New synthesized ionic liquid functionalized graphene oxide: Synthesis, characterization and its nanocomposite with conjugated polymer as effective electrode materials in an energy storage device

Morphology-Tuned Pt3 Ge Accelerates Water Dissociation to Industrial-Standard Hydrogen Production over a wide pH Range

The discovery of novel materials for industrial-standard hydrogen production is the present need considering the global energy infrastructure. A novel electrocatalyst, Pt₃ Ge, which is engineered with a desired crystallographic facet (202), accelerates hydrogen production by water electrolysis, and records industrially desired operational stability compared to the commercial catalyst platinum is introduced. Pt₃ Ge-(202) exhibits low overpotential of 21.7 mV (24.6 mV for Pt/C) and 92 mV for 10 and 200 mA cm^-2 current density, respectively in 0.5 m H₂ SO₄ . It also exhibits remarkable stability of 15 000 accelerated degradation tests cycles (5000 for Pt/C) and exceptional durability of 500 h (@10 mA cm^-2 ) in acidic media. Pt₃ Ge-(202) also displays low overpotential of 96 mV for 10 mA cm^-2 current density in the alkaline medium, rationalizing its hydrogen production ability over a wide pH range required commercial operations. Long-term durability (>75 h in alkaline media) with the industrial level current density (>500 mA cm^-2 ) has been demonstrated by utilizing the electrochemical flow reactor. The driving force behind this stupendous performance of Pt₃ Ge-(202) has been envisaged by mapping the reaction mechanism, active sites, and charge-transfer kinetics via controlled electrochemical experiments, ex situ X-ray photoelectron spectroscopy, in situ infrared spectroscopy, and in situ X-ray absorption spectroscopy further corroborated by first principles calculations.

Performance of novel GO-Gly/HNTs and GO-GG/HNTs nanocomposites for removal of Pb(II) from water: optimization based on the RSM-CCD model

For the first time, in this study, two novel glycogen-graphene oxide/halloysite nanotubes (GO-Gly/HNTs) and guar gum-graphene oxide/halloysite nanotubes (GO-GG/HNTs) nanocomposites were synthesized as the adsorbents for removal of Pb(II) from water, and the ionic liquid was used in the synthesis as a green solvent. According to the SEM, TEM, EDS, BET, zeta potential, FTIR, and XRD results, GO-Gly/HNTs and GO-GG/HNTs were synthesized successfully. Response surface methodology (RSM) was applied to optimize the experimental conditions. Nanocomposites followed the Langmuir equilibrium model and were best fitted to the pseudo-second-order model. According to the thermodynamic model, the adsorption process was endothermic. Due to several features, these two novel nanocomposites can be considered the proper candidate for Pb(II) removal from water and wastewater. First, these nanocomposites have good adsorption capacity for Pb(II) removal, which is 219 mg/g for GO-Gly/HNTs and 315 mg/g for GO-GG/HNTs. Moreover, nanocomposites can be recycled with proper adsorption capacity after four repeated cycles. These materials can be used to remove Pb(II) from water in the presence of other contaminants because nanocomposites have selective tendency toward Pb(II) in the presence of other pollutants such as Cd²⁺, Cu²⁺, Cr²⁺, and Co²⁺. In addition, the presence of Ca²⁺, Mg²⁺, Na⁺, and K⁺ improve Pb(II) removal. Finally, possible mechanisms for each nanocomposite were represented.

Hydroxyl-assisted selective epoxidation of perillyl alcohol with hydrogen peroxide by vanadium-substituted phosphotungstic acid hinged on imidazolyl activated carbon

Vanadium-substituted phosphotungstic acid hinged on imidazolyl activated carbon catalyzed efficiently and stably the selective epoxidation of perillyl alcohol with H2O2.

