Our first-principles calculations indicate the possibility of preparing spin-polarized scanning tunneling microscopy (SP-STM) probes from Fe-doped capped carbon nanotubes (CNTs). The structural stability, magnetic moment, and electronic property of hybrid systems are found to depend on the Fe adsorption site, which is attributed to the hybridization between Fe 3d and C 2p orbitals. The CNTs with Fe atoms adsorbed at the tip-top are demonstrated to be promising candidates for the SP-STM probe, with a high spin polarization leading to a completely spin-polarized current at lower voltages. In contrast, the CNTs encapsulating Fe atom are basically nonmagnetic, and thus useless for the SP-STM probe application in nature.
Three-dimensional (3D) nitrogen-doped carbon nanotubes (N-CNTs)/Co(OH)2 core-shell nanostructures as binder-free supercapacitor electrode have been synthesized via electrodeposition and chemical vapour deposition. The ultrathin Co(OH)2 nanosheets are uniformly coated on the surface of N-CNTs. Such unique well-designed binder-free electrode exhibits a high areal capacitance (0.46 F cm−2 at a current density of 1 mA cm−2) and good cycling stability (81.2% capacitance retention after 2000 cycles). In the electrode, the cable-like N-CNTs around Ni foam with close contact act as current collector, facilitating the electrical transport, while two-dimensional Co(OH)2 nanosheets grown on external surface increase the surface area and provide good contact with ions at electrode/electrolyte interface, exhibiting low charge transfer resistance (Rct) and better charge storage performance. As a result, such combined synthetic strategy may provide design guidelines for constructing advanced binder-free supercapacitors electrode.
This review describes recent advances in two-dimensional MoS2 nanosheets and their composite materials for understanding their high-electrocatalytic performance in HER and ORR.
Abstract Despite significant advancements in the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells, improving carrier management in top cells remains challenging due to the defective dual interfaces of wide-bandgap perovskite, particularly on textured silicon surfaces. Herein, a series of halide ions (Cl − , Br − , I − ) substituted piperazinium salts are designed and synthesized as post-treatment modifiers for perovskite surfaces. Notably, piperazinium chloride induces an asymmetric bidirectional ions distribution from the top to the bottom surface, with large piperazinium cations concentrating at the perovskite surface and small chloride anions migrating downward to accumulate at the buried interface. This results in effective dual-interface defect passivation and energy band modulation, enabling wide-bandgap (1.68 eV) perovskite solar cells to achieve a PCE of 22.3% and a record product of open-circuit voltage × fill factor (84.4% relative to the Shockley–Queisser limit). Furthermore, the device retains 91.3% of its initial efficiency after 1200 h of maximum power point tracking without encapsulation. When integrated with double-textured silicon heterojunction solar cells, a remarkable PCE of 31.5% is achieved for a 1.04 cm 2 monolithic perovskite/silicon tandem solar cell, exhibiting excellent long-term operational stability ( T 80 = 755 h) without encapsulation in ambient air. This work provides a convenient strategy on dual-interface engineering for making high-efficiency and stable perovskite platforms.
Abstract Polymers prepared from ionic liquids are widely called polymerized ionic liquids (PILs). Compared to monocationic and dicationic ILs, PILs have higher molecular weights, charge, and greater intermolecular interactions, which make PILs have a higher possibility to generate better lubricity. PILs of poly‐alkylimidazolium bis(trifluoromethylsulfonyl)imide (PImC 6 NTf 2 ) is studied herein. Dicationic ILs of 1,1′‐(pentane‐1,5‐diyl)‐bis(3‐butylimidazolium) bis(trifluoromethylsulfonyl)imide (BIm 5 ‐(NTf 2 ) 2 ) is used as additive to decrease the crystallization temperature of PImC 6 NTf 2 . Lubricity of PImC 6 NTf 2 and PImC 6 NTf 2 +BIm 5 ‐(NTf 2 ) 2 , as well as BIm 5 ‐(NTf 2 ) 2 for comparison is evaluated under severe conditions, i.e., 3.0 to 3.5 GPa and 200 °C. The rheological study suggests that PImC 6 NTf 2 can be classified into grease. Tribological test results show that PImC 6 NTf 2 has much better antiwear property than BIm 5 ‐(NTf 2 ) 2 , especially at 3.5 GPa. Adding 4% BIm 5 ‐(NTf 2 ) 2 to PImC 6 NTf 2 is able to reduce friction under high pressure. At 200 °C, PImC 6 NTf 2 exhibits excellent lubricity. The mixture of 96%PImC 6 NTf 2 +4%BIm 5 ‐(NTf 2 ) 2 shows even better antiwear property than neat PImC 6 NTf 2 and exhibits the highest friction reducing property among the ILs at 200 °C. It is speculated that the robust strength of PILs and strong adhesion between PILs and solids are key factors in achieving the excellent antiwear property.
Ab initio calculations show that (5,5) and (6,6) single-walled gallium nitride nanotubes (GaN NTs) in bundles could aggregate spontaneously to form new condensed phases when bundled tubes are close enough under hydrostatic pressure. The new GaN phases have typical porous structures, constructed by alternating tetragons and hexagons around the original tube walls. Owing to the different compatibilities of the chirality of the tube with the symmetry of the array, the new phase formed from (5,5) GaN NT bundles is triclinic and that from (6,6) ones is hexagonal. These porous GaN phases possess tetrahedral bonding corresponding to sp3 hybridization, different from sp2 hybridized bonding in individual GaN NTs. The interaction between tubes not only controls the structural transformation but also influences the electronic structure of porous GaN. We expect that the two-dimensional-channeled porous structure of GaN is advantageous for the usage of GaN as the molecular sieve and as the excellent dilute magnetic semiconductor by considerable magnetic doping.
Abstract Na 2 V 6 O 16 ·3H 2 O nanobelts with lengths of 100—200 μm are hydrothermally synthesized from aqueous solutions of Na 3 VO 4 and HCl (autoclave, 200 °C, 24 h, 99% yield).
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)