[en] Electromagnetic composites have wide application in the functional devices. For the best performance of devices, the regulation of the electrical impedance has been being desired for the impedance matching in service. However, the keeping of impedance matching in service is quite challenging. In the present work, a mechanical method for tuning the electrical impedance of La_0.7Sr_0.3MnO₃/0.72Pb(Mg_1/3Nb_2/3)O₃−0.28PbTiO₃ (LSMO/PMN-PT) based on the nanocontact technique is proposed. It is found that the electrical impedance reduces with the increase of the nanocontact load. A linear relationship is found between the square of impedance magnitude and the inverse of nanocontact depth. Furthermore, a method for predicting the contact-depth-dependent impedance magnitude of LSMO/PMN-PT is proposed. (paper)

[en] Single-crystalline tetrapod-like ZnS nanopods were synthesized by a one-step seed-epitaxial metal-organic chemical vapor deposition (MOCVD) approach using cubic CdSe nanocrystals as the seeds. The diameters of the ZnS tetrapods can be easily tuned by changing the distances between the substrates and precursors. A possible growth mechanism is discussed on the basis of the heterostructure epitaxial growth. The ZnS tetrapod has a zinc CdSe nanocrystal core at the center with four wurtzite ZnS arms growing out from the core along four [0001] directions. Due to the lower temperature and versatility, this controllable seed-epitaxial method has potential as a general means of forming complex branching structures and may also offer opportunities for applications as building blocks for optoelectronic devices. - Graphical abstract: Single-crystalline tetrapod-like ZnS nanopods were synthesized by a one-step seed-epitaxial metal-organic chemical vapor deposition approach using cubic CdSe nanocrystals as the seeds. The diameters of the ZnS tetrapods can be easily tuned by changing the distances between the substrates and precursors

[en] Highlights: • Hydrothermal-prepared RuO_2-SnO_2 was added to XC-72 carbon black as composite support. • (Ru,Sn)O_2 solid solution increases the EAS and specific activity of Pd. • (Ru,Sn)O_2 changes the electron structure of Pd 3d and reduces CO coverage on Pd. • (Ru,Sn)O_2 solid solution also enhances the OH_a_d_s adsorption on Pd surface. • Pd/RuO_2-SnO_2/C catalyst shows highest activity and stability for EG oxidation. - Abstract: In this paper, RuO_2-SnO_2 binary oxides were prepared using a hydrothermal approach and added to Vulcan XC-72 carbon black as new support material for Pd. The X-ray diffraction, Transmission electron microscopy and X-ray photoelectronic spectra results show that the addition of binary oxides leads to the formation of (Ru,Sn)O_2 solid solution in Pd/C catalyst and reduces the particle size of Pd particles due to the anchoring effect. In addition, the electrochemical CO-striping measurement reveals that the Pd/RuO_2-SnO_2/C catalyst exhibits the largest electrochemical active surface and the best CO tolerance. Moreover, cyclic voltammetry and chronoamperometry tests demonstrate that the Pd/RuO_2-SnO_2/C catalyst possesses a much higher specific activity (4.4 mA cm"−"2) than that of the Pd/C catalyst (3.2 mA cm"−"2) towards ethylene glycol electrooxidation in alkaline media, and better stability as well. These results support the suitability of Pd/RuO_2-SnO_2/C catalyst developed in this work as a promising candidate for direct alcohol fuel cells (DAFCs) application

[en] Graphical abstract: We rationally design and synthesize a ternary PdRuBi/NG catalyst with significantly enhanced catalytic activity with synergetic effect of Ru and Bi towards ethylene glycol electro-oxidation. - Abstract: Palladium (Pd)-based catalysts are appealing electro-catalysts for alcohol oxidation reaction in fuel cell, but still not efficient as the complicated oxidation process and sluggish kinetic. Here we rationally design and synthesize a PdRuBi/NG tri-metallic catalyst with space synergetic effect for enhanced ethylene glycol electro-oxidation, in which both Ru and Bi in the catalyst are synergistic effective in promoting catalytic activity of Pd catalytic interlayer by electronic effect and surface modification mechanism respectively. It shows 4.2 times higher peak current density towards ethylene glycol electro-oxidation than commercial Pd/C catalyst, and the catalytic durability is also greatly improved.

