Precious non-noble metals have been constantly attracting research attention in order to realize an inexpensive, extra active and more stable electrocatalysts in terms of various oxidation states and structures for their applications in oxidation (splitting) of water. In the present work graphene oxide incorporated, MnO2-NiO composite metal oxide nanoflakes were synthesized on the stainless steel substrate using efficient electrodeposition route in alkaline media and drop casting method with further annealing treatment at 400 °C for 4 h. Initially MnO2-NiO nanoflakes were deposited using different cyclic sweep rates, later graphene oxide suspension was drop casted on the MnO2-NiO nanoflakes and subsequently subjected to annealing at 200 °C for 2 h. The prepared electrode material is denoted as GO/MnO2-NiO/SS and used as an electrocatalyst for oxygen evolution. Field emission scanning electron microscopy, transmission electron microscopy, Energy dispersive electron spectroscopy and X-ray diffraction spectroscopy were used to study the crystalline nature and morphologies of the deposited films. The electrochemical properties of the electrode material were investigated using cyclic voltammetry and linear sweep voltammetry. The electrode exhibits low overpotential and small Tafel slope of 379 mV and 47.84 mVdec−1 at the current density of 10 mA cm−2 in alkaline (KOH) medium. In addition, the electrode shows a long time stability of 28800 s. Hence, the present study suggests that the GO incorporated Mn-Ni bimetal oxide modified electrode is suitable electrode material for oxygen evolution reaction (OER), owing to its facile preparation, inexpensive, easy handling and high active nature. 相似文献
Ti(OH)4 and TiCl4 modified bentonite (Ti–Na-bent) were applied in the removal of Th(IV) from aqueous solution. Effect of different factors such as pH, contact time, temperature, initial concentration of Th(IV) and efficiency of them for thorium adsorption are investigated. Ti–Na-bent showed high adsorption capacity (qm?=?231.37 mg/g) and quick adsorption kinetics at lower pH. The adsorption mechanisms involved are: (1) Th4+, [Th(OH)4?n]n+ complexed on the outer-sphere of Na-bent and Ti–Na-bent. (2) Ion exchange between Th4+, [Th(OH)4?n]n+ and exchangeable cations of Na-bent and the H on the hydroxyl group of Ti(OH)4. Ti–Na-bent manifested high adsorption capacity for Th(IV), good acid resistance and long-term adsorption stability.
The wide use of lithium ion batteries (LIBs) has created much waste, which has become a global issue. It is vital to recycle waste LIBs considering their environmental risks and resource characteristics. Anode graphite from spent LIBs still possess a complete layer structure and contain some oxygen-containing groups between layers, which can be reused to prepare high value-added products. Given the intrinsic defect structure of anode graphite, copper foils in LIB anode electrodes, and excellent properties of graphene, graphene oxide–copper composite material was prepared in this work. Anode graphite was firstly purified to remove organic impurities by calcination and remove lithium. Purified graphite was used to prepare graphene oxide–copper composite material after oxidation to graphite oxide, ultrasonic exfoliation to graphene oxide (GO), and Cu2+ adsorption. Compared with natural graphite, preparing graphite oxide using anode graphite consumed 40% less concentrated H2SO4 and 28.6% less KMnO4. Cu2+ was well adsorbed by 1.0 mg L?1 stable GO suspension at pH 5.3 for 120 min. Graphene oxide–copper composite material could be successfully obtained after 6 h absorption, 3 h bonding between GO and Cu2+ with 3/100 of GO/CuSO4 mass ratio. Compared to CuO, graphene oxide–copper composite material had better catalytic photodegradation performance on methylene blue, and the electric field further improved the photodegradation efficiency of the composite material. 相似文献
In this paper, three-dimensional graphene (3DG) electrode material was prepared by hydrothermal reduction using graphene oxide as precursor. Its morphology and structure were characterized by SEM, BET, XRD, Raman, FTIR and TG, and its electrochemical performance was also measured. The results showed that 3DG possessed hierarchical pore structure, large specific surface area, high specific capacitance and low impedance. Using 3DG as electrode material for electrosorption of UO22+, it showed that the saturated adsorption capacity can reach up to 113.80 mg g?1 and the adsorption rate is 0.32 mg g?1 min?1 at a given optimal applied voltage of 1.8 V.
