Preparation of Expanded Graphite and Graphite Nanosheets for Improving Electrical Conductivity of Polyester Coating Films

Expanded graphite and graphite nanosheets were facilely prepared by the thermal expansion of expandable graphite at 800 °C and sand milling of expanded graphite in water, respectively. When the expandable graphite precursor was prepared by the oxidation and intercalation of natural graphite (5 g) using KMnO4 (6 g) as an oxidant in a concentrated sulfuric acid solution (120 mL) at room temperature (25 °C) for 8 h, the expanded graphite with a maximum volumetric rate of 317 mL g−1 was prepared after the thermal expansion of the expandable graphite precursor at 800 °C for 60 s. The oxidation extent of natural graphite with KMnO4 is crucial for the preparation of expanded graphite. The thicknesses of graphite nanosheets decreased from 8.9 to 3.2 nm when the sand milling time of the expanded graphite in deionized water was prolonged from 6 to 24 h. The prolonging of the sand milling time not only decreased the layer number of the graphite nanosheet but also increased the d002 spacing due to the shocking and shearing forces. The addition of the expanded graphite powder and graphite nanosheets in a polyester paint efficiently improved the electrical conductivity of the resultant polyester coating films.

The Synergetic Effect of MoSO2/Graphite Nanosheets as Highly Efficient for Electrochemical Water Splitting in Acidic Media

Metal oxide nanoarchitectures have a wide range of qualities that can be used to produce novel technologies in the field of renewable energy, such as energy conversion solar fuels and storage via the photovoltaic effect, and electrochemical water splitting. The approach for the synthesis of earth abundant metal oxide nanostructures is facile and cost effective and involves scalable methodologies for the development of functional devices. The composite material exhibits enhanced active edge sites for the potential HER. The electrochemical experiments revealed satisfactory results of electrocatalytic gas production HER. The composite sample produces a current density at 10 mAcm−2 an over potential of 345 mV and Tafel value of 60 mVdec−1 it exhibits at which predominantly ensures the swift charge transfer kinetics during HER. The sample 3 remains durable and stable for 30 hours. EIS shown value of 21.88 Ohms as charge transfer resistance which further strengthened HER and Tafel results. The sample 3 exhibits a 4.69 µFcm−2 capacitance double layer and surface area of 177.25 cm2 it further supports the unique productivity for HER activity. The small Tafel slope which relatively close to Pt shows a clear and high potential of as prepared MoS2/Graphite nanosheets composite material for the replacement of noble metals in the field of renewable energy. The tiny Tafel slope value suggests that the efficient hydrogen evolution reaction has a lot of promise. This developed method provides the alternative method for the development of other materials for the energy harvesting applications.

Hierarchical Porous Graphene Bubbles as Host Materials for Advanced Lithium Sulfur Battery Cathode

The serious shuttle effect, low conductivity, and large volume expansion have been regarded as persistent obstacles for lithium sulfur (Li-S) batteries in its practical application. Carbon materials, such as graphene, are considered as promising cathode hosts to alleviate those critical defects and be possibly coupled with other reinforcement methods to further improve the battery performance. However, the open structure of graphene and the weak interaction with sulfur species restrict its further development for hosting sulfur. Herein, a rational geometrical design of hierarchical porous graphene-like bubbles (PGBs) as a cathode host of the Li-S system was prepared by employing magnesium oxide (MgO) nanoparticles as templates for carbonization, potassium hydroxide (KOH) as activation agent, and car tal pitch as a carbon source. The synthesized PGBs owns a very thin carbon layer around 5 nm that can be comparable to graphite nanosheets. Its high content of mesoporous and interconnected curved structure can effectively entrap sulfur species and impose restrictions on their diffusion and shuttle effect, leading to a much stable electrochemical performance. The reversible capacity of PGBs@S 0.3 C still can be maintained at 831 mAh g−1 after 100 cycles and 512 mAh g−1 after 500 cycles.