical performance, coin cells were assembled inside an Ar-filled glove box by using a lithium-metal plate as the counter and reference electrode, microporous polypropylene as the separator and 1 M LiPF6in ethylene carbonate (EC)–diethyl carbonate (DEC) solvent (1:1 v/v) with FEC additives as electrolyte. The assembled coin cells were activated at a current density of 200 mA/g and cycled at a current density of 4000 mA/g (1 C). The electrode showed a stable cycle performance for 100 cycles at a current density of 1 C (Figure 1a). This great improvement can be attributed to the enhanced strain compatibility (Figure 1b), great adhesive property and high elasticity of this novel binder. References Midilli, A.; Dincer, I.; Ay M. Energy Policy 2006, 34, (18), 3623-3633. Armand, M.; Tarascon, J. M. Nature 2008, 451, (7179), 652-657. Chan, C. K.; Peng, H.; Liu, G.; McIlwrath, K.; Zhang, X. F.; Huggins, R. A.; Cui, Y. Nature nanotechnology 2008, 3, (1), 31-35. Reece, S. Y.; Hamel, J. A.; Sung, K.; Jarvi, T. D.; Esswein, A. J.; Pijpers, J. J.; Nocera, D. G. Science 2011, 334, (6056), 645-648. Wu, H.; Cui, Y. Nano Today 2012, 7, (5), 414-429. Su, X.; Wu, Q.; Li, J.; Xiao, X.; Lott, A.; Lu, W.; Sheldon W. B.; Wu, J. Advanced Energy Materials 2014, 4, (1). Erk, C.; Brezesinski, T.; Sommer, H.; Schneider, R.; Janek, J. ACS applied materials & interfaces 2013, 5, (15), 7299-7307. Figure 1. (a) Cycle performance of silicon nano-particles using PANI based conductive polymer composites as binder. (b) Illustration of a possible reason why conductive binder can improve the cycle performance of silicon. Figure 1