Iron and nitrogen co-doped carbon (Fe-N/C) materials were fabricated by one-step pyrolysis of the mixture of FeCl3 and the low-cost biomass soybeans in N2 atmosphere at different temperatures. The ...physical properties of the prepared Fe-N/C catalysts were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) et al., the catalytic activity and stability of the Fe-N/C catalysts toward the oxygen reduction reaction (ORR) in alkaline solution were investigated by the electrochemical techniques. The results show that Fe is mainly in the form of Fe3O4 with the particle size of about 10nm and encapsulated by thin graphite layers, and the content of Fe decreases from 1.19 to 0.24wt.% with the increase of pyrolysis temperature from 600 to 900°C. The ORR activity on the sample prepared at 700°C (Fe-N/C-700) is preferable among the series of Fe-N/C catalysts, with the half-wave potential of the ORR shifting negatively only about 0.020V as compared to that on the commercial Pt/C (40wt.%, JM). The superior electro-catalytic performance of the Fe-N/C-700 catalyst would be due to the higher degree of the graphitization, the higher total contents of the pyridinic-N, quaternary-N/graphitic-N, as well as the relatively higher Fe3O4 content and surface area. The electron transfer number of the ORR on the Fe-N/C-700 catalyst approaches four indicating the 4-electron transfer pathway. Besides, the methanol tolerance and durability are superior to those on the Pt/C.
This paper introduces a new design route to fabricate nickel aluminum-layered double hydroxide (NiAl-LDH) nanosheets/hollow carbon nanofibers (CNFs) composite through an in situ growth method. The ...NiAl-LDH thin layers which grow on hollow carbon nanofibers have an average thickness of 13.6 nm. The galvanostatic charge–discharge test of the NiAl-LDH/CNFs composite yields an impressive specific capacitance of 1613 F g−1 at 1 A g−1 in 6 M KOH solution, the composite shows a remarkable specific capacitance of 1110 F g−1 even at a high current density of 10 A g−1. Furthermore, the composite remains a specific capacitance of 1406 F g−1 after 1000 cycles at 2 A g−1, indicating the composite has excellent high-current capacitive behavior and good cycle stability in compared to pristine NiAl-LDH.
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•Nickel aluminum-LDH grown on hollow carbon nanofibers by an in situ growth method.•NiAl-LDH/CNFs composite presents as three-dimensional network structure.•The composite exhibited a high specific capacitance of 1613 F g−1 at 1 A g−1.•Remarkable cycle performance at a current density of 2 A g−1.
We report a Ni-Al layered double hydroxide (LDH)-graphene superlattice composite via alternating assembly of the exfoliated thin flakes with opposite charges that show stable high-rate performance ...for alkaline battery cathodes.
Highly ordered TiO2 nanotube arrays (NTAs) with excellent stability and large specific surface area make them competitive using as supercapacitor materials. Improving the conductivity of TiO2 is of ...great concern for the construction of high-performance supercapacitors. In this work, we developed a novel approach to improve the performance of TiO2 materials, involving the fabrication of Al-doped TiO2 NTAs by a simple electrochemical cathodic polarization treatment in AlCl3 aqueous solution. The prepared Al-doped TiO2 NTAs exhibited excellent electrochemical performances, attributing to the remarkably improved electrical conductivity (i.e., from approx. 10 kΩ to 20 Ω). Further analysis showed that Al3+ ions rather than H+ protons doped into TiO2 lattice cause this high conductivity. A MnO2/Al–TiO2 composite was evaluated by cyclic voltammetry, and achieved the specific capacitance of 544 F g−1, and the Ragone plot of the sample showed a high power density but less reduction of energy density. These results indicate that the MnO2/Al–TiO2 NTAs sample could be served as a promising electrode material for high -performance supercapacitors.
•we report a mild electrochemical method to form Al-doped TiO2 nanotube arrays (NTAs).•Al-doped TiO2 NTAs show a highest electrical conductivity of approx. 20 Ω.•The elemental composition of Al-doped TiO2 NTAs were studied by XPS analysis.•Al-doped TiO2 were proved to be excellent supports materials for supercapacitors.
Reduced graphene oxide (rGO)-modified copper foil composite material was prepared by electrocoagulation of graphene oxide (GO) and a subsequent chemical reduction process. The effects of deposition ...voltages and the reduction time on the morphology, structure and electrochemical performances of the sample are investigated. The uniform surface morphology of GO/Cu sample obtained at a deposition voltage of 2.5 V. However, the appropriate chemical reduction not only improves the electrical conductivity of GO/Cu, but also enhances anticorrosion performance. At the optimized deposition voltages (2.5 V) and reduction time (20 min), the rGO/Cu shows the highest anticorrosive property and good conductivity. The protective efficiency of rGO/Cu is up to 98% (vs bare copper) as compared with 60% of GO/Cu according to Tafel analyses. The conductivity of rGO/Cu is close to bare copper according to the electrochemical impedance spectroscopy (EIS) results of Ni(OH)
2
/rGO/Cu and measurement of surface resistivity. We consider that rGO/Cu is a suitable material for realizing the copper foil manufacture with high corrosion resistance without sacrificing conductivity.
