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1.
In view of the development of advanced bi-functional oxygen electrodes for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), herein, we report the synthesis of Co–Co3O4 nanostructure encased in N-doped carbon (Co–Co3O4/NC) by carbothermal reduction followed by controlled oxidative treatment. The formation of a protective-active oxide layer on the metallic-Co not only facilitated the effective charge separation and transport but also displayed improved stability of Co–Co3O4/NC in an alkaline operating condition. The Co–Co3O4/NC catalyst afforded 0.810 V overvoltage between ORR and OER in 0.1 M KOH solution, consequently, this lower reversible overvoltage would result in energy saving of around 0.246 V if Co–Co3O4/NC is used as an oxygen electrode instead of commercially available 40 wt % Pt/C. Furthermore, in comparison with the use of Pt/C + IrO2 as an ORR and OER catalyst, respectively the single bi-functional electrocatalyst i.e., Co–Co3O4/NC would result in energy saving of around 0.13 V.  相似文献   

2.
Developing high activities, stable, non-precious metal based bi-functional electrocatalysts oxygen evolution/reduction reactions (OER/ORR) in rechargeable metal-air batteries and regenerative fuel cell technologies is essential for future energy conversion and storage. In this work, the potential of utilizing the synthesized one-dimensional transition metal salen-type complexes (TM-SCs) as bi-functional electrocatalysts of ORR and OER is systematically explored by computational screening approach. The results demonstrate that different types of macrocyclic ligands, including N2O2, N3O and N4 as donor groups around the active sites, govern the OER/ORR catalytic performances. Co–SCs with N2O2 ligands exhibit the highest bifunctional catalytic activities. In particular, low limiting overpotentials of 0.22 V for OER and 0.33 V for ORR can be observed on Co sites, which are even superior to those of noble metal catalysts. Analyzing the linear relationships between the adsorption strength of intermediates and the overpotentials shows that the origin of excellent electrocatalytic performance is the smaller slope (0.86) for OOH1 vs OH1 on TM-SCs compared to metal surfaces, resulting in strengthened binding of the OOH1 intermediate. Besides, the adsorption energies of the intermediates bound on Co–N2O2 are close to the ideal values, while too strong on the Co–N3O and Co–N4 catalysts. By applying external strains, the adsorption strengths of reaction intermediates can be further modulated due to the tunable d-band centers, and the resulting ORR/OER activities are further boosted. Considering that the Co salen-based chain has been synthesized experimentally, this work highlights the excellent electrocatalytic performances of this new material and devises novel strategy by straining for catalyst optimizations.  相似文献   

3.
Exploring low-cost, efficacious and stable bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial yet highly challenging to the wide perspective practicability for rechargeable metal?air batteries together with fuel cells and electrochemical water splitting. Herein, we have successfully prepared a novel nanohybrid consisting of Co2P nanocores encased in N,P-codoped carbon layers (denoted as Co2P@NPC) through an extremely facile and effective pyrolysis route utilizing easily available raw materials. The as-prepared Co2P@NPC exhibits excellent bifunctional electrocatalytic performances for both ORR and OER in alkaline solution. For ORR, Co2P@NPC shows comparable activity to the commercial 20 wt% Pt/C in terms of the half-wave potential and limited current density under the identical linear sweep voltammetry measurement conditions. Moreover, the ORR durability and methanol tolerance of Co2P@NPC are much better than those of 20 wt% Pt/C. As regards OER, Co2P@NPC affords lower activity but better stability than the fresh RuO2. The high electrocatalytic performances originate from the strong interaction between Co2P nanocores and N,P-codoped carbon layers, the high BET surface area and the conductive network formed by the crosslinking of carbon coatings.  相似文献   

4.
Developing platinum-based nanoparticles on carbon catalysts with high activity and stability for oxygen reduction reaction (ORR) is of great significance for the practical application of fuel cells. Herein, a synchronous strategy of preparing nano-sized PtCo supported on atomic Co and N co-doped carbon nanorods (PtCo/Co–N–C NR) was developed to replace the conventional method of impregnating Pt sources into ready-made carbon materials, in which metal-organic frameworks (MOFs) with Co and Zn ions of rhombic dodecahedron were first prepared using 2-methylimidazole as building block and then their morphology was transformed into porous nanorods via the reduction of Co ions to Co–B–O complex in the MOFs by NaBH4; subsequently, Pt was deposited on the Co–Zn MOF nanorods through the displacement reaction of PtCl62- and metallic Co and coordination between MOF and PtCl62-; after pyrolysis and acid-leaching process, highly dispersed PtCo/Co–N–C NR was obtained. Attributed to its unique characteristics of hierarchical pore structure, uniform PtCo alloy nanoparticles with the average size of 7.0 nm and strong supporting interaction effect, the catalyst exhibits high ORR activity and stability with the mass activity of 577.0 mA mg?1Pt and specific activity of 1.4 mA cm?2 at 0.9 V vs RHE in 0.1 M HClO4, which is about 3.6 times and 3.5 times high than that of commercial Pt/C catalyst respectively. This strategy would provide a flexible route to develop highly active and stable ORR electrocatalysts with various morphologies for optimizing the exposure of active sites.  相似文献   

