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1.
Mixed valence spinel oxides have emerged as an attractive and inexpensive anode electrocatalyst for water oxidation to replace noble metals based electrocatalysts. The present work demonstrates the facile synthesis of Zn substituted MnCo2O4 supported on 3D graphene prepared by simple hydrothermal technique and its application as an electrocatalyst for water oxidation and methanol oxidation. The physico-chemical properties of the nanocatalyst were studied using various microscopic, spectroscopic and diffraction analyses confirming the formation of the composite. The electrocatalytic performance of the prepared electrocatalyst was evaluated using potentiodynamic, potentiostatic and impedance techniques. The synthesized Zn1-xMnxCo2O4/rGO electrocatalyst with x = 0.2 and 0.4 offered the same onset potential and overpotential at 10 mA/cm2. However, catalyst x = 0.4 delivered a higher current density indicating the superiority of the same over other compositions which is attributed to better kinetics that it possessed for OER as revealed by the smallest Tafel slope (80.6 mV dec−1). The prepared electrocatalysts were tested for methanol oxidation in which electrocatalyst Zn1-xMnxCo2O4/rGO with x = 0.4 shows a better electrochemical performance in oxidizing methanol with the higher current density of 142.3 mA/cm2. The above catalyst also revealed excellent stability and durability during both MOR and OER, suggesting that it can be utilized in practical applications.  相似文献   

2.
In this study, a facile sonochemical strategy is used for the fabrication of CoFe2O4/MWCNTs hybrids as an electrode material for supercapacitor applications. FE-SEM image demonstrates the uniformly well-distributed MWCNTs as well as porous structures in the prepared CoFe2O4/MWCNTs hybrids, suggesting 3D network formation of conductive pathway, which can enhance the charge and mass transport properties between the electrodes and electrolytes during the faradic redox reactions. The as-fabricated CoFe2O4/MWCNTs hybrids with the MWCNTs concentration of 15 mg (CFC15) delivers maximum specific capacitance of 390 F g−1 at a current density of 1 mA cm−2, excellent rate capability (275 F g−1 at 10 mA cm−2), and outstanding cycling stability (86.9% capacitance retention after 2000 cycles at 3 mA cm−2). Furthermore, the electrochemical performance of the CFC15 is superior to those of pure CoFe2O4 and other CoFe2O4/MWCNTs hybrids (CFC5, CFC10 and CFC20), indicating well-dispersion MWCNTs and uniform porous structures. Also, as-fabricated asymmetric supercapacitor device using the CoFe2O4/MWCNTs hybrids as the positive electrode and activated carbon as the negative electrode materials shows the outstanding supercapacitive performance (high specific capacitance, superior cycling stability and good rate capability) for energy storage devices. It delivers a capacitance value of 81 F g−1 at 3 mA cm−2, ca. 92% retention of its initial capacitance value after 2000 charge-discharge cycles and excellent energy density (26.67 W h kg−1) at high power density (~319 W kg−1).  相似文献   

3.
A three-part nano-catalyst including ruthenium oxide, manganese cobalt oxide, and reduced graphene oxide nanosheet in form of RuO2-MnCo2O4/rGO is synthesized by one-step hydrothermal synthesis. The material is placed on a glassy carbon electrode (GCE) for electrochemical studies. The ability of these nano-catalysts in the oxidation process of methanol in an alkaline medium for usage in direct methanol fuel cells (DMFC) was examined with electrochemical tests of cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The effect of the addition of rGO to the nanocatalyst structure in the methanol oxidation reaction (MOR) process was investigated. We introduced the RuO2-MnCo2O4/rGO as a nanocatalyst with excellent cyclic stability of 97% after 5000 cycles in the MOR process. Besides, the study of the Tafel plots and the effect of temperature and scan rate in the MOR process showed that RuO2-MnCo2O4/rGO nanocatalyst has better electrochemical properties than MnCo2O4 and RuO2-MnCo2O4. This high electrocatalytic activity could be related to the synergistic effect of placement of metal oxides of ruthenium, manganese, and cobalt near each other and putting them on rGO, which enhances conductivity and surface area and improve electron transfer. The decrease in the resistance against charge transfer and the increment in the anodic current density illustrated that the reaction rate is enhanced at higher temperature. Thus RuO2-MnCo2O4/rGO shows robust stability and superior performance for MOR.  相似文献   

