首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 250 毫秒
1.
New nanostructured carbons have been developed through pyrolysis of organic aerogels, based on supercritical drying of cellulose acetate gels. These cellulose acetate-based carbon aerogels (CA) are activated by CO2 at 800 °C and impregnated by PtCl62−; the platinum salt is then chemically or electrochemically reduced. The resulting platinized carbon aerogels (Pt/CA) are characterized with transmission electron microscopy (TEM) and electrochemistry. The active area of platinum is estimated from hydrogen adsorption/desorption or CO-stripping voltammetry: it is possible to deposit platinum nanoparticles onto the cellulose acetate-based carbon aerogel surface in significant proportions. The oxygen reduction reaction (ORR) kinetic parameters of the Pt/CA materials, determined from quasi-steady-state voltammetry, are comparable with that of Pt/Vulcan XC72R. These cellulose acetate-based carbon aerogels are thus promising electrocatalyst support for PEM application.  相似文献   

2.
The electrochemical activity and thermal stability of the Pt/TiO2-C were evaluated in the oxygen reduction reaction (ORR) in acid medium at different temperatures. The platinum was selectively deposited onto the TiO2 (Ebg = 2.3 eV) by the photo-irradiation of platinum precursor (Pt4+→Pt0). The Pt/TiO2-C electrocatalyst prepared was characterized by XRD, TEM/EDS, cyclic and lineal voltammetry techniques. TEM images indicated that platinum nanoparticles (<5 nm) were deposited in agglomerates form around the oxide sites. EDS and XRD results confirm the composition and crystalline structure of Pt/TiO2-C. The thermal stability and electrochemical activity of the Pt/TiO2-C for ORR at different temperatures (298–343 K) is higher than Pt/C commercial sample (Pt-Etek). A more favorable apparent enthalpy of activation for Pt/TiO2-C was greatly influenced by addition of oxide in the catalyst compare to Pt-Etek. Single H2/O2 fuel cell performance results of Pt/TiO2-C show an improvement of the power density with the increase of the temperature.  相似文献   

3.
Transition metal carbide catalysts are the alternative products of traditional noble metal Pt/C in oxygen reduction reaction (ORR). Oleic acid-coated iron oxide nanoparticles (F3O4@OA) was prepared by pyrolysis, assembled with reduced graphene oxide (rGO), and carbonized at 800 °C to obtain N doped iron carbide nanoparticles supported rGO (N–Fe3C/rGO). The particle size of nanocrystals increases significantly with the graphene loading risen can be seen in the transmission electron microscope (TEM) image which roughly distributed around 40 nm. The linear scanning voltammetry (LSV) curve shows the material has an ORR performance equivalent to Pt/C in alkaline media.  相似文献   

4.
Hierarchically porous materials are promising as catalyst supports in fuel cells and batteries as they increase overall mass transfer and active site density. In this work, a hierarchically porous catalyst support for oxygen reduction reaction (ORR) in acidic media has been developed by a bottom-up approach. Graphene oxide (GO) was introduced during synthesis conditions of zeolitic imidazolate framework-8 (ZIF-8) to produce hybrid material of ZIF-8/GO. Successful nanocomposite formation was realized by preserved crystallinity and chemical interaction between species as revealed by X-ray diffraction and Fourier transform infrared spectroscopy. Introduction of GO and pyrolysis of resulting hybrid structure causes emergence of disordered meso/macropores with an accompanying increase in pore volume as revealed by N2 sorption experiments. Pt nanoparticle deposition on pyrolyzed hybrid material by polyol method results in electrocatalyst Pt/NC-1, which shows greatly improved mass activity (182 vs 86 A g−1Pt) and specific activity (467 vs 186 μA g−1Pt) at 0.8 V for ORR against reference electrocatalyst Pt/r-GO and improved specific activity against Pt/C.  相似文献   

5.
Enhancement in durability of electrocatalyst is still one of the most important issues in polymer electrolyte fuel cells (PEFCs). Here, we report a structurally coated electrocatalyst supported on carbon nanotubes (CNT), in which platinum (Pt) nanoparticles are coated by nitrogen doped carbon (NC) layers. CNT/NC/Pt/NC shows comparable electrochemical surface area (ECSA) and oxygen reduction reaction (ORR) activity to the non-coated electrocatalyst (CNT/NC/Pt), indicating that NC layer on Pt nanoparticles almost negligibly affects the activities of electrocatalyst; while, CNT/NC/Pt/NC exhibits a higher Pt stability due to the unique structure, in which the Pt nanoparticles are stabilized by the NC layers and Pt aggregation is decelerated proved by TEM measurement. Maximum power density of CNT/NC/Pt/NC reached 604 mW cm?2 with Pt loading of 0.1 mgPt cm?2, which only decreases by 7% compared to CNT/NC/Pt (650 mW cm?2). The electrochemical analysis and fuel cell test illustrate that NC layer on Pt nanoparticles enhances the durability without serious deterioration of fuel cell performance.  相似文献   

