Two-Dimensional Double Hydroxide Nanoarchitecture with High Areal and Volumetric Capacitance

The development of high volumetric or areal capacitance energy storage devices is critical for the future electronic devices. Hence, the hunting for next-generation electrode materials and their design is of current interest. The recent work in the two-dimensional metal hydroxide nanomaterials demonstrates its ability as a promising candidate for supercapacitor due to its unique structure and additional redox sites. This study reports a design of freestanding high-mass-loaded copper-cobalt hydroxide interconnected nanosheets for high-volumetric/areal-performance electrode. The unique combination of hydroxide electrode with high mass loading (26 mg/cm(2)) exhibits high areal and volumetric capacitance of 20.86 F/cm(2) (1032 F/cm(3)) at a current density of 10 mA/cm(2). This attributes to the direct growth of hydroxides on porous foam and conductivity of copper, which benefits the electron transport. The asymmetric supercapacitor device exhibits a high energy density of 21.9 mWh/cm(3), with superior capacitance retention of 96.55% over 3500 cycles

Synergistic effects of graphene oxide grafted chitosan & decorated MnO2 nanorods composite materials application in efficient removal of toxic industrial dyes

Abstract In this study, we designed a heterogeneous graphene oxide (GO) grafted on chitosan decorated with MnO2 nanorods (α-MnO2NRs/GO-Chit) composite materials and its ability to remove the cationic and anionic toxic dyes from wastewaters were analysed. The synthesised materials presented an effective stabilization of active MnO2 nanorods (NRs) on the GO-Chit surface. The synthesised materials were detailed characterised by several spectroscopic and microscopic techniques such as, FT-IR, P-XRD, SEM, TEM, Raman, TGA, XPS, BET, CO2-TPD and UV–Visible analysis. In addition, α-MnO2NRs/GO-Chit material is successfully applied in removal of industrial ionic dyes such as amido black 10B (AB) and methylene blue (MB), respectively. The dye adsorption experiments confirmed that the GO-Chit/α-MnO2 NRs material exhibited remarkably high adsorption capacity in efficient removal of cationic dye methylene blue (MB) and anionic dye amido black 10B (AB). The maximum MB dye removal (97%) process completed in 24 min at C0 = 30 mg·L-1, but in the case of AB the maximum dye removal (80%) process was reached in 700 min. Over GO-Chit/α-MnO2 NRs hybrid material, a maximum theoretical monolayer adsorption (qmax values is 328.9 mg g-1) of MB was calculated from the Langmuir isotherm equation. In case MB, a faster adsorption and 2.18 times maximum adsorption capacity was achieved than that of AB10 dye. The enhanced adsorption over α-MnO2NRs/GO-Chit is due to the increased surface functionalities (i.e., oxygen-containing groups), high basicity and strong electrostatic forces between MnO2 nanorods and GO-Chit. Furthermore, α-MnO2NRs/GO-Chit hybrid material displayed good stability after 10 successive adsorption tests

Morphologically tailored facet dependent silver nanoparticles supported α-Al₂O₃ catalysts for chemoselective reduction of aromatic nitro compounds

Abstract The nanoparticles surface area, intrinsic sites, exposed microcrystal shapes and lattice planes are some of the key factors in nanocatalysis. The influence of nanoparticles shape dependent had been profound effect on its catalytic activity. This study is focused on the synthesis of morphologically shape-controlled silver (Ag) nanoparticles supported on α-Al₂O₃ catalysts were performed. The correlation of Ag NPs with varied facets and lattice planes on the catalytic activities in chemoselective reduction of nitro compounds was investigated. Engineering the silver nanoparticles with different shapes and facets i.e., nanocubes (AgNCs), nanowires (AgNWs) and nano spheres (AgNSPs) were synthesized by using modified polyol method. It is demonstrated that there is a significant difference in their activities with respect to the shape and nanocrystal facets. The evolution of nanoshapes and the structural properties of Ag nanoparticles were analysed by SEM, TEM, HR-TEM and P-XRD techniques. From XRD, Ag nanocubes exhibited high percentage of low index (1 0 0) facets which are favourable active centers than (1 1 1) plane in nitro reduction. We observed that the silver nanocubes selectively exposed (1 0 0) facets, which are highly favorable for the enhanced catalytic activity in nitro reduction. The reaction rate of nitro phenol to amino phenol over different Ag nanoshapes are 35.01×10−3min−1(AgNCs/Al₂O₃), 8.28×10−3min−1(AgNWs/Al₂O₃), 0.65×10−3 min−1(AgNSPs/Al₂O₃), respectively. The calculated thermodynamic parameters of the Ea values 23.6, 28.6 and 29.4 for the AgNC, AgNWs and AgNSP respectively