4.
The structure-activity relationship between the morphology and composition of Pd-based nanocatalysts is an important fundamental issue in direct methanol fuel cells (DMFC). Three dimensional (3D) netlike Pd–Rh bimetallic catalysts with different atomic ratios (Pd1Rh3, PdRh, Pd3Rh1) are synthesized through a simple wet chemical way using P123 as a reducing agent and KBr as morphological regulator. The morphology, structure and composition of the catalysts are proved by a series of physicochemical test technology. It is shown that the 3D-netlike structure is composed of short self-assembly nanochains. Electrochemical results display that their application towards methanol oxidation reaction (MOR) in alkaline solution. The MOR activity of the optimized Pd3Rh1 nanocatalyst is improved to about 4.0 mA cm−2, which is much higher than that of the commercial Pd/C catalyst.  相似文献   

5.
The methanol electro-oxidation (MEO) on Pd–SnO2/MWCNTs catalysts prepared by microwave-assisted polyol reduction method has been investigated. The structure, morphology and electro-catalytic performances of the catalysts were characterized with XRD, TEM and cyclic voltammetry (CV). The results showed that the highly dispersed Pd nano-particles (PdNPs) with a narrow size distribution on MWCNTs were successfully synthesized. The catalytic activity of Pd–SnO2/MWCNTs for MEO was up to 778.8 mA/mg Pd in 0.1 M KOH solution containing 1 M methanol, which was significant higher than that of Pd/C (414.2 mA/mg Pd) or Pd–SnO2/C (566.7 mA/mg Pd). Moreover, the MEO on Pd–SnO2/MWCNTs electrode displayed an irreversible behavior under a diffusion control giving an exchange current density (j0) of 3.76 × 10−4 A cm−2 and a Tafel slope of 149 mV dec−1 (α = 0.56) at 25 °C, which indicates that Pd–SnO2/MWCNTs catalyst has a high electro-catalytic performance for the MEO in alkaline media.  相似文献   

6.
Multi-walled carbon nanotubes (MWCNTs) were used as catalyst support for depositing platinum nanoparticles by a wet chemistry route. MWCNTs were initially surface modified by citric acid to introduce functional groups which act as anchors for metallic clusters. A two-phase (water-toluene) method was used to transfer PtCl62− from aqueous to organic phase and the subsequent sodium formate solution reduction step yielded Pt nanoparticles on MWCNTs. High-resolution TEM images showed that the platinum particles in the size range of 1-3 nm are homogeneously distributed on the surface of MWCNTs. The Pt/MWCNTs nanocatalyst was evaluated in the proton exchange membrane (PEM) single cell using H2/O2 at 80 °C with Nafion-212 electrolyte. The single PEM fuel cell exhibited a peak power density of about 1100 mW cm−2 with a total catalyst loading of 0.6 mg Pt cm−2 (anode: 0.2 mg Pt cm−2 and cathode: 0.4 mg Pt cm−2). The durability of Pt/MWCNTs nanocatalyst was evaluated for 100 h at 80 °C at ambient pressure and the performance (current density at 0.4 V) remained stable throughout. The electrochemically active surface area (64 m2 g−1) as estimated by cyclic voltammetry (CV) was also similar before and after the durability test.  相似文献   