[en] Highlights: • Thermal-decomposed CaSiO_3 was added to XC-72 carbon black as composite support. • Modified electronic structure of Pd facilitates the detachment of CO from Pd surface. • CaSiO_3 enhances proton transfer process and improves dehydrogenation process. • CaSiO_3 promotes oxidation removal of CO due to easier OH− adsorption on electrode. • Pd/50CaSiO_3/C catalyst shows highest activity and stability for ethanol oxidation. - Abstract: In this paper, CaSiO_3 was prepared using a thermal decomposition approach and added to Vulcan XC-72 carbon black as support material. The X-ray diffraction and Transmission electron microscopy results show that the addition of CaSiO_3 does not significantly change the particle size and distribution of Pd nanoparticles. The X-ray photoelectron spectroscopy reveals the interaction between Pd and CaSiO_3. In addition, the electrochemical CO-striping measurement reveals that the Pd/50CaSiO_3/C catalyst exhibits the largest electrochemical active surface and best CO tolerance. Moreover, cyclic voltammetry and chronoamperometry tests demonstrate that the Pd supported by CaSiO_3 and C (50:50 in wt.%) possesses a much higher current density (1408 mA mg"−"1) than that of the Pd/C catalyst (743 mA mg"−"1) towards ethanol oxidation in alkaline media, and better stability as well. These results support the suitability of Pd/50CaSiO_3/C catalyst developed in this work as a promising candidate for direct ethanol fuel cells application

[en] Lithium–sulfur battery is one of the most promising energy storage systems for its high specific capacity. However, commercial development of lithium–sulfur batteries is severely hindered by the cathode host materials. To tackle this issue, we synthesized a new host material, high surface area, three-dimensional (3D) diamond-cage porous polymer frameworks PPN-13, to construct sulfur electrode by impregnating sulfur into its nano-pores. The PPN-13-S cathode deliveries a specific discharge capacity up to 606.4 mA h/g over 100 cycles at 0.1 C with a high coulombic efficiency. It demonstrates that the 3D porous structure PPN-13 as host material shows the high performance and a remarkable positive effect on the capacity retention as cathode materials in lithium–sulfur batteries. Due to the unique features of the material, our research provides a new type of materials for tailoring cathode materials in lithium–sulfur batteries. - Highlights: • A high surface area host material PPN-13 was used in lithium–sulfur battery. • The host material PPN-13 exist vast nano-porous 3D diamond-cage structure. • The host material can efficient suppress the diffusive of polysulfide. • The unique host material impregnated sulfur present excellent electrochemical performance.

[en] Highlights: • Li_1_._2Mn_0_._5_6Ni_0_._1_2Co_0_._1_2O_2 with different shapes was successfully prepared. • The solvent plays a key role in the formation of the product with various shapes. • The sample prepared by solvothermal method exhibits higher discharge capacity. • Its reversible capacity is approximately 306.9 mA h g"−"1 at 0.2 C. - Abstract: A Li-rich layered cathode material Li_1_._2Mn_0_._5_6Ni_0_._1_2Co_0_._1_2O_2 (0.5Li_2MnO_3⋅0.5Li_1_._2Mn_0_._4Ni_0_._3Co_0_._3O_2) with different morphologies has been successfully prepared by solvothermal and hydrothermal methods. The result demonstrates that the solvent plays a crucial role in the formation of the precursor and final product with various shapes and sizes. When tested as the cathode material for lithium ion batteries, the sample prepared by solvothermal method exhibits higher discharge capacity, better cycling performance, and more excellent rate capacity. It delivers a discharge capacity of 306.9 mA h g"−"1 at 0.2 C and 118.6 mA h g"−"1 even at a high rate of 5.0 C. The outstanding performance of the sample prepared by solvothermal method can be attributed to the well-ordered structure and well-defined morphology with smaller particle size and uniform distribution. The current study paves a new concept and applicable way to prepare high performance Li-rich layered cathode material for LIBs