The influence of the dopant Bentonite, on the ionic conductivity of the PVA-KOH-H2O alkaline solid polymer electrolyte (ASPE) is studied. The results show that the addition of Bentonite has both ...positive and negative effects on the ionic conductivity of ASPE. At lower KOH and H2O contents, the addition of Bentonite can break the continuous ion conducting phase of the ASPE, and therefore decrease the ASPE conductivity. However, the addition of Bentonite can also increase the KOH content in PVA matrix. This greatly increases the conductivity of the ASPE especially at higher water content. A highest ionic conductivity of 0.11Scm-1 is reached at room temperature. A maximum ionic conductivity value is observed at relative lower water content for different amount of Bentonite-doped ASPE. The temperature dependence of the ionic conductivity is of the Arrhenius type. The ion transfer activation energy Ea, in the order of 4-6kJmol-1, heavily depends on the Bentonite content. XRD and SEM tests show that PVA in the Bentonite-doped ASPE is of amorphous structure, and there are lots of interspaces in the composite ASPE inner structure. The composite electrolyte has good electrochemical stability window and good charged-discharge property in secondary Zn-Ni cells at low charge-discharge rate.
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•A PEO adhesion strategy is proposed to solve the solid electrolyte/electrode interface issues.•The resistance of the modified solid/solid interface is decreased by two orders of ...magnitude.•The solid-state Li/LATP/LFP cell with sticky PEO interlayers exhibits steady cycling performance.
As a low-cost fast lithium ionic conductor with high shear modulus and ionic conductivity, Li1.3Al0.3Ti1.7(PO4)3 (LATP) is supposed to be one of the most promising ceramic electrolytes for high-energy solid-state batteries. However, the chemical reaction with lithium metal and the high interfacial impedance with solid electrodes make the ceramic electrolyte difficult to straightly apply to lithium metal batteries. Herein, a facile interfacial adhesion strategy is proposed to solve the addressed issues. The sticky polyethylene oxide (PEO) thin layer is served as interfacial adhesive to link the compact LATP ceramic electrolyte and the solid electrodes in consideration of its acceptable Li+ conducting capability and perfect compatibility with the tailored materials. Meantime, the PEO adhesive instead of PVDF binder is employed to glue the cathode components, enhancing the affinity to the PEO interlayer. As a result, the solid/solid interfacial resistance is decreased by two orders of magnitude. The solid-state Li/LATP/LiFePO4(LFP) cell with PEO adhesion is successfully activated, and exhibits steady cycling performance with high reversible capacity at the current no more than 0.5 C. As proposed interfacial adhesion strategy is simple but efficient to enable solid-state lithium metal batteries.
By Gouy–Chapman–Stern–Grahame (CGSG) model, the electric double layer at ion exchange membrane/solution interface consists of two parts: the Stern layer and the diffusion layer. The ions in Stern ...layer are compacted and considered to be immobile. The relation of diffusion layer mean conductivity
K with outer Stern layer potential
φ
0, the boundary potential
φ
δ
and the electrolyte concentration
C
0 is educed for symmetric electrolyte system. The results show that
K is higher than that of the bulk solution and is greatly influenced by
φ
0,
φ
δ
and
C
0.
The examination of PE01 cation exchange membrane/solution interface resistance
R
e measured by ac impedance technique, shows that
R
e value decreases quickly as the KCl electrolyte concentration rises. The effect of electrolyte concentration on the resistance of EDL can be explained by the electrical interactions between ions and charged groups of the membrane. Since the membrane/solution interface resistance is much higher than that of bulk solution, therefore, a further analysis based on the theory developed in this study proves that the ion transfer resistance
R
e of membrane–solution interface predominantly occurs at Stern layer as a result of static electrical interaction.
Hydroxyapatite (HA) was selected as dopant and synthesized by a sonochemical method in this study. PVA-HA-KOH-H2O composite alkaline solid polymer electrolyte (ASPE) was prepared by solution casting ...method. Two different doping routes, i.e., the physical mixing (PM) and in situ synthesis (ISS) were considered. The influences of the ASPE composition such as HA content, KOH content and water content on the conductivity were investigated. The ASPE prepared by ISS route has a porous structure which is important for ion transfer. Accordingly, the conductivity of the ASPE prepared by ISS is higher than that of by PM. A highest conductivity of about 0.1 S/cm is reached for ASPE prepared by ISS route at 70% water content for m(PVA):m(KOH):m(HA) = 10:14:10 system, higher than that of by PM route, 0.08 S/cm. The nickel/zinc cell shows better electrochemical properties assembled with the ASPE prepared by ISS approach than by PM approach.