The present work is about the preparation of silver (Ag)-doped manganese oxide (MnO2)/graphene oxide (GO) composite thin films are deposited by a facile and binder-free successive ionic layer adsorption and reaction (SILAR) method for the first time. The Brunauer-Emmett-Teller (BET) study revealed the nanosheets of MnO2–Ag3/GO exhibit high specific surface area of 192 m2 g?1. The tailored flower-like morphology and interconnected nanosheets of MnO2–Ag3/GO electrodes achieved high electrochemical performance. The maximum specific capacitance (Cs) of 877 F g?1 at the scan rate of 5 mV s?1 is obtained for MnO2–Ag3/GO electrode tested in 1 M sodium sulfate (Na2SO4) electrolyte with capacity retention of 94.57% after 5000 cycling stability. The MnO2–Ag3/GO composite-based flexible solid state symmetric supercapacitor (FSS-SSC) device delivered Cs as 164 F g?1 with specific energy of 57 Wh kg?1 at specific power of 1.6 kW kg?1 and capacitive retention of 94% after 10,000 cycles. 相似文献
A new prompt room temperature synthetic route to 2D nanostructured metal oxide–graphene‐hybrid electrode materials can be developed by the application of colloidal reduced graphene oxide (RGO) nanosheets as an efficient reaction accelerator for the synthesis of δ‐MnO2 2D nanoplates. Whereas the synthesis of the 2D nanostructured δ‐MnO2 at room temperature requires treating divalent manganese compounds with persulfate ions for at least 24 h, the addition of RGO nanosheet causes a dramatic shortening of synthesis time to 1 h, underscoring its effectiveness for the promotion of the formation of 2D nanostructured metal oxide. To the best of our knowledge, this is the first example of the accelerated synthesis of 2D nanostructured hybrid material induced by the RGO nanosheets. The observed acceleration of nanoplate formation upon the addition of RGO nanosheets is attributable to the enhancement of the oxidizing power of persulfate ions, the increase of the solubility of precursor MnCO3, and the promoted crystal growth of δ‐MnO2 2D nanoplates. The resulting hybridization between RGO nanosheets and δ‐MnO2 nanoplates is quite powerful not only in increasing the surface area of manganese oxide nanoplate but also in enhancing its electrochemical activity. Of prime importance is that the present δ‐MnO2–RGO nanocomposites show much superior electrode performance over most of 2D nanostructured manganate systems including a similar porous assembly of RGO and layered MnO2 nanosheets. This result underscores that the present RGO‐assisted solution‐based synthesis can provide a prompt and scalable method to produce nanostructured hybrid electrode materials. 相似文献
In this study, to improve the specific capacitance of graphene-based supercapacitor, novel quadri composite of G/PPy/MnOx/Cu(OH)2 was synthesized by using a facile and inexpensive route. First, a two-step method consisting of thermal decomposition and in situ oxidative polymerization was employed to fabricate graphene/polypyrrole/manganese oxide composites. Second, Cu(OH)2 nanowires were deposited on Cu foil. Afterwards, for the electrochemical measurements, composite powders were deposited on Cu(OH)2/Cu foil substrate as working electrodes. The synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. The XRD analysis revealed the formation of PPy/graphene, Mn3O4/graphene, and graphene/polypyrrole/MnOx. In addition, the presence of polypyrrole and manganese oxides was confirmed using FT-IR and Raman spectroscopies. Graphene/polypyrrole/MnOx/Cu(OH)2 electrode showed the best electrochemical performance and exhibited the largest specific capacitance of approximately 370 F/g at the scan rate of 10 mV/s in 6 M KOH electrolyte. In addition, other electrochemical measurements (charge–discharge, EIS and cyclical performance) of the G/Cu(OH)2, G/PPy/Cu(OH)2, G/Mn3O4/Cu(OH)2, and G/PPy/MnOx/Cu(OH)2 electrodes suggested that the G/PPy/MnOx/Cu(OH)2 composite electrode is promising materials for supercapacitor application. 相似文献
Titanate nanotubes (TNTs) have attracted great interest in multidisciplinary study since their discovery. The adsorption of thorium [Th(IV)] onto TNTs in the absence and presence of humic acid (HA)/fulvic acid (FA) was studied by batch technique. The influence of pH from 2.0 to 10.0, ionic strength from 0.001 to 0.1 mol L?1 NaClO4, and coexisting electrolyte cations (Li+, Na+, K+) and antions (ClO4?, NO3?, Cl?) on the adsorption of Th(IV) onto TNTs was tested. The adsorption isotherms of Th(IV) was determined at pH 3.0 and analyzed with Langmuir and Freundlich adsorption models, respectively. The results demonstrated that the adsorption of Th(IV) onto TNTs increases steeply with increasing pH from 2.0 to 4.0. Generally, HA/FA was showed to enhance Th(IV) adsorption onto TNTs at low pH values, but to reduce Th(IV) adsorption onto TNTs at high pH values. The adsorption of Th(IV) onto TNTs was also dependent on coexisting electrolyte ions in aqueous solution under our experimental conditions. The adsorption of Th(IV) onto TNTs is exothermic and spontaneous. The findings indicating that TNTs can be used as a promising candidate for the enrichment and solidification of Th(IV) or its analogue actinides from large volume solution in real work. 相似文献