Plant polyphenols induced the synthesis of rich oxygen vacancies Co3O4/Co@N-doped carbon hollow nanomaterials for electrochemical energy storage and conversion

Reasonable hollow structure design and oxygen vacancy defects control play an important role in the optimization of electrochemical energy storage and electrocatalytic properties. Herein, a plant polyphenol tannic acid was used to etch Co-based zeolitic imidazolate framework (ZIF-67) followed by calcination to prepare a porous Co₃O₄@Co/NC hollow nanoparticles (Co₃O₄@Co/NC-HN) with rich oxygen vacancy defects. Owing to the metal-phenolic networks (MPNs), rich oxygen vacancy defects and the synergistic effect between Co₃O₄ and Co/NC, the box-like Co₃O₄@Co/NC-HN nanomaterials with large specific surface areas exhibit excellent supercapacitor performance and electrocatalytic activity. As expected, Co₃O₄@Co/NC-HN shows high specific capacity (273.9 mAh g^-1 at 1 A g^-1) and remarkable rate performance. Moreover, the assembled Hybrid supercapacitor (HSC, Co₃O₄@Co/NC-HN//Active carbon) device obtained a maximum energy density of 57.8 Wh kg^-1 (800 W kg^-1) and exhibited superior cycle stability of 92.6% after 4000 cycles. Notably, as an electrocatalyst, the nanocomposites exhibit small overpotential and Tafel slope. These results strongly demonstrate that both unique hollow structure and abundant oxygen vacancies designed from plant polyphenols provide superiorities for the synthesis of efficient and green multifunctional electrode materials for energy storage and conversion.

When graphene meets ionic liquids: a good match for the design of functional materials

Graphene is an attractive material that is characterized by its exceptional properties (i.e. electrical, mechanical, thermal, optical, etc.), which have pushed researchers to attach high interest to its production and functionalization processes to meet applications in different fields (electronics, electromagnetics, composites, sensors, energy storage, etc.). The synthesis (bottom-up) of graphene remains long and laborious, at the same time expensive, and it is limited to the development of this material in low yield. Hence, the use of graphite as a starting material (top-down through exfoliation or oxidation) seems a promising and easy technique for producing a large quantity of graphene or graphene oxide (GO). On the one hand, GO has been extensively studied due to its ease of synthesis, processing and chemical post-functionalization. One the other hand, "pristine" graphene sheets, obtained through exfoliation, are limited in processability but present enhanced electronic properties. Both types of materials have been of great interest to design functional nanomaterials. Ionic liquids (ILs) are task-specific solvents that exhibit tunable physico-chemical properties. ILs have many advantages as compared with conventional solvents, such as high thermal and chemical stability, low volatility, excellent conductivity and inherent polarity. In the last decade, ILs have been widely employed for the preparation and stabilization of various nanomaterials. In particular, the combination of ILs and graphene, including GO and pristine graphene sheets, has been of growing interest for the preparation, processing and functionalization of hybrid nanomaterials. Understanding the structure and properties of the graphene/IL interface has been of considerable interest for a large panel of applications ranging from tribology to energy storage.

Efficient Photocatalytic Degradation of Gaseous Benzene and Toluene over Novel Hybrid PIL@TiO2/m-GO Composites

In this work, the PIL (poly ionic liquid)@TiO2 composite was designed with two polymerized ionic liquid concentrations (low and high) and evaluated for pollutant degradation activity for benzene and toluene. The results showed that PIL (low)@TiO2 composite was more active than PIL (high)@TiO2 composites. The photodegradation rate of benzene and toluene pollutants by PIL (low)@TiO2 and PIL (high)@TiO2 composites was obtained as 86% and 74%, and 59% and 46%, respectively, under optimized conditions. The bandgap of TiO2 was markedly lowered (3.2 eV to 2.2 eV) due to the formation of PIL (low)@TiO2 composite. Besides, graphene oxide (GO) was used to grow the nano-photocatalysts’ specific surface area. The as-synthesized PIL (low)@TiO2@GO composite showed higher efficiency for benzene and toluene degradation which corresponds to 91% and 83%, respectively. The resultant novel hybrid photocatalyst (PIL@TiO2/m-GO) was prepared and appropriately characterized for their microstructural, morphology, and catalytic properties. Among the studied photocatalysts, the PIL (low)@TiO2@m-GO composite exhibits the highest activity in the degradation of benzene (97%) and toluene (97%). The ultimate bandgap of the composite reached 2.1 eV. Our results showed that the as-prepared composites hold an essential role for future considerations over organic pollutants.