6.
In order to seek heterogeneous electrocatalyst with efficient catalytic activity for oxygen reduction reaction (ORR), Fe3O4-CNx composite reported in our previous work was studied as electrocatalyst for ORR and showed poor catalytic activity. To improve the catalytic activity, Fe3O4-CNx composite is modified by the CNx layers derived from lysine through pyrolysis. The physical characterization show that the coral-shaped morphology of the resultant composite (Fe3O4-CNx-Lys) is still retained, while the degree of its graphitic crystalline increases. Besides, Fe3O4-CNx-Lys has 364.7 m2 g−1 of surface area with hierarchical porous structure. Electrochemical tests show that the catalytic activity Fe3O4-CNx-Lys for ORR is not only higher than those Fe3O4-CNx, XC-72-Lys derived from lysine and XC-72 Vulcan carbon but also comparable to that of commercial Pt/C (20 wt%).  相似文献   

7.
In this paper, a noble-metal-free electrocatalyst based on carbon-supported zirconium oxynitride (ZrOxNy/C) was prepared by ammonolysis of carbon-supported zirconia (ZrO2/C) at 950 °C and investigated as cathode electrocatalyst towards oxygen reduction reaction (ORR) in PEMFCs. The electrocatalyst was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The catalytic activity of the catalyst towards ORR was investigated by using the rotating disk electrode (RDE) technique in an O2-saturated 0.5 M H2SO4 solution. The ZrOxNy/C electrocatalyst presented attractive catalytic activity for ORR. The onset potential of ZrOxNy/C electrocatalyst for oxygen reduction was 0.7 V versus RHE and the four-electron pathway for the ORR was achieved on the surface of ZrOxNy/C electrocatalyst. The ZrOxNy/C electrocatalyst showed a comparatively good cell performance to ORR in PEMFCs, especially when operated at a comparatively high temperature.  相似文献   

8.
Exploring cost-effective electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) have been a goal in the sustainable hydrogen-based society. Although abundant of alternative materials have been developed, Pt/C remains the most efficient electrocatalyst for the ORR and HER. Nevertheless, improving the stability and reducing Pt loading for Pt-based electrocatalysts are still big challenges. Herein, semiconductor crystals Na4Ge9O20 with richer topology structure was chosen as electrocatalyst support, subsequently, the conductive polymer polyaniline (PANI) was decorated on semiconductor Na4Ge9O20, low-content Pt nanoparticles (Pt NPs) with the size of 1–3 nm were then uniformly anchored on the surface of Na4Ge9O20-PANI to obtain the efficient bifunctional electrocatalyst for ORR and HER in the acidic solution. More importantly, the stability and mass activity of the obtained electrocatalyst 5 wt% Pt/Na4Ge9O20-PNAI are significantly higher than that of commercial 20 wt% Pt/C for ORR and HER. It was proposed that the PANI could not only promote the electron transfer from Na4Ge9O20 to Pt, but also stabilize the Pt NPs, thus, improving the electrocatalytic activity and stability of 5 wt% Pt/Na4Ge9O20-PNAI.  相似文献   

9.
High-performance, non-precious metal electrocatalysts have been widely considered among the most prospective candidates to replace Pt-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. Herein, we report a synthetic method, involving templating, polymerization and pyrolysis, that produces catalytically active iron carbide (Fe3C) nanoparticles-loaded porous N-doped carbon materials from polyaniline- and Fe(III)-modified mesoporous graphitic carbon nitride (g-C3N4). We also show that the resulting noble metal-free materials exhibit good electrocatalytic activity for ORR, with good onset and half-wave potentials, in O2-saturated alkaline solution. The structure, composition, crystallinity, and electrocatalytic activity of these materials are found to depend on the pyrolysis temperature and the specific components in the precursor. In particular, the material obtained by pyrolysis at 1000 °C, named Fe3C/NC-1000, shows excellent electrocatalytic activity and better performance, in terms of both onset and half-wave potentials, than Pt/C (20 wt% Pt). The material also tolerates the methanol crossover reaction better than Pt/C and shows negligible shift in onset and half-wave potentials to negative values even after use in 3000 cycles of electrocatalysis. This robust, non-noble metal-based carbon material can potentially become a viable alternative to precious metal electrocatalysts for ORR.  相似文献   