7.
A novel silver oxides oxygen evolving catalyst (Ag-OEC) for hydrogen production by water splitting was formed in situ on an indium tin oxide anode, in a near-neutral potassium tetraborate (K2B4O7) electrolyte. The catalyst exhibited high activity and low overpotential for O2 evolution under mild conditions. The main functional composition of the catalyst was a redox couple of Ag2O/AgO. Catalytic activity during oxygen evolution was evaluated by cyclic voltammetry and Tafel plot. The effects of the concentration, temperature, and pH of K2B4O7 solution on the catalyst, and the Faradaic efficiency of the oxygen evolving reaction were examined. The results show that the Ag-OEC exhibits excellent oxygen evolution properties, with an oxygen evolving overpotential of 318 mV at a current density of 1 mA/cm2.  相似文献   

8.
Thiophene based heterocyclic compounds plays important roles in organic chemistry due to their unexpected properties. Herein, novel benzothiophene derivatives (6A-F) are synthesized via Sonogashira coupling, iodocyclization reaction, Suzuki-Miyaura coupling and condensation reactions. After characterization of design molecules, their glucose electrooxidation activities are investigated. Electrochemical measurements are performed by cyclic voltammetry, chrono amperometry, and electrochemical impedance spectroscopy in 1 M KOH +0.5 M C6H12O6 solution. This results show that the highest performance organic-based catalysts is obtained as 0.729 mA/cm2 (3.345 mA/mg) for the 2-(4-(2-pentylbenzo [b]thiophen-3-yl)benzylidene)malononitrile (6B). Furthermore, 6B catalyst is shown long term stability, the best current density value (1.151 mA cm−2), and the best transfer resistance load between organic-based catalysts. As a result, it is clear that these benzothiophene derivatives are promising organic based catalyst, an alternative to the expensive Pd and Pt based metal catalyst, for direct glucose fuel cell anode.  相似文献   

9.
Mixed Pd–Au bimetallic nanoparticles embedded nitrogen doped graphene composites (PdAu/NG180) are explored for efficient electrocatalytic oxidation of methanol. A simple hydrothermal one-pot polyol method, involving simultaneous reduction of both Pd and Au, is utilized for the synthesis of Pd20-xAux/NG180 (x wt % = 0, 5, 10 and 15). This method is of multiple advantages such as inexpensiveness, reagent-free and environment-friendly being surfactant free. The morphology, crystal structure and chemical composition of NG180, Pd/NG180 and Pd20-xAux/NG180 catalysts are analyzed by XRD, FESEM-EDX, TEM, XPS and Raman spectroscopy methods. Electrocatalytic activities of PdAu/NG180 nanocomposites toward methanol oxidation reaction (MOR) in alkaline media are investigated by cyclic voltammetry, chronoamperometry and CO stripping measurements. Pd20-xAux/NG180 exhibited an increase in the electroactive surface area of Pd to twice by the coexistence of Au. In cyclic voltammetry studies, Pd10Au10/NG180 catalyst exhibits highest peak current density for MOR and is 1.5 times highly efficient compared to Pd20/NG180 with an enhanced shift in the onset potential by 140 mV to lower overpotentials. Besides, Pd10Au10/NG180 catalyst exhibited enhanced electroactive surface area and long-time durability in comparison to Pd20/NG180 catalyst. The steady state current density for MOR observed with Pd10Au10/NG180 at the end of 4000 s (98 mA mg−1Pd) is higher than those observed with all the other catalysts at the end of mere 1000 s alone (97, 61, and 32 mA mg−1Pd). The promising high electrocatalytic activity of Pd10Au10/NG180 is well corroborated from CO stripping experiments that the specific adsorption of CO onto Pd10Au10/NG180 (0.71 C m−2) is merely half to that observed onto Pd20/NG180 (1.49 C m−2).  相似文献   

