A challenge in molecular electronics is to control the strength of the molecule-electrode coupling to optimize device performance. Here we show that non-covalent contacts between the active molecular component (in this case, ferrocenyl of a ferrocenyl-alkanethiol self-assembled monolayer (SAM)) and the electrodes allow for robust coupling with minimal energy broadening of the molecular level, precisely what is required to maximize the rectification ratio of a molecular diode. In contrast, strong chemisorbed contacts through the ferrocenyl result in large energy broadening, leakage currents and poor device performance. By gradually shifting the ferrocenyl from the top to the bottom of the SAM, we map the shape of the electrostatic potential profile across the molecules and we are able to control the direction of rectification by tuning the ferrocenyl-electrode coupling parameters. Our demonstrated control of the molecule-electrode coupling is important for rational design of materials that rely on charge transport across organic-inorganic interfaces.

It is proposed herein that in order to obtain ultralarge-pore ordered mesoporous silicas using surfactanttemplated synthesis with micelle expanders, one should select a micelle swelling agent with a moderate swelling ability to achieve an appreciable pore diameter enlargement while avoiding the formation of heterogeneous and/or poorly defined nanostructure. It is suggested to identify viable swelling agents based on the extent of solubilization of swelling agents in micellar solutions. On the basis of this reasoning, cyclohexane, 1,3,5-triethylbenzene and 1,3,5-triisopropylbenzene (TIPB) were selected for the synthesis of large-pore SBA-15 silicas with two-dimensional (2-D) hexagonal structures of cylindrical mesopores. SBA-15 with pore diameter tunable from 10 to 26 nm was obtained at initial synthesis temperature 12.25-20 °C using Pluronic P123 triblock copolymer as a micellar template and triisopropylbenzene as a micelle expander. Structures of the materials were characterized using small-angle X-ray scattering, TEM, and gas adsorption. The lowering of the initial synthesis temperature with adjustment of the amount of TIPB afforded pore diameters up to 26 nm (BJH pore diameters up to 34 nm) and (100) interplanar spacings up to 26 nm for 2-D hexagonal structure. As the initial synthesis temperature was lowered further, the pore diameter increased further (to ∼50 nm) with appreciable retention of cylindrical pore shape, but the pore structure became heterogeneous. The present approach makes silicas with 2D hexagonally ordered cylindrical pores of diameter up to 26 nm readily available and opens new opportunities in the synthesis of materials with other pore geometries and framework types.

Constructing a heterojunction and introducing an interfacial interaction by designing ideal structures have the inherent advantages of optimizing electronic structures and macroscopic mechanical properties. An exquisite hierarchical heterogeneous structure of bimetal sulfide Sb 2 S 3 @FeS 2 hollow nanorods embedded into a nitrogen-doped carbon matrix is fabricated by a concise two-step solvothermal method. The FeS 2 interlayer expands in situ grow on the interface of hollow Sb 2 S 3 nanorods within the nitrogen-doped graphene matrix, forming a delicate heterostructure. Such a well-designed architecture affords rapid Na + diffusion and improves charge transfer at the heterointerfaces. Meanwhile, the strongly synergistic coupling interaction among the interior Sb 2 S 3 , interlayer FeS 2 , and external nitrogen-doped carbon matrix creates a stable nanostructure, which extremely accelerates the electronic/ion transport and effectively alleviates the volume expansion upon long cyclic performance. As a result, the composite, as an anode material for sodium-ion batteries, exhibits a superior rate capability of 537.9 mAh g −1 at 10 A g −1 and excellent cyclic stability with 85.7% capacity retention after 1000 cycles at 5 A g −1 .Based on the DFT calculation, the existing constructing heterojunction in this composite can not only optimize the electronic structure to enhance the conductivity but also favor the Na 2 S adsorption energy to accelerate the reaction kinetics. The outstanding electrochemical performance sheds light on the strategy by the rational design of hierarchical heterogeneous nanostructures for energy storage applications.

Large-pore SBA-15 silicas were synthesized using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer Pluronic P123 as a template and hexane as a micelle expander. The reaction was initially carried out at 15 degrees C, followed by the heating of the synthesis gel at temperatures from 40 to 130 degrees C. Small-angle X-ray scattering data indicate that highly ordered two-dimensional hexagonal material (SBA-15 structure) formed at 15 degrees C and was preserved even after 5 days of heating at 130 degrees C. The unit-cell parameter for as-synthesized SBA-15 silicas was about 16.5 nm and increased only slightly after the heat treatment, whereas the unit-cell parameter after calcination was appreciably larger (16 vs 14 nm) for materials that were subjected to the thermal treatment. The pore size distribution of SBA-15 formed at 15 degrees C was narrow and centered at approximately 9.5 nm, which is close to the upper limit of pore diameters typically reported for SBA-15. The presence of constrictions in the pores of this material was evident. The heat treatment led to the elimination of the constrictions and to the pore diameter increase to 15 nm or more, tailored by the selection of appropriate treatment temperature and time. The pore size increase was the fastest during the first day of treatment, but it continued for at least 5 days. The pore size distribution broadened as the time of the treatment increased beyond 1 day. The pore size increase appears to be primarily related to the decrease in the degree of shrinkage during the calcination (removal of the template) and the decrease in the pore wall thickness.