10.
Developing non-precious metal-based catalysts as the substitution of precious catalysts (Pt/C) in oxygen reduction reaction (ORR) is crucial for energy devices. Herein, a template and organic solvent-free method was adopted to synthesize Fe, B, and N doped nanoflake-like carbon materials (Fe/B/N–C) by pyrolysis of monoclinic ZIF-8 coated with iron precursors and boric acid. Benefiting from introducing B into Fe–N–C, the regulated electron cloud density of Fe-Nx sites enhance the charge transfer and promotes the ORR process. The as-synthesized Fe/B/N–C electrocatalyst shows excellent ORR activity of a half-wave potential (0.90 V vs 0.87 V of Pt/C), together with superior long-term stability (95.5% current density retention after 27 h) in alkaline media and is even comparable to the commercial Pt/C catalyst (with a half-wave potential of 0.74 V vs 0.82 V of Pt/C) in an acidic electrolyte. A Zn-air battery assembled with Fe/B/N–C as ORR catalyst delivers a higher open-circuit potential (1.47 V), specific capacity (759.9 mA h g?1Zn at 10 mA cm?2), peak power density (62 mW cm?2), as well as excellent durability (5 mA cm?2 for more than 160 h) compared to those with commercial Pt/C. This work provides an effective strategy to construct B doped Fe–N–C materials as nonprecious ORR catalyst. Theoretical calculations indicate that introduction of B could induce Fe-Nx species electronic configuration and is favorable for activation of OH1 intermediates to promote ORR process.  相似文献   

11.
The catalytic activity of Pt-W electrocatalysts towards oxygen reduction reaction (ORR) was studied. Pt-W/C materials were prepared by thermolysis of tungsten and platinum carbonyl complexes in 1-2 dichloro-benzene during 48 h. The precursors were mixed to obtain relations of Pt:W: 50:50 and 80:20%w, respectively. The Pt carbonyl complex was previously synthesized by bubbling CO in a chloroplatinic acid solution. The synthesized materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV) and a rotating disk electrode (RDE). The results show that both materials (Pt50W50/C and Pt80W20/C) have a crystalline phase associated with metallic platinum and an amorphous phase related with tungsten and carbon. The particle size of the electrocatalysts depends on the relationship between platinum and tungsten. Finally, both materials exhibit catalytic activity for oxygen reduction.  相似文献   

12.
《Journal of power sources》2006,155(2):161-166
The activity for the oxygen reduction reaction (ORR) on carbon supported Pt–Ni electrocatalysts prepared by reduction of Pt and Ni precursors with NaHB4 was investigated in sulphuric acid both in the absence and in the presence of methanol and compared with that of a commercial Pt/C electrocatalyst. In methanol-free sulphuric acid solution the Pt70Ni30/C alloy electrocatalyst showed a lower specific activity towards oxygen reduction compared to Pt/C. In O2-free H2SO4 the onset potential for methanol oxidation on Pt70Ni30/C was shifted to more positive potentials, which indicates a lower activity for methanol oxidation than platinum. In the methanol containing electrolyte the higher methanol tolerance of the Pt70Ni30/C electrocatalyst for the ORR was ascribed to the lower activity of the binary electrocatalyst for methanol oxidation, arising from a composition effect.  相似文献   

13.
A platinum/carbon nanofiber (Pt/CNF) nanocomposite with a platinum loading of 15 wt% is prepared by a modified electrophoretic deposition (EPD) method, and the as-grown nanocomposite is used as the electrocatalyst for oxygen reduction reaction (ORR). For comparison, a Pt/CNF composite with 40 wt% platinum loading is prepared by chemical reduction. High resolution transmission electron microscope (HRTEM) images show that the size of platinum nanoparticles formed by EPD is about 1 nm, much smaller than those by chemical reduction (about 3–5 nm). Cyclic voltammetric analysis in a nitrogen saturated electrolyte shows that the electrochemical surface area of electrocatalyst by EPD is larger than that by chemical reduction. Moreover, although the electrocatalyst prepared by chemical reduction has a higher electrochemical capacity, it is less active than that prepared by EPD. Analysis of the electrode kinetics using Tafel plot suggests that the electrocatalyst prepared by EPD provides a strong ORR activity. Cyclic voltammetric measurements at different scan rates confirm that the ORR on the nanocomposites prepared by EPD is a diffusion-controlled process. This work demonstrates that the Pt/CNF composites synthesized by EPD are effective for ORR.  相似文献   