MnO2/graphene nanocomposites with different morphologies were synthesized and the petal‐shaped nanosheet MnO2/graphene composite was developed as an electrode material for nonenzymatic hydrogen peroxide (H2O2) sensor. The morphology, structure, composition, and hydrophilicity of the resulting products were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and the contact angle tests. In addition, the fabricated MnO2/graphene composites could be used as catalysts for the electrochemical oxidation of H2O2. Cyclic voltammogram (CV) experiments indicated that MnO2/graphene‐modified electrode showed good electrocatalytic activity towards both the oxidation and reduction of H2O2 in a neutral environment. Amperometric response results illustrated that this nonenzymatic sensor had excellent anti‐interference ability and displayed two linear ranges from 10 to 90 µM and from 0.2 to 0.9 mM with a detection limit of 2 µM. 相似文献
Nanocomposite materials have been successfully applied to remediation of organic and inorganic contaminants from polluted water. The present study investigates the synthesis, characterizations, and adsorptive performances of graphene oxide/SiO2 nanocomposite-based adsorbent. Graphene oxide/SiO2 was used for the adsorption of methylene blue (MB) and Cr (VI) ion from wastewater. Furthermore, the antibacterial activity performance of synthesized nanocomposite was studied. The adsorption consideration has been performed by various adsorption parameters in our laboratory. X-ray crystallography (XRD), Scanning electron microscope (SEM), Energy Dispersive X-ray Analysis (EDX) and, thermal gravimetric analysis (TGA) methods were applied in the characterization, morphological structure, crystallinity, and thermal stability of graphene oxide/SiO2. Maximum capacities of adsorption of graphene oxide/SiO2-based adsorbent had been evaluated by the Langmuir isotherm model for MB and Cr (VI) ion as 555.50 and 181.81 mg/g, respectively. Generally, adsorption experiments revealed that the performances of graphene oxide/SiO2 nanocomposite for all adsorbents have been found in the order MB > Cr (VI). Furthermore, antibacterial activity study against gram-positive and gram-negative bacteria showed and proved that graphene oxide/SiO2 composite showed a remarkable ability to kill bacteria. 相似文献
A new electrocatalyst, MnO2/graphene oxide hybrid nanostructure was successfully synthesized for the nonenzymatic detection of H2O2. The morphological characterization was examined by scanning electron microscopy and transmission electron microscopy. The MnO2/graphene oxide based electrodes showed high electrochemical activity for the detection of H2O2 in alkaline medium. The nonenzymatic biosensors displayed good performance along with low working potential, high sensitivity, low detection limit, and long-term stability, which could be attributed to the high surface area of graphene oxide providing for the deposition of MnO2 nanoparticles. These results demonstrate that this new nanocomposite with the high surface area and electrocatalytic activity offers great promise for new class of nanostructured electrode for nonenzymatic biosensor and energy conversion applications. 相似文献
The adsorption efficiency of a biomass by-product (olive cake) regarding the removal of radium (226Ra) from aqueous solutions has been investigated prior and after its chemical treatment. The chemical treatment of the biomass by-product included phosphorylation and MnO2-coating. The separation/removal efficiency has been studied as a function of pH, salinity (NaCl) and calcium ion concentration (Ca2+) in solution. Evaluation of the experimental data shows clearly that the phosphorylated biomass by-product presents the highest adsorption capacity and efficiency followed by the MnO2-coated material and the non-treated biomass by-product. However, regarding the effect of salinity and the presence of competitive cations (e.g. Ca2+) on the adsorption/removal efficiency, the MnO2-coated material shows the lowest decline in efficiency (only 2 % of the relative adsorption efficiency) followed by the non-treated and the phosphorylated biomass by-product. The results of the present study indicate that depending on the physicochemical characteristics of the radium-contaminated water, all three types of the biomass by-product could be effectively used for the treatment of radium-contaminated waters. Nevertheless, the MnO2-coated material is expected to be the most effective adsorbent and an alternative to MnO2 resins for the treatment of environmentally relevant waters. 相似文献