Synthesis of Holey Graphene Nanoparticle Compounds

Bulk-scale syntheses of sp² nanocarbon have typically been generated by extensive chemical oxidation to yield graphite oxide from graphite, followed by a reductive step. Materials generated via harsh random processes lose desirable physical characteristics. Loss of sp² conjugation inhibits long-range electronic transport and the potential for electronic band manipulation. Here, we present a nanopatterned holey graphene material electronically hybridized with metal-containing nanoparticles. Oxidative plasma etching of highly ordered pyrolytic graphite via previously developed covalent organic framework (COF)-5-templated patterning yields bulk-scale materials for electrocatalytic applications and fundamental investigations into band structure engineering of nanocomposites. We establish a broad ability (Ag, Au, Cu, and Ni) to grow metal-containing nanoparticles in patterned holes in a metal precursor-dependent manner without a reducing agent. Graphene nanoparticle compounds (GNCs) show metal-contingent changes in the valence band structure. Density functional theory investigations reveal preferences for uncharged metal states, metal contributions to the valence band, and embedding of nanoparticles over surface incorporation. Ni-GNCs show activity for oxygen evolution reaction in alkaline media (1 M KOH). Electrocatalytic activity exceeds 10,000 mA/mg of Ni, shows stability for 2 h of continuous operation, and is kinetically consistent via a Tafel slope with Ni(OH)₂-based catalysis.

Core-shell nanowires of NiCo2O4@α-Co(OH)2 on Ni foam with enhanced performances for supercapacitors

The composites of NiCo₂O₄ with unique structures are extensively explored as promising electrodes. In this work, core-shell structured nanowires anchored on nickel foam are synthesized by the hydrothermal synthesis of NiCo₂O₄ as core and subsequent electrodeposition of α-Co(OH)₂ as shell. The core-shell composites exhibit enhanced electrochemical performances ascribing to the synergistic reactions from both materials, showing higher specific capacitance than any single component. By changing the deposition time, the mass loading of α-Co(OH)₂ can be easily controlled. The electrochemical performances of the hybrid electrodes are diverse with the mass loading of Co(OH)₂. The optimized hybrid electrode with 3 mins electrodeposition exhibits the highest specific capacitance (1298 F g^-1 at 1 A g^-1) among all electrodes. The redox reaction is a main contributor to the total specific capacitance through electrochemical kinetics analysis. An asymmetric supercapacitor assembled by the optimized material as positive electrode and activated carbon as negative electrode can achieve a relatively high energy density of 39.7 Wh kg^-1 at a power density of 387.5 W kg^-1 (at 0.5 A g^-1) in a voltage of 1.55 V.

Synthesis of zinc sulfide/copper sulfide/porous carbonized cotton nanocomposites for flexible supercapacitor and recyclable photocatalysis with high performance