[en] Highlights: • SnO_2@rGO–carbon particles framework nanoarchitecture was prepared by facile coprecipitation. • The SnO_2@rGO–carbon particles nanoarchitecture could tune the electrochemical properties. • SnO_2@rGO–BP2000 shows the best cycling performance. • The SnO_2@rGO–carbon particle guarantees effectively lithium ion/electron conductivity. - Abstract: A series of novel nanoarchitectures of SnO_2@rGO–carbon inserted with carbon nanoparticles of BP2000 and KJ600 was successfully prepared by a facile coprecipitation method. TGA, XRD, SEM, TEM and Raman spectrom analysis are carried out and indicate that SnO_2 nanoparticles and carbon intermediates are uniformly dispersed on graphene nanosheets at a molecular level, forming the framework nanoarchitectures of SnO_2@rGO–carbon particles. SnO_2@rGO–BP2000 delivers a discharge capacity of 1284.4 mAhg"−"1 and 76% retention of the reversible capacities after 60 cycles at an initial current density of 100 mAg"−"1. SnO_2@rGO–BP2000 also showed the best rate performance among three anode materials at both high and low rate. The outstanding performance of the SnO_2@rGO–BP2000 is attributed to well-defined morphology with suitable particle size, uniform distribution as well as enough room for the SnO_2 volume expansion based on the graphene–carbon particles framework

[en] Highlights: • Mechanistic understanding of key determinants that lead to surface evolution is offered. • Four forms of surface evolution are summarized with highlighting advanced characterization techniques. • Real active sites of typical electrocatalysts are revealed to uncover the structure-performance relationship. • Control strategies that accelerate favorable surface evolution and decelerate the adverse cases are summarized. • The findings are concluded for more rigorous identification of real active sites after surface evolution. To develop and improve electrocatalysts for promising energy conversion reactions, an in-depth understanding of their active sites is essential. In real operating conditions, the active sites could be subjected to various structural/chemical evolutions, as revealed recently by post-catalysis/in-situ characterizations. Insightful understanding suggests that multiple interactions between electric field, electrolyte, reactant/intermediate/resultant, and electrocatalyst increase the mutability of the electrocatalyst surfaces, triggering the surface evolution. Hence, the surface evolution causes the deviation of the initial design of active sites from the real ones. It calls for re-identification of active sites responsible for the observed activity and further provides more accurate guidelines for rational electrocatalytic design. This review reveals the origin of surface evolution, summarizes the general forms involving composition leaching, phase transformation, atom rearrangement, and metastable intermediate from typical electrocatalysts. It also proposes control strategies toward the formation or reservation of stable highly-active sites by atomic/defective modulation, interfacial coupling, structural optimization of pre-synthesis, and forming a protective layer. The active sites of typical electrocatalysts are identified and elucidated before and after the surface evolution. The current challenges in developing electrocatalysts addressing the definite structure-performance relationship, advanced characterization techniques, and strategies for more rigorous identification of real active sites after surface evolution are presented.

[en] Highlights: • A novel N-doped graphene supported PdPb nanocatalyst was prepared. • N-doped graphene facilitates more uniform dispersion of metal particles than graphene. • Current for ethanol oxidation of PdPb/NG (152.3 mA cm"−"2) is 4 times higher than Pd/G. • PdPb/NG catalyst shows excellent catalytic durability among the catalysts. • Catalytic performance was enhanced by the bifunctional mechanism and electronic effect. - Abstract: In this work, a series of palladium and palladium-lead nanoparticles supported on active carbon, graphene and nitrogen-doped graphene are synthesized via a one-step reduction method. Atomic absorption spectroscopy, X-ray powder diffraction, transmission electron microscope and X-ray photoelectron spectroscopy are used to characterize the catalysts. The results indicate that metal nanoparticles are more uniformly dispersed on the surface of N-doped graphene than those on graphene, without any aggregation. Various electrochemical techniques are carried out to evaluate the electrocatalytic ethanol oxidation activity and durability. The peak current for ethanol electrooxidation of Pd/N-doped graphene increases to 70.2 mA cm"−"2, obviously higher than that of Pd/Graphene (38.0 mA cm"−"2) and even surpasses that of Pd/C (51.9 mA cm"−"2). N-doped graphene support not only possesses faster dehydrogenation but provides an electron effect to Pd. Introduction of Pb into the catalyst causes the formation of abundant oxygenated species on the catalyst surface at low potential. Based on the synergistic effect of N and Pb towards Pd particles, the PdPb/N-doped graphene catalyst (Pd:Pb = 8:1.0) exhibits remarkably enhanced activity up to 152.3 mA cm"−"2 for ethanol oxidation, which is 4.0 and 2.9 times higher than that of Pd/Graphene and Pd/C, respectively. The catalytic durability and stability are also greatly improved