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A MnO2 -CNT-graphene oxide (MCGO) nanocomposite is fabricated using graphene oxide (GO) as a surfactant to directly disperse pristine carbon nanotubes (CNTs) for the subsequent deposition of MnO2 nanorods. The resulting MCGO nanocomposite is used as a supercapacitor electrode that shows ideal capacitive behavior (i.e., rectangular-shaped cyclic voltammograms), large specific capacitance (4.7 times higher than that of free MnO2 ) even at high mass loading (3.0 mg cm(-2) ), high energy density (30.4-14.2 Wh kg(-1) ), large power density (2.6-50.5 kW kg(-1) ), and still retains approximately 94 % of the initial specific capacitance after 1000 cycles. The advanced capacity, rate capability, and cycling stability may be attributed to the unique architecture, excellent ion wettability of GO with enriched oxygen-containing functional groups, high conductivity of CNTs, and their synergistic effects when combined with the other components. The results suggest that the MnO2 -CNT-GO hybrid nanocomposite architecture is very promising for next generation high-performance energy storage devices.

A challenge in electrochemical CO 2 reduction is inhibiting hydrogen evolution reaction (HER). Herein, a bulk Zn electrode was chosen to reveal the effect of specifically adsorbed Cl − ions on HER during CO 2 reduction. We found that in the Cl − ion-containing electrolyte, the Zn−Cl adlayer formed because the weakly solvated Cl − ions can strip the solvation shell and form a direct chemical bond with the metal Zn. As a result, the Zn−Cl bonds on the Zn electrode notably blocked the hydrogen evolution and significantly facilitated the electron transfer process via the Cl to the vacant orbitals of inert CO 2 , therefore stabilizing the CO 2 − radical and leading to a four times higher CO Faradaic efficiency for CO 2 reduction in the KCl electrolyte than that in the KHCO 3 electrolyte at a moderate potential of −1.2 V versus a reversible hydrogen electrode.

This paper describes the effect of the frequency on energy harvesting in Pb(Zn1/3Nb2/3)0.955Ti0.045O3 single crystals with an Ericsson cycle. At the lowest frequency of 0.01 Hz (which corresponds to the slope for the application of the electric field), the maximum harvested energy was equal to 86 mJ cm−3. With an increase in frequency, the harvested energy demonstrated a nonlinear decrease, and the diminution was particularly rapid at frequencies above the critical frequency of 1 Hz. The inherent mechanism of the frequency effect is discussed in detail. In the present case, the phase transitions due to domain engineering, e.g., R-O during the charge process at low temperature and O-T during the discharging process at high temperature, greatly improved the harvested energy. The study also revealed that various parameters, such as the electric field associated with the phase transition, the polarization relaxation, and polarization variations, influenced the capability of energy harvesting to a certain extent. This capability depended significantly on the electric field frequency. Especially at high frequency, the reduction in the polarization time resulted in an inadequate phase transition, and subsequently gave rise to the coexistence of orthorhombic and rhombohedral phases. This had an adverse effect on the energy harvesting, and consequently, the harvested energy exhibited a decreasing tendency with an increasing electric field. Based on the result of the frequency effect, two asymmetric Ericsson cycles were attempted: an L-H cycle and an H-L cycle. These cycles employed different imposed frequencies at the charge and the discharge of the sample. Both asymmetric cycles agreed well with the performed analysis on the influence of the frequency. The H-L cycle greatly promoted energy harvesting, and its harvested energy reached 106 mJ cm−3, thus corresponding to the most effective energy harvesting cycle for this material.

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In this study, a series of ethylene glycol modified urea–melamine–formaldehyde resins were synthesized, and then incorporated into rigid polyurethane foams as a reactive-type liquid flame retardant.