ABSTRACT
The traditional Haber-Bosch process in industry to produce NH3 leads to excessive CO2 emissions and a large amount of energy consumption. Ambient electrochemical N2 reduction is emerging as a green and sustainable alternative method to convert N2 to NH3, but is in sore need of efficient and stable electrocatalysts. Herein, we propose using Pd-doped TiO2 nanoparticles as a high-efficiency electrocatalyst to synthesize NH3 under ambient conditions. The Pd-TiO2 catalyst delivers a large NH3 yield (17.4 µg h-1 mgcat.-1) and a high faradaic efficiency (12.7%) at -0.50 V versus reversible hydrogen electrode in a neutral electrolyte, outperforming most Pd- and Ti-based electrocatalysts recently reported for N2 reduction. Most importantly, it also demonstrates extraordinary long-term electrochemical stability.
ABSTRACT
Self-supported materials have been widely used in high-power energy storage devices due to the unique construction offering fast charge transfer from the active material to the conducting substrate. However, the electron conduction in the active material presents limitations on the overall performance of the electrode. In this work, we have fabricated hierarchical ZnO nanoflake arrays vertically grown on a nickel foam substrate and wrapped tightly by wrinkled porous CoS nanofilms (ZnO NFAs/CoS NFs) via a hydrothermal process and subsequent electrodeposition. Such an optimized ZnO NFAs/CoS NFs electrode exhibits an excellent specific capacitance of 1416 F g-1 at a current density of 1 A g-1, and remarkable cycling stability with 85.3% retention of the initial capacitance at 10 A g-1 after 5000 cycles. Additionally, density functional theory (DFT) calculations have been performed to further investigate the mechanism, proving the facilitated electron transfer from CoS to ZnO, giving rise to the superior electrochemical performance.
ABSTRACT
In this work, a free-standing flexible composite electrode was prepared by vacuum filtration method with LiFePO4, graphene and nanofibrillated cellulose (NFC). Compared with the pure LiFePO4 electrode, the resulting flexible composite (LiFePO4/graphene/NFC) electrode showed excellent mechanical flexibility, and possessed an enhanced initial discharge capacity of 151â¯mAâ¯h/g (0.1 C) and a good capacity retention rate with only 5% loss after 60â¯cycles due to suitable electrolyte wettability at the interface. Furthermore, the NFC and graphene formed a three-dimensional conductive framework, which provided high-speed electron conduction in the composite and reduced electrode polarization during charging-discharging processes. Moreover, the composite electrode could endure bending tests up to 1000 times, highlighting preferable mechanical strength and durability. These results demonstrated that the as-fabricated electrodes could be applied as flexible electrodes with an embedded power supply.
ABSTRACT
Conductive polymer composites (CPCs) containing nanoscale conductive fillers have been widely studied for their potential use in various applications. In this paper, polypyrrole (PPy)/polydopamine (PDA)/silver nanowire (AgNW) composites with high electromagnetic interference (EMI) shielding performance, good adhesion ability and light weight are successfully fabricated via a simple in situ polymerization method followed by a mixture process. Benefiting from the intrinsic adhesion properties of PDA, the adhesion ability and mechanical properties of the PPy/PDA/AgNW composites are significantly improved. The incorporation of AgNWs endows the functionalized PPy with tunable electrical conductivity and enhanced EMI shielding effectiveness (SE). By adjusting the AgNW loading degree in the PPy/PDA/AgNW composites from 0 to 50 wt%, the electrical conductivity of the composites greatly increases from 0.01 to 1206.72 S cm-1, and the EMI SE of the composites changes from 6.5 to 48.4 dB accordingly (8.0-12.0 GHz, X-band). Moreover, due to the extremely low density of PPy, the PPy/PDA/AgNW (20 wt%) composites show a superior light weight of 0.28 g cm-3. In general, it can be concluded that the PPy/PDA/AgNW composites with tunable electrical conductivity, good adhesion properties and light weight can be used as excellent EMI shielding materials.
ABSTRACT
Printed flexible electronics have been widely studied for their potential use in various applications. In this paper, a simple, low-cost method of fabricating flexible electronic circuits with high conductivity of 4.0 × 107 S·m-1 (about 70% of the conductivity of bulk copper) is demonstrated. Teslin paper substrate is treated with stannous chloride (SnCl2) colloidal solution to reduce the high ink absorption rate, and then the catalyst ink is inkjet-printed on its surface, followed by electroless deposition of copper at low temperature. In spite of the decrease in conductance to some extent, electronic circuits fabricated by this method can maintain function even under various folding angles or after repeated folding. This developed technology has great potential in a variety of applications, such as three-dimensional devices and disposable RFID tags.
ABSTRACT
Nanoscale LiFe0.92PO4 and LiFe0.92PO4/C/graphene composites including defects as performance-improved cathode materials for lithium-ion batteries were prepared by a carbothermal reduction method. The physical and electrochemical properties of samples were characterized by means of X-ray diffraction, inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and electrochemical testing techniques. The results confirmed that defects existed within the nanoscale LiFe0.92PO4 lattice and had significant effects on improving the electrochemical properties of samples. The excellent graphene sheets covered on nanoparticles and formed a three-dimensional conductive network in nanoscale LiFe0.92PO4/C/graphene composites. The composites exhibited a discharge capacity of 90 mA h g(-1) at 10 C and capacity retention ratios of 98% after 100 cycles at various rates, implying outstanding high-rate capability and cycling stability.