14.
Carbon nanotube (CNT)-supported platinum modified with HxMoO3 (Pt-HxMoO3/CNT) was prepared and used as an electrocatalyst for methanol oxidation. In the preparation of this electrocatalyst, a platinum precursor was loaded on CNTs and reduced by sodium borohydride in ethylene glycol, resulting in CNT-supported platinum without modification (Pt/CNT), and then the Pt/CNT was modified with HxMoO3 that was formed by hydrolysis and subsequent reduction of ammonium molybdate. The surface morphology, structure and composition of Pt-HxMoO3/CNT and Pt/CNT as well as their activity toward methanol oxidation were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), chronoamperometry (CA), chronopentiometry (CP), and electrochemical impedance spectroscopy (EIS). The results, obtained from TEM, XRD, EDS, and FTIR, indicate that the platinum loaded on CNTs has a face-centered cubic structure with particle sizes of 2–5 nm, and the modification of HxMoO3 on platinum with an atom ratio of Pt:Mo = 2:1 has little effect on the particle size, distribution and structure of the platinum. The results, obtained from CV, CA, CP, and EIS, show that the Pt-HxMoO3/CNT exhibits higher electrocatalytic activity toward methanol oxidation and better carbon monoxide tolerance than Pt/CNT.  相似文献   

15.
It is of great urgency to design inexpensive and high-performance oxygen reduction reaction (ORR) electrocatalysts derived from biowastes as substitutes for Pt-based materials in electrochemical energy-conversion devices. Here we propose a strategy to synthesize three-dimensional (3D) porous nitrogen-doped network carbons to catalyze the ORR from two-step pyrolysis engineering of biowaste scale combined with the use of a ZnCl2 activator and a FeCl2 promotor. Electrochemical tests show that the synthesized network carbons have exhibited comparable ORR catalytic activity with a half-wave potential (~0.85 V vs. RHE) and outstanding cyclical stability in comparison to the Pt/C catalyst. Beyond that, a high electron transfer number (~3.8) and a low peroxide yield (<7.6%) can be obtained, indicating a four-electron reaction pathway. The maximum power density is ~68 mW cm?2, but continuous discharge curves (at a constant potential of ~1.30 V) for 12 h are not obviously declined in Zn-air battery tests using synthesized network carbons as the cathodic catalyst. The formation of 3D porous structures with high BET surface area can effectively expose the surface catalytic sites and promote mass transportation to boost the ORR activity. This work may open a new idea to prepare porous carbon-based catalysts for some important reactions in new energy devices.  相似文献   

16.
Due to the poor performance and intermediates poisoning of available catalysts in direct methanol fuel cells (DMFC), the researcher is confronted with a considerable challenge for obtaining modified electrocatalyst. Ag–Ni porous coordination polymer (ANP) as a new electrocatalyst supporter was synthesized by a hydrothermal method. To achieve favorable electrocatalyst for DMFC systems, platinum nanoparticles was deposited upon ANP by an electrochemical method and platinum supported on Ag–Ni porous coordination polymer (Pt-ANP) was formed. Fourier transform infrared spectroscopy (FTIR) analysis ensured correct synthesized of ANP and Pt-ANP. In addition, the morphologies investigation of ANP and Pt-ANP were carried out by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The FE-SEM images indicate that the platinum nanoparticles have been greatly deposited on ANP surface. Electrochemical behaviors of prepared catalyst for methanol oxidation were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) techniques. Electrochemical cyclic voltammetry tests (CV) indicate that the forward peak current density of Pt-ANP is about 105 mA/cm2 which it is 33% more than the forward peak current density of pure Pt catalyst (70.21 mA/cm2). Moreover, electrochemical surface area (ECSA) of Pt-ANP is 26.42 m2/gPt. In addition, density functional theory (DFT) computations show that with the deposition of Pt upon ANP, the HOMO-LOMO energy gap of ANP has been decreased which they are suitable for electrochemical reactions. Theoretical results are greatly in accordance with the experiments. Based on the results, Pt-ANP could be a superior electrocatalyst for methanol oxidation.  相似文献   