The composite material composed of zinc sulfide, copper sulfide and porous carbon is prepared in this study, exhibiting excellent performances in the field of supercapacitor electrode and photocatalysts. In the degradation process of organic pollutants, zinc sulfide/copper sulfide with heterostructure effectively reduce the recombination rate of photo-generated electron-hole pairs. And the porous carbon substrate can not only accelerate the separation of photo-carriers but also provide numerous active sites. Furthermore, the sample can be easily separated after decomposing the organic pollutants. As a supercapacitor electrode, the combination of zinc sulfide/copper sulfide with large pseudo-capacitance and porous carbon material with excellent double-layercapacitance results in superior electrochemical performances. The composite electrode shows a high specific capacitance of 1925 mF cm^-2/0.53 mAh cm^-2 at 4 mA cm^-2. And the symmetric flexible supercapacitor based on the composite electrode achieves an outstanding energy density (0.39 Wh cm^-2 at the power density of 4.32 W cm^-2). Therefore, the zinc sulfide/copper sulfide/porous carbonized cotton nanocomposites (pCZCS) prepared herein exhibit dual functions of photocatalysts with high efficiency as well as energy storage materials with high energy density, which is interesting and important for expanding the practical applications in cross fields.

Green-Synthesized Rice-Shaped Copper Oxide Nanoparticles Using Caesalpinia bonducella Seed Extract and Their Applications

Copper oxide nanoparticles (CuO Nps) were synthesized using Caesalpinia bonducella seed extract via a green synthetic pathway and were evaluated for electrocatalytic properties by carrying out electrochemical detection of riboflavin [vitamin B2 (VB2)]. The seeds of C. bonducella are known to have strong antioxidant properties arising due to the presence of various components, including citrulline, phytosterinin, β-carotene, and flavonoids, which serve as reducing, stabilizing, and capping agents. The synthesized CuO Nps were characterized using UV-visible spectroscopy, Fourier transform infrared spectroscopy, thermogravimetrc analysis-differential thermal analysis, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy and further used as a modifier for a graphite electrode surface. The modified electrode was electrochemically characterized by cyclic voltammetry, square-wave voltammetry, and chronoamperometry techniques and then assessed for electrocatalysis by carrying out the detection of VB2. The electrochemical sensor could be used for nanomolar detection of VB2 with an observed linear range of 3.13-56.3 nM with a limit of detection of 1.04 nM. The electrode showed good stability and reproducibility over a period of 120 days. The CuO Nps were further analyzed for antibacterial effect with Gram-positive and Gram-negative bacteria, and in both cases, high antibacterial activity was clearly observed. The newly synthesized nanoparticles, thus, proved to be an interesting material for electrochemical and biological studies.

Bimetal-organic framework derived Cu(NiCo)2S4/Ni3S4 electrode material with hierarchical hollow heterostructure for high performance energy storage

Rational design of electrical active materials with high performance for energy storage and conversion is of great significance. Herein, Cu(NiCo)₂S₄/Ni₃S₄, a three-dimensional (3D) hierarchical hollow heterostructured electrode material, is designed by etching the well-defined bimetal organic framework (MOF) via sequential in-situ ion-exchange processes. This trimetallic sulfides with unique structure provide large surface area, hierarchical pore distribution and enhanced electrical conductivity, can enrich the active sites for redox reactions, facilitate electrolyte penetration and rapid charge transfer kinetics. As a result, the Cu(NiCo)₂S₄/Ni₃S₄ electrode exhibits a high specific capacitance of 1320 F/g at 1 A/g and excellent rate performance (only 15% of capacitance is attenuated when the current density is increased by 20 times). Furthermore, a fabricated hybrid supercapacitor of Cu(NiCo)₂S₄/Ni₃S₄/AC can deliver a maximum energy density of 40.8 Wh/kg, remarkable power density of 7859.2 W/kg and superior cycling stability (85% retention of capacitance after 5000 cycles), demonstrating great potential for practical applications in energy storage and conversion devices.

An ionic liquid-modified reduced graphene oxide electrode material with favourable electrochemical properties

The supercapacitor assembled by a RGO–IL material showed an outstanding energy density (50.19 W h kg⁻¹) and could light an LED for 30 s.

Engineering thermally activated NiMoO4 nanoflowers and biowaste derived activated carbon-based electrodes for high-performance supercapatteries

NiMoO₄ nanoflowers having pure crystalline phases with slight amorphous surface exhibited excellent battery-like electrochemical performance and potential for supercapattery positive electrodes.