10.
Development of highly effective and stable electrocatalysts is urgent for various energy conversion applications. Herein, a facile co-reduction approach was developed to fabricate three-dimensional (3D) hyperbranched PtRh nanoassemblies (NAs) under solvothermal conditions, where creatinine and cetyltrimethylammonium chloride (CTAC) were employed as the structure-directing agents. The as-synthesized nanocatalyst exhibited intriguing catalytic characters for hydrogen evolution reduction (HER) with a low overpotential (20 mV) at 10 mA cm−2 and a small Tafel slope (49.01 mV dec−1). Meanwhile, the catalyst showed remarkably enlarged mass activity (MA: 2.16/2.02 A mg−1) and specific activity (SA: 4.16/3.88 mA cm−2) towards ethylene glycol and glycerol oxidation reactions (EGOR and GOR) alternative to commercial Pt black and homemade Pt3Rh nanodendrites (NDs), PtRh3 NDs and Pt nanoparticles (NPs). This method offers a feasible platform to fabricate bifunctional, efficient, durable and cost-effective nanocatalysts with finely engineered structures and morphologies for renewable energy devices.  相似文献   

11.
Nickel ferrite (NiFe2O4) has been explored as a promising oxygen evolution reaction (OER) electrocatalyst for water splitting owning to its earth-abundant and considerable water oxidation catalytic activity. Nevertheless, its practical electrocatalytic performance towards OER is still undesirable due to the sluggish OER kinetics and high overpotential gap on the water oxidation anode side. In this work, in order to enhance the electrochemical water oxidation performance of NiFe2O4, the surface of NiFe2O4 is functionalized with phosphate ions (Pi) by using a facile incipient impregnation and following calcination process. Results demonstrate that the OER properties of NiFe2O4 under alkaline conditions can be dramatically boosted by the surface Pi functionalization. In 1.0 M KOH solution, the resulting NiFe2O4-Pi on glassy carbon (GC) electrode demonstrates quite lower overpotential of 332 mV (10 mA/cm2) and Tafel slope of 57 mV/dec compared to that of pristine NiFe2O4 (443 mV@10 mA/cm2 and 96 mV/dec), which is also better than that of commercial RuO2 electrocatalysts (348 mV@10 mA/cm2 and 80 mV/dec). Moreover, such electrocatalyst on nickel foam electrode also realizes superior OER durability to afford a current density of 70 mA/cm2 at overpotential of only 300 mV for at least 28 h. The excellent electrocatalytic water oxidation activities of NiFe2O4-Pi can be attributed to the tuning electronic property and surface wettability by Pi ions functionalization. This work provides us a novel and effective approach to modify the photo-/electrocatalytic activity for transition metal oxides.  相似文献   

12.
To achieve the practical application of direct methanol fuel cells, it is highly important to develop effective electrocatalyst with high activity and favorable durability. Herein, we report the successful preparation of PtCu bimetallic nanoparticles supported on ceria/multi-walled carbon nanotubes composite (PtCu–CeO2/MWCNTs) via microwave-assisted polyol reduction procedure. The composition and morphology of as-obtained composite catalysts were characterized by X-ray diffraction, Raman, X-ray photoelectron spectra, scanning electron microscopy and transmission electron microscopy. The synergistic effects combining PtCu bimetallic effect and oxygen vacancy effect in ceria of such composite catalysts provide abundant active surface area and enhanced conductivity for the effective charge transport during the methanol oxidation reaction (MOR) process. As a results, the PtCu–CeO2/MWCNTs with optimized Pt proportion achieve greatly enhanced MOR activity with mass activity of 1.28 A mg−1Pt and specific activity of 2.03 mA cm−2, superior CO tolerance and reliable stability in contrast to that of commercial Pt/C catalysts.  相似文献   

