Recently, aqueous
Zn-ion rechargeable batteries have drawn increasing
research attention as an alternative energy storage system relative
to the current Li-ion batteries due to their intrinsic properties
of high safety, low cost, and high theoretical volumetric capacity.
Nevertheless, unwanted dendrite growth on the Zn anode and unstable
cathode materials restrict their practical application. In this study,
a unique 2D MoS2 coating on a Zn anode using an electrochemical
deposition method has been developed for preventing dendrite growth
and intricate side reactions. The coated MoS2 layer is
a vertically oriented structure that makes the flow of Zn ions easy
with a uniform electric field distribution on the anode, resulting
in a uniform stripping and plating of Zn2+. In addition,
the MoS2 coating enhances anodic diffusion of Zn ions and
reduces the series resistance as confirmed by EIS analysis and therefore
improves the overall battery performance. The full cell assembled
with the MoS2–Zn anode and MnO2 cathode
exhibits an excellent reversible specific capacity of 638 mAh/g at
0.1 A/g and stable cycle performance over 2000 cycles with no dendrite
formation at the Zn electrode. The presented MoS2 coating
on Zn is a facile, scalable, and promising technology for practical
Zn-ion batteries with a long life cycle and high safety.
Polyurethane foams are in general flammable and their flammability can be controlled by adding flame-retardant (FR) materials. Reactive FR have the advantage of making strong bond within the polyurethane chains to provide excellent FR over time without compromising physico-mechanical properties. Here, phenyl phosphonic acid and propylene oxide-based reactive FR polyol was synthesized and used along with limonene based polyol for preparation of FR polyurethanes. All the obtained foams showed higher closed cell content (above 96%). By the addition of FR-polyol, the compressive strength of the foams showed 160% increment which could be due to reactive nature of FR-polyol. Moreover, 1.5 wt % of phosphorus (P) content reduced the self-extinguishing time of the foam from 81 (28% weight loss) to 11.2 s (weight loss of 9.8%). Cone test showed 68.6% reduction in peak heat release rate along with 23.4% reduction in thermal heat release. The change in char structure of carbon after burning was analyzed using Raman spectra which, suggests increment in the graphitic phase of the carbon over increased concentration of phosphorus. It can be concluded from this study that phosphorous based polyol could be blended with bio-based polyols to prepare highly FR and superior physico-mechanical rigid polyurethane foams.
Rapidly increasing markets for electric vehicles (EVs), energy storage for backup support systems and high-power portable electronics demand batteries with higher energy densities and longer cycle lives.
Abstract:Hydrogen is an efficient fuel which can be generated via water splitting, however hydrogen evolution occurs at high overpotential, and efficient hydrogen evolution catalysts are desired to replace state-of-the-art catalysts such as platinum. Here, we report an advanced electrocatalyst that has low overpotential, efficient charge transfers kinetics, low Tafel slope and durable. Carbon nanofibers (CNFs), obtained by carbonizing electrospun fibers, were decorated with MoS 2 using a facile hydrothermal method. The imaging of catalyst reveals a flower like morphology that allows for exposure of edge sulfur sites to maximize the HER process. HER activity of MoS 2 decorated over CNFs was compared with MoS 2 without CNFs and with commercial MoS 2 . MoS 2 grown over CNFs and MoS 2 -synthesized produced about 374 and 98 times higher current density at −0.30 V (vs. Reversible Hydrogen Electrode, RHE) compared with the MoS 2 -commercial sample, respectively. MoS 2 -commercial, MoS 2 -synthesized and MoS 2 grown over CNFs showed a Tafel slope of 165, 79 and 60 mV/decade, capacitance of 0.99, 5.87 and 15.66 mF/cm 2 , and turnover frequency of 0.013, 0.025 and 0.54 s −1 , respectively. The enhanced performance of MoS 2 -CNFs is due to large electroactive surface area, more exposure of edge sulfur to the electrolyte, and easy charge transfer from MoS 2 to the electrode through conducting CNFs.
The development of cost-effective, functional materials that can
be efficiently used for sustainable energy generation is highly desirable.
Herein, a new molecular precursor of bismuth (tris(selenobenzoato)bismuth(III),
[Bi(SeOCPh)
3
]), has been used to prepare selectively Bi
or Bi
2
Se
3
nanosheets via a colloidal route by
the judicious control of the reaction parameters. The Bi formation
mechanism was investigated, and it was observed that the trioctylphosphine
(TOP) plays a crucial role in the formation of Bi. Employing the vapor
deposition method resulted in the formation of exclusively Bi
2
Se
3
films at different temperatures. The synthesized
nanomaterials and films were characterized by p-XRD, TEM, Raman, SEM,
EDX, AFM, XPS, and UV–vis spectroscopy. A minimum sheet thickness
of 3.6 nm (i.e., a thickness of 8–9 layers) was observed for
bismuth, whereas a thickness of 4 nm (i.e., a thickness of 4 layers)
was observed for Bi
2
Se
3
nanosheets. XPS showed
surface oxidation of both materials and indicated an uncapped surface
of Bi, whereas Bi
2
Se
3
had a capping layer of
oleylamine, resulting in reduced surface oxidation. The potential
of Bi and Bi
2
Se
3
nanosheets was tested for overall
water-splitting application. The OER and HER catalytic performances
of Bi
2
Se
3
indicate overpotentials of 385 mV
at 10 mA cm
–2
and 220 mV, with Tafel slopes of 122
and 178 mV dec
–1
, respectively. In comparison, Bi
showed a much lower OER activity (506 mV at 10 mA cm
–2
) but a slightly better HER (214 mV at 10 mA cm
–2
) performance. Similarly, Bi
2
Se
3
nanosheets
were observed to exhibit cathodic photocurrent in photoelectrocatalytic
activity, which indicated their p-type behavior.
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