Bi_(3.25)La_(0.75)Ti_3O_(12)纳米材料的水热合成研究

以分析纯硝酸铋、硝酸镧、钛酸四丁酯为原料,采用水热法制备了Bi3.25La0.75Ti3O12(BLT)纳米材料。用XRD和SEM对样品的物相和形貌进行了表征。讨论了矿化剂(NaOH)浓度和水热反应时间对BLT物相的影响。表明合成产物为正交相钙钛矿结构Bi3.25La0.75Ti3O12纳米片,厚度约10 nm,平均边缘尺寸约100 nm。当反应温度为200℃时,反应时间在12 h到48 h,矿化剂浓度在1 mol/L到2 mol/L范围内能有效合成Bi3.25La0.75Ti3O12。     

2D Thin Nanoflakes Assembled on Mesoporous Carbon Nanorods for Enhancing Electrocatalysis and for Improving Asymmetric Supercapacitors

Carbon nanomaterials are of great interest as the advanced supports of electrochemical active materials to enhance their performances, however, little knowledge has been put into understanding whether the pores of carbon nanomaterials as supports can tune the performance of energy storage and conversion devices due to the lack of methods for making porous carbon nanomaterials. Herein, this study demonstrates the use of 1D ordered mesoporous carbon nanorods (OMCRs) with high surface area as a new class of supports for 2D ultrathin MoS₂ and MnO₂ nanoplates to create the interesting hierarchical nanohybrids (MoS₂@OMCRs and MnO₂@OMCRs), respectively. With the significant role of OMCRs in optimizing the electron and charge transportation, MoS₂@OMCRs exhibits remarkable activity for catalyzing hydrogen evolution reaction with a low onset overpotential of 105 mV and low Tafel slope of 40 mV dec^?1, much better than those of MoS₂@ carbon nanofibers. Significantly, the asymmetric supercapacitor based on MnO₂@OMCRs as anode and OMCRS as cathode displays a maximum specific capacitance up to 100 F g^?1 at 0.2 A g^?1 and a high energy density of 55.2 W h kg^?1 at the power density of 200 W kg^?1 within a wide operating voltage of 2.0 V. The present work highlights the important role of the mesoporous carbon support in achieving the advanced energy storage and conversion.     

Tungsten diselenide nanoplates as advanced lithium/sodium ion electrode materials with different storage mechanisms

Transition-metal dichalcogenides (TMDs) exhibit immense potential as lithium/sodium-ion electrode materials owing to their sandwich-like layered structures.To optimize their lithium/sodium-storage performance,two issues should be addressed:fundamentally understanding the chemical reaction occurring in TMD electrodes and developing novel TMDs.In this study,WSe2 hexagonal nanoplates were synthesized as lithium/sodium-ion battery (LIB/SIB) electrode materials.For LIBs,the WSe2-nanoplate electrodes achieved a stable reversible capacity and a high rate capability,as well as an ultralong cycle life of up to 1,500 cycles at 1,000 mA·g-1.Most importantly,in situ Raman spectroscopy,ex situ X-ray diffraction (XRD),transmission electron microscopy,and electrochemical impedance spectroscopy measurements performed during the discharge-charge process clearly verified the reversible conversion mechanism,which can be summarized as follows:WSe2 + 4Li+ + 4e-←→ W + 2Li2Se.The WSe2 nanoplates also exhibited excellent cycling performance and a high rate capability as SIB electrodes.Ex situ XRD and Raman spectroscopy results demonstrate that WSe2 reacted with Na+ more easily and thoroughly than with Li+ and converted to Na2Se and tungsten in the 1st sodiated state.The subsequent charging reaction can be expressed as Na2Se → Se + 2Na+ + 2e-,which differs from the traditional conversion mechanism for LIBs.To our knowledge,this is the first systematic exploration of the lithium/sodium-storage performance of WSe2 and the mechanism involved.     

Defects and Interfaces on PtPb Nanoplates Boost Fuel Cell Electrocatalysis

Nanostructured Pt is the most efficient single‐metal catalyst for fuel cell technology. Great efforts have been devoted to optimizing the Pt‐based alloy nanocrystals with desired structure, composition, and shape for boosting the electrocatalytic activity. However, these well‐known controls still show the limited ability in maximizing the Pt utilization efficiency for achieving more efficient fuel cell catalysis. Herein, a new strategy for maximizing the fuel cell catalysis by controlling/tuning the defects and interfaces of PtPb nanoplates using ion irradiation technique is reported. The defects and interfaces on PtPb nanoplates, controlled by the fluence of incident C⁺ ions, make them exhibit the volcano‐like electrocatalytic activity for methanol oxidation reaction (MOR), ethanol oxidation reaction (EOR), and oxygen reduction reaction (ORR) as a function of ion irradiation fluence. The optimized PtPb nanoplates with the mixed structure of dislocations, subgrain boundaries, and small amorphous domains are the most active for MOR, EOR, and ORR. They can also maintain high catalytic stability in acid solution. This work highlights the impact and significance of inducing/controlling the defects and interfaces on Pt‐based nanocrystals toward maximizing the catalytic performance by advanced ion irradiation strategy.     