13.
To improve oxidation resistance, prevent Cr evaporation and maintain appropriate electrical conductivity of AISI 430 stainless steel (430 SS) as the solid oxide fuel cells' (SOFCs) interconnect, a double-layered Co-Mn-O spinel coating is fabricated successfully on 430 SS via a simple double glow plasma alloying process (DGPA) followed by heating in the air (preoxidation treatment). The double-layered Co-Mn-O spinel coating is composed of a thick MnCo2O4 spinel outlayer and a thin mutual-diffused (MnCoFe)3O4 oxide innerlayer. The isothermal and cyclic oxidation measurements are used to investigate the oxidation resistance, and the ASR test is performed to evaluate the conductivity for the coated and uncoated specimens. The coated specimen has a lower oxidation kinetics rate constant (9.0929 × 10−4 mg2 cm−4 h−1) than the uncoated one (1.900 × 10−3 mg2 cm−4 h−1) and the weight gain of the coated specimen (0.84 mg cm−2) is less than that of bare steel (1.29 mg cm−2) after 750 h oxidation. Meanwhile, the coated specimen holds a lower area specific resistance (0.029 Ω cm2) compared to the uncoated one (2.28 Ω cm2) after 408 h oxidation. Furthermore, the compact Co-Mn-O spinel coating can effectively impede Cr-volatilization. Additionally, the probable mechanism of the Co-Mn alloy conversion into spinel and the electronic conduction behavior in the spinel are discussed. The effects of mutual-diffused oxide innerlayer on oxidation behavior and conductivity are investigated.  相似文献   

14.
Developing catalysts with high performance and low cost for methanol oxidation reaction (MOR) is the key to promoting the industrialization of direct methanol fuel cells (DMFCs). In this work, multiwalled carbon nanotubes (MWCNTs) supported PtCo alloys catalysts with improved MOR properties and anti-CO poisoning ability are successfully prepared by integrating low temperature adsorption and high temperature reduction method. The Pt1Co3@NC/MWCNTs sample with moderate Co2+ feeding content (0.81 mA/ugPt) achieves a factor of 1.93 enhancement in MOR mass activity compared to the commercial Pt/C catalyst (0.42 mA/ugPt). In addition, the Pt1Co3@NC/MWCNTs sample displays a lower CO oxidation onset potential respect to pristine Pt/C catalyst (0.74 V vs. 0.82 V). Scuh improvement of MOR activity, durability and anti-CO poisoning ability of the Pt1Co3@NC/MWCNTs catalyst is ascribed to the moderate surface compositions, optimal electronic interaction between PtCo alloys and MWCNTs, and the protection of N-doped carbon (NC) shells. This study provides a new direction to decrease the utilization of platinum and improve the MOR activity, stability and anti-CO poisoning ability of electrocatalysts which will be potential in design and fabrication of the highly efficient electrocatalysts for DMFCs applications.  相似文献   

15.
In this paper, we have successfully prepared MnNi2O4 micro/nano multiporous spheres via a subsequent simple impregnation and calcination. Lithium storage performance of the as-prepared MnNi2O4 has been firstly investigated, with a stable capacity of 669.2 mAh g?1 after 70 cycles at 1.0 A g?1. Cyclic voltammograms data indicate that discharge-charge process is synergistically controlled by both the dominate diffusion and the secondary capacitive behavior. Electrochemical impedance spectroscopy evidences low resistance and high Li+ diffusion coefficient (3.4 × 10?15 cm2 s?1). Furthermore, an excellent supercapacitor behavior is also achieved. All that can be benefited from the unique micro/nano multiporous structures which can effectively facilitate electrolyte penetration and diffusion of tiny particles, alleviate the volume swelling and the electrochemical agglomeration, suggesting a prospective application in energy storage devices.  相似文献   

16.
The multi-walled carbon nanotubes (MWNTs) are introduced as reductants to prepare bimetallic PtNix composite nanocatalysts via a hydrothermal reaction for the investigation of ethanol oxidation reaction (EOR). The crystal structure and elemental analysis of PtNix/MWNTs nanocatalysts are characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS), respectively. The morphologies of these nanocatalysts are observed by transmission electron microscopy (TEM) and scanning electron microscope (SEM). The results reveal that the PtNix nanocatalysts with a nanoparticle size ranging from 6 to 13 nm are immobilized on the surface of MWNTs. The electrocatalytic activities of the PtNix/MWNTs nanocatalysts for EOR in alkaline media are examined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). The onset potential of EOR in the nanocatalyst of PtNi3/MWNTs is negatively shifted for about 190 mV as compared to that in the nanocatalyst of Pt/MWNTs. The current for the forward anodic peak of EOR in the PtNi3/MWNTs nanocatalyst is about 2.5 times higher than that of pure Pt/MWNTs.  相似文献   