SnS 2 has been extensive studied as an anode material for sodium storage owing to its high theoretical specific capacity, whereas the unsatisfied initial Coulombic efficiency (ICE) caused by the partial irreversible conversion reaction during the charge/discharge process is one of the critical issues that hamper its practical applications. Hence, heterostructured SnS 2 /Mn 2 SnS 4 /carbon nanoboxes (SMS/C NBs) have been developed by a facial wet-chemical method and utilized as the anode material of sodium ion batteries. SMS/C NBs can deliver an initial capacity of 841.2 mAh g −1 with high ICE of 90.8%, excellent rate capability (752.3, 604.7, 570.1, 546.9, 519.7, and 488.7 mAh g −1 at the current rate of 0.1, 0.5, 1.0, 2.0, 5.0, and 10.0 A g −1 , respectively), and long cycling stability (522.5 mAh g −1 at 5.0 A g −1 after 500 cycles). The existence of SnS 2 /Mn 2 SnS 4 heterojunctions can effectively stabilize the reaction products Sn and Na 2 S, greatly prevent the coarsening of nanosized Sn 0 , and enhance reversible conversion−alloying reaction, which play a key role in improving the ICE and extending the cycling performance. Moreover, the heterostructured SMS coupled with the interacting carbon network provides efficient channels for electrons and Na + diffusion, resulting in an excellent rate performance.

Regulating nanocrystal composition with multiphase compounds is considered an efficient approach to enhance electrochemical performance and structure stability. Nevertheless, the thorough understanding of significant reaction mechanisms and insight into the reason of enhanced performance is still urgent. In this work, the bimetallic sulfide Bi 2 S 3 /MoS 2 heterogeneous with abundant phase boundaries is successfully fabricated. The in situ investigation of Na + -storage mechanism confirms that enormous phase boundaries are self-generated by composition optimization and rational structural design. More importantly, the full understanding of abundant phase boundaries on the enhanced electrochemical properties is explicitly unraveled by combining theoretical analysis and experimental results. It confirms that the interior self-built-in electric-field induced by phase boundaries can enhance the reaction kinetics and boost the charge transfer. Besides, the Bi/Na 2 S interface is well-maintained by the homogeneously distributed phase boundaries, effectively improving the conversion/alloying reversibility and keeping integrity without agglomeration and pulverization. As expected, the Bi 2 S 3 / MoS 2 composite exhibits superior rate capability and long-cycling stability (323.4 mAh g −1 after long-term 1200 cycles at ultrahigh rate of 10 A g −1 ). This strategy of constructing sufficient phase boundaries sheds light on the enhancement of reversibility and stability for other advanced conversion/ alloying-type anode materials.

High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi0.88Co0.09Mn0.03O2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg−1 at 0.1 C and 25 °C.

Poly(styrenesulfonic acid)-functionalized materials based on poly(styrenesulfonic acid sodium salt) incorporated via aqueous atom transfer radical polymerization (ATRP) initiated from the surface of large-pore mesoporous SBA-15 silica support have been synthesized. The inorganic-organic nature of these hybrid materials makes them particularly desirable for acid-catalyzed reactions that require extended and hydrophobic surface areas with a narrow pore diameter distribution in the mesoporous range. Acidic hybrid materials were prepared by grafting the ATRP-initiator (3-(chlorodimethylsilyl)propyl bromoisobutyrate) on the silica surface, subsequent polymerization of the styrenesulfonic acid sodium salt monomer, and final sodium ion exchange by acid activation. Conventional and ultra-large-pore SBA-15 silica supports with nominal (BJH) pore diameter ranging from 8 to 32 nm were used for the incorporation of different polymer loadings at different polymerization times. The silylation of ATRP-initiator-functionalized SBA-15 supports has allowed a better control of the ATRP within the mesoporous structure. The use of ultra-large-pore SBA-15 supports provides a remarkable increase of the porosity which allowed us to properly allocate the polymer. The hybrid poly(styrenesulfonic acid)-modified materials showed good catalytic activities in the esterification of oleic acid with n-butanol, particularly in terms of intrinsic activity per acid site.