Dark plasmon of the rotated silver triangular nanoplate dimer

Rotated dimers are the common products during the deposition of Ag triangular nanoplates dimers on the glass substrate. In this work, modeling a silver dimer that it rotated around the Z axis shows that the wavelength and intensity of the dark plasmon are flexibly modulated by changing the angle’s rotation. Our results show that there are four main plasmonic bands. These resonances are formed due to the plasmon coupling between the dipole mode and quadrupole mode. In addition, the charge density distributions show a high degree of localization near both sides and corners of the nanotriangles. Moreover, It is found that the figure of merit (FOM) has the highest value for θ?=?71° due to the lowest value of the full wide at half maximum (FWHM) of the resonance peak. This study may be used to build optical sensors based on metallic nanoparticles with new plasmonic properties.     

Trimetallic Synergy in Intermetallic PtSnBi Nanoplates Boosts Formic Acid Oxidation

Platinum is the most effective metal for a wide range of catalysis reactions, but it fails in the formic acid electrooxidation test and suffers from severe carbon monoxide poisoning. Developing highly active and stable catalysts that are capable of oxidizing HCOOH directly into CO₂ remains challenging for commercialization of direct liquid fuel cells. A new class of PtSnBi intermetallic nanoplates is synthesized to boost formic acid oxidation, which greatly outperforms binary PtSn and PtBi intermetallic, benefiting from the synergism of chosen three metals. In particular, the best catalyst, atomically ordered Pt₄₅Sn₂₅Bi₃₀ nanoplates, exhibits an ultrahigh mass activity of 4394 mA mg^?1 Pt and preserves 78% of the initial activity after 4000 potential cycles, which make it a state‐of‐the‐art catalyst toward formic acid oxidation. Density functional theory calculations reveal that the electronic and geometric effects in PtSnBi intermetallic nanoplates help suppress CO* formation and optimize dehydrogenation steps.     

Dissolution-regrowth synthesis of SiO2 nanoplates and embedment into two carbon shells for enhanced lithium-ion storage

In this work, SiO_2 nanoplates with opened macroporous structure on carbon layer(C-mSiO_2) have been obtained by dissolving and subsequent regrowing the outer solid SiO_2 layer of the aerosol-based C-SiO_2 double-shell hollow spheres. Subsequently, triple-shell C-mSiO_2-C hollow spheres were successfully prepared after coating the Cm SiO_2 templates by the carbon layer from the carbonization of sucrose. When being applied as the anode material for lithium-ion batteries, the C-mSiO_2-C triple-shell hollow spheres deliver a high capacity of 501 mA ·h·g~(-1) after100 cycles at 500 m A·g~(-1)(based on the total mass of silica and the two carbon shells), which is higher than those of C-mSiO-12(391 m A·h·g~(-1)) spheres with an outer porous SiO_2 layer, C-SiO_2-C(370 m A·h·g) hollow spheres with a middle solid SiO_2 layer, and C-SiO_2(319.8 m A·h·g~(-1)) spheres with an outer solid SiO_2 layer. In addition,the battery still delivers a high capacity of 403 m A·h·g~(-1) at a current density of 1000 m A·g~(-1) after 400 cycles.The good electrochemical performance can be attributed to the high surface area(246.7 m~2·g~(-1)) and pore volume(0.441 cm~3·g~(-1)) of the anode materials, as well as the unique structure of the outer and inner carbon layer which not only enhances electrical conductivity, structural stability, but buffers volume change of the intermediate SiO_2 layer during repeated charge–discharge processes. Furthermore, the SiO_2 nanoplates with opened macroporous structure facilitate the electrolyte transport and electrochemical reaction.     

S‐Doped TiSe2 Nanoplates/Fe3O4 Nanoparticles Heterostructure

2D Sulfur‐doped TiSe₂/Fe₃O₄ (named as S‐TiSe₂/Fe₃O₄) heterostructures are synthesized successfully based on a facile oil phase process. The Fe₃O₄ nanoparticles, with an average size of 8 nm, grow uniformly on the surface of S‐doped TiSe₂ (named as S‐TiSe₂) nanoplates (300 nm in diameter and 15 nm in thickness). These heterostructures combine the advantages of both S‐TiSe₂ with good electrical conductivity and Fe₃O₄ with high theoretical Li storage capacity. As demonstrated potential applications for energy storage, the S‐TiSe₂/Fe₃O₄ heterostructures possess high reversible capacities (707.4 mAh g⁻¹ at 0.1 A g⁻¹ during the 100th cycle), excellent cycling stability (432.3 mAh g⁻¹ after 200 cycles at 5 A g⁻¹), and good rate capability (e.g., 301.7 mAh g⁻¹ at 20 A g⁻¹) in lithium‐ion batteries. As for sodium‐ion batteries, the S‐TiSe₂/Fe₃O₄ heterostructures also maintain reversible capacities of 402.3 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles, and a high rate capacity of 203.3 mAh g⁻¹ at 4 A g⁻¹.     

水热合成法制备Fe3O4纳米片及表征

用一种简单的水热法合成了平均粒径为400nm、厚度为70nm的Fe3O4纳米片,通过XRD、SEM对样品的结构、形貌进行了表征,用超导量子干涉仪（SQUID）对其磁学性能进行了研究,实验结果表明,反应温度、时间、搅拌速度均对产物的形貌产生重要影响。在常温下的磁学性能测量显示,其饱和磁化强度和矫顽力分别为94．60emu·g^-1,101 Oe,磁性能得到了较大改善。