17.
Transition metal-based compounds, due to their excellent ORR catalytic performance under alkaline condition, have recently emerged as one of the most promising alternatives to noble metal-based ORR catalysts. It is worth noting that manganese oxide can take an unique advantage for decomposition of intermediate adsorption products H2O2 and can effectively reduce O2 to OH. However, most research has focused on MnO2, while attention has rarely been paid to MnO catalysts. In addition, under high-temperature pyrolysis condition, MnO is the most stable manganese oxide but MnO nanoparticles easily agglomerate. Hence, it is very difficult to obtain well-dispersed and small-sized MnO nanoparticles. Herein, on the basis of pre-synthesizing uniformly distributed manganese complexes on the reduced graphene oxide (rGO), we innovatively prepare highly dispersed and small-sized MnO nanoparticles (~3.94 nm) via high-temperature pyrolysis, which are uniformly anchored on N-doped reduced graphene oxide (NrGO) as an efficient oxygen reduction electrocatalyst. The as-obtained MnO/NrGO (1050 °C) electrocatalyst achieves satisfactory onset potential (0.942 V) and half-wave potential (0.820 V) under alkaline condition. And the limiting current density is 4.17 mA cm−2, which is very close to that of Pt/C (20 wt%, JM). Meanwhile, MnO/NrGO (1050 °C) catalyst presents superior longstanding durability and methanol resistance than Pt/C (JM). This work indicates that high-temperature pyrolysis can improve the purity of manganese oxide, simultaneously the defects of NrGO can reduce particle size of MnO nanoparticles, which are greatly beneficial to improve ORR performance. This work provides a new idea for research of MnO catalysts for ORR in the future.  相似文献   

18.
Rational design of efficient, cost-effective electrocatalyst towards oxygen reduction reaction (ORR) is of vital importance to the wide application of polymer electrolyte membrane fuel cells. In this work, a novel and simple Na2SO4-assisted pyrolysis strategy with ZIF-12 as the precursor is reported for the synthesis of cobalt, sulfur, nitrogen, co-doped carbon (termed as CoSNC-xNa2SO4-T) materials towards ORR. Different from CoNC-800 derived from pure ZIF-12, with the presence of Na2SO4, the derived CoSNC-0.5Na2SO4-800 material exhibits layered flake morphology with hierarchical meso-microporous structure. Besides, CoSNC-0.5Na2SO4-800 material shows higher content of pyridinic-N and graphitic-N, higher relative intensity of Co-Nx, higher content of carbon defect, as well as larger specific surface area in comparison with CoNC-800, which results in higher activity of CoSNC-0.5Na2SO4-800. The CoSNC-0.5Na2SO4-800 material displays a half-wave potential of 0.88 V, which is superior to that of commercial Pt/C (half-wave potential being 0.86 V). Moreover, CoSNC-0.5Na2SO4-800 demonstrates a better durability compared with Pt/C. The pyrolysis temperature and the amount of Na2SO4 are found to affect the physiochemical properties and electrochemical performance of the CoSNC-xNa2SO4-T materials. This work not only provides a facile and novel synthesis approach for the preparation of highly active Co, S, N co-doped carbon materials for ORR, but also disclosing the key structure properties for enhancing the performance of these catalysts.  相似文献   

19.
Designing oxygen reduction reaction (ORR) catalysts with high activity and long durability is significant for the development of proton exchange membrane fuel cells. Herein, the optimized platinum nanowires are used as templates for inducing growth of cobalt-containing metal-organic framework, deriving uniform nanofibers. After the calcination, the metal ions are transferred into the nitrogen-rich porous carbon, and wrapped by the carbon skeleton to form the PtCo bimetal incorporated nanofibers as high-performance ORR electrocatalyst. The Pt4Co@NC-900 catalyst yields high specific activity (1.37 mA cm−2) in comparison to Pt/C (0.38 mA cm−2). The mass activity (MA) of Pt4Co@NC-900 catalyst is approximately 3.8-fold higher than that of the commercial Pt/C under acidic conditions. After the accelerated durability tests, the Pt4Co@NC-900 catalyst presents only 16% loss in MA, while Pt/C catalyst retains 73.0% of the initial MA. The improved ORR performance can be ascribed to the synergistic interaction between Co and Pt.  相似文献   

20.
We herein propose a dual ligand coordination strategy for deriving puissant non-noble metal electrocatalysts to substitute valuable platinum (Pt)-based materials toward oxygen reduction reaction (ORR), a key reaction in metal-air batteries and fuel cells. In brief, cobalt ions are firstly double-coordinated with proportionate 2-methylimidazole (2-MeIm) and benzimidazole (BIm) to obtain drum-like zeolitic imidazolate frameworks (D-ZIFs), which are then carbonized to output the final Co, N co-doped porous carbon (Co–N–PCD) catalyst inheriting the drum-like morphology of D-ZIFs. The Co–N–PCD is featured by mesopores and exhibits superb electrocatalytic behavior for ORR. Impressively, the half-wave potential of Co–N–PCD catalysts is 0.886 V with finer methanol-tolerance and stability than those of commercial Pt/C. Additionally, a zinc-air battery assembled from the Co–N–PCD displays an open-circuit voltage of 1.413 V, comparable to that of commercial Pt/C (1.455 V), suggesting the potentials of Co–N–PCD in practical energy conversion devices.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号