17.
18.
Carbon nanomaterials that are electrochemically bifunctional and active in supercapacitor and hydrogen-evolution-reaction (HER) applications have attracted recent research attention. We have prepared porous carbon spheres - doped Ni, Co - alloys by using a hydrothermal method with melamine and pectin as precursors and with the addition of nickel nitrate and cobalt nitrate. The corresponding materials exhibit good electrochemical performance and excellent electrocatalytic activity for HER. The overpotential (OP) of the as-prepared materials can achieve 240 mV keeping a Tafel slope (TS) of 55 mV dec−1 at 10 mA cm−2 in an acid (0.5 M H2SO4) solution. The corresponding samples maintain stability after 24 h and 5000 cycles in the chronovoltage and cyclic voltammetry methods, respectively. When the as-prepared materials are oxidized by 30% H2O2 for 12 h, the corresponding as-prepared oxidation samples exhibit excellent electrochemical performance in a supercapacitor application. The specific capacitance (SC) of the as-obtained materials reaches 312 F g−1 at 1 A g−1 with decent rate capability and cyclic stability. This work provides new applications for bifunctional electrochemically active materials.  相似文献   

19.
The development of cost-effective, highly efficient and robust electrodes for oxygen evolution reaction (OER) is greatly significant for water-electrolysis to produce hydrogen. In this paper, we report a stainless steel fiber felt (SSF) electrode with greatly enhanced OER catalytic performance and durability. The SSF is directly treated by cyclic voltammetry (CV) method in alkaline electrolyte, which is more facile and convenient than the traditional measures. The characterization results of X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy indicate that an ultra-thin layer composed of Fe/Ni/Cr hydroxides/oxides with 3D open nanoporous structure is formed on the surface of SSF after CV treatment. The electrochemical tests show that the prepared SSF electrode displays a very low overpotential of 230 mV at 10 mA cm−2, a small Tafel slope of 44 mV dec−1 and good long-term durability of 550 h in 1 M KOH. The excellent OER performance of SSF electrode is contributed to the formation of hybrid metal hydroxides/oxides on its surface via in situ self-growth by electrochemical induction. Furthermore, the electrode only requires an overpotential of 340 mV at 10 mA cm−2 in 0.5 M Na2CO3/NaHCO3 solution. It is expectable that the modified SSF will be a promising catalysis electrode for water-electrolysis in large-scale commercial production.  相似文献   

20.
Here, the Ni-based metallic nano-particles (Ni, NiMo and NiMoP) were electrodeposited on/in the surface of ERGO/CE substrate from a citrate-based electrolyte and their catalytic activities investigated towards methanol and ethanol electro-oxidation. The physicochemical characterizations of all prepared electrocatalysts were investigated by different electrochemical and non-electrochemical techniques. The electrocatalytic activities of the modified electrodes towards the electro-oxidation of methanol and ethanol were studied in 0.1 M NaOH solution by conventional electrochemical methods such as cyclic voltammetry and chronoamperometry. In the optimized electrodeposition conditions, the obtained electrochemical results indicate that the NiMoP/ERGO/CE displays dramatically improved electrocatalytic activity [Jpf (mA.cm−2) = 263.14 for methanol and Jpf (mA.cm−2) = 253.35 for ethanol], stability and poisoning tolerance towards the electro-oxidation of these fuels in alkaline solution. Finally, for comparison, the Ni (alone) and NiMo (binary) electrodeposited on/in the ERGO/CE (without P) and also studying the influence of the ERGO layers on the surface of CE, the NiMoP/CE (without ERGO) were prepared and applied as electrocatalysts.  相似文献   

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