Electrochemical reduction of CO2 (CO2RR) to value-added chemicals is an attractive strategy for greenhouse gas mitigation and carbon recycle. Carbon material is one of most promising electrocatalysts but its product selectivity is limited by few modulating approaches for active sites. Herein, the predominant pyridinic N-B sites (accounting for 80% to all N species) are fabricated in hierarchically porous structure of graphene nanoribbons/amorphous carbon. The graphene nanoribbons and porous structure can accelerate electron and ion/gas transport during CO2RR, respectively. This carbon electrocatalyst exhibits excellent selectivity toward CO2 reduction to CH4 with the faradaic efficiency of 68% at −0.50 V vs. RHE. As demonstrated by density functional theory, a proper adsorbed energy of *CO and *CH2O are generated on the pyridinic N-B site resulting into high CH4 selectivity. Therefore, this study provides a novel method to modulate active sites of carbon-based electrocatalyst to obtain high CH4 selectivity. 相似文献
Single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and graphene have been tested as carbon allotropes for the modification of carbon screen-printed electrodes (CSPEs) to simultaneously determine melatonin (MT) and serotonin (5-HT). Two groups of CSPEs, both 4 mm in diameter, were explored: The first includes commercial SWCNT, MWCNT and graphene, the second includes SWCNT, MWCNT, graphene oxide nanoribbons and reduced nanoribbons that were drop casted on the electrodes. The carbon nanomaterials enhanced the electroactive area in the following order: CSPE
Carbon nanomaterials on screen-printed electrodes: smart electrochemistry for fast, simultaneous and reliable detection of serotonin the molecule of happiness and melatonin the molecule of darkness.
In order to achieve the degradation of Congo red dye in wastewater, a new type of three-dimensional porous composite catalyst PW7Mo3Cu2/PANI/MnO2 was prepared by using heteropoly acid [TBA]4H3[PW7Mo3Cu2O38(H2O)2] doped intermediate PANI/MnO2. Using IR, UV, SEM, XPS and other characterization techniques, it was confirmed that the heteropoly acid [TBA]4H3[PW7Mo3Cu2O38(H2O)2] was successfully doped into the intermediate PANI/MnO2 to form a three-dimensional porous structure. The results of N2 adsorption–desorption experiment indicated that the composite catalyst belongs to the type IV (a) mesoporous structure material and has a large pore size and specific surface area. Then, the composite catalyst PW7Mo3Cu2/PANI/MnO2 was used to photocatalyze the degradation of Congo red dye. Under the best photocatalytic conditions, the decolorization rate of Congo red dye reached 93.84%. After recovering and repeating the photocatalysis experiment three times, the decolorization rate of Congo red dye was 73.18%. The experimental results proved that the novel composite catalyst has a strong ability to degrade Congo red dye and reusability, and has potential application value.
We describe a novel magnetic nanosorbent that consists of nanowires consisting of a core of metallic iron and an iron (III) oxide shell. These nanowires were then deposited on graphene oxide to form a composite of the type Fe@Fe2O3/GO. Specifically, the magnetic composite is formed via electrostatic interaction between negatively charged GO nanosheets and positively charged Fe@Fe2O3 nanowires in aqueous solution. The material was successfully applied to the extraction of the endocrine-disrupting phenols bisphenol A, triclosan and 2,4-dichlorophenol from water samples. Compared to neat graphene oxide, the composite material exhibits improved properties in terms of microextraction where both the hydrophilic graphene oxide and the Fe@Fe2O3 nanowires participate in the adsorption of the hydrophilic analytes. The amount of adsorbent, pH of water sample, extraction time and desorption time, type and volume of desorption solution were optimized. Following extraction for the absorbent, the phenols were quantified by HPLC. The three phenols can be determined in 0.5 to 100 ng∙mL−1 concentration range, with limits of detection (at an S/N ratio of 3) ranging from 0.08 to 0.10 ng∙mL−1. The repeatability was investigated by evaluating the intra- and inter-day precisions with relative standard deviations of lower than 7.5 % (n = 5). The recoveries from spiked real water samples were in the range from 84.8 to 92.0 %. The results indicate that the novel material can be successfully applied to the extraction and analysis of phenols from water samples.
Scheme 1 procedure for the synthesis of Fe@Fe203/G0
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