5.
The use of Pt-based cathode catalyst materials hinders the widespread application of anion exchange membrane fuel cells (AEMFCs). Herein, we present a non-precious metal catalyst (NPMC) material based on pyrolysed Fe and Co co-doped electrospun carbon nanofibres (CNFs). The prepared materials are studied as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts in alkaline and acidic environments. High activity towards the ORR in alkaline solution indicated the suitability of the prepared NPMCs for the application at the AEMFC cathode. In the AEMFC test, the membrane-electrode assembly bearing a cathode with the nanofibre-based catalyst prepared with the ionic liquid (IL) (Fe/Co/IL–CNF–800b) showed the maximum power density (Pmax) of 195 mW cm−2, which is 78% of the Pmax obtained with a commercial Pt/C cathode catalyst. Such high ORR electrocatalytic activity was attributed to the unique CNF structure, high micro-mesoporosity, different nature of nitrogen species and metal-Nx active centres.  相似文献   

6.
Design and development of cost-efficient multifunctional three-dimensional (3D) metal organic frameworks (MOFs) towards oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are very significant for green energy devices. Herein, a scalable one-pot solvothermal method is developed to obtain a series of multifunctional 3D flower-like MOFs. In addition, systematic studies are also conducted on the effects of various metal cations and N-containing ligands on the structures, compositions, and multifunctional performance of the obtained MOFs. As a result, 3D flower-like Co-MOFs using Co2+ as a metal cation and 2,2’:6′,2″-terpyridine as a N-containing ligand exhibit the highest multifunctional performance towards ORR, OER and HER. The scalable method provides a new prospect to design and develop other MOFs-based multifunctional catalysts.  相似文献   

7.
Bifunctional catalysts are vital for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in metal-air batteries. In this work, Co–Co3O4/N-doped carbon nanosheets (NCNs) were developed as highly efficient bifunctional oxygen catalysts via the pyrolysis of a hybrid ZIF-67/CNs precursor. It is found that the introduced CNs play important roles. On one hand, the introduced CNs can tune the surface contents of Co, N and/or O species that are closely correlated with OER and ORR activity. On the other hand, they also facilitate to achieve high specific surface areas for the catalysts. In addition, the introduced CNs helps the formed Co–Co3O4 hybrid nanoparticles with uniform and small sizes to be well-distributed on the NCNs substrates. Despite such important roles, it should be noted that a moderate content of the introduced CNs is required to achieve optimal oxygen catalytic activity. As a result, the optimized ZIF-67/CNs(1)-600 exhibits a low value of η10 (~350 mV) for OER and a high value of E1/2 (~0.85 V) for ORR. Its overall bifunctional activity (ΔE) is as low as ~0.73 V, which is comparable to the recent reported Co-based catalysts.  相似文献   

8.
In this work, a series of double perovskite oxide materials Pr1-xBa1+xCo2O6-δ (x = 0.05, 0.10, 0.15, and 0.20) was synthesized using the solid-state route method. Their catalytic activity and stability in 1 M KOH alkaline medium were investigated. The phase formation and structure of the prepared oxides were determined by Powder X-ray diffraction. The morphology of prepared catalysts was confirmed by SEM analysis. The catalytic performance of the prepared catalyst in alkaline solution was investigated using electrochemical measurements for both oxygen evolution reaction (OER) and oxygen reduction reactions (ORR). This series of double perovskite oxide materials exhibit catalytic activity for both OER and ORR. Pr0.90Ba1.10Co2O6-δ shows wonderful OER activity among all the catalysts with a specific capacitance of 598.40 F/g and double-layer capacitance of 38.94 mF/cm2. Power low gives a hint of oxide-ion intercalation pseudocapacitance in the Pr0.90Ba1·10Co2O6-δ. On the other hand, Pr0.95Ba1·10Co2O6-δ exhibits potential behavior for ORR. Overall, our findings highlight the combined effects of incorporating Ba into double perovskite PrBaCo2O6-δ in its behavior for OER and ORR.  相似文献   

9.
It is of great significance to develop efficient and inexpensive oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts for the current energy crisis. But this is still a long-term and formidable challenge. In this work, a two-phase synergistic effect between transition metal sulfides is applied in the design of ORR/OER bifunctional catalysts. Co-based zeolite imidazolate framework (MOF) is used as a precursor to prepare the hollow Co9S8 through vulcanization and heat treatment. At the same time, the phase transformation occurs to form some Zn0.76Co0.24S on surface during the heat treatment due to the Zn-polydopamine coating. The hollow structure Zn0.76Co0.24S–Co9S8 composite has been verified and promotes the diffusion of reactants and products, and the interaction between two phases greatly promotes the catalytic reactions. The coating of Zn-polydopamine forms uniform carbon layer on surface, enhancing the conductivity of Zn0.76Co0.24S–Co9S8 composite. The Zn0.76Co0.24S–Co9S8 composite shows much better performance of ORR and OER compared to any of them. The overpotential of OER at a current density of 10 mA/cm2 is 330 mV, and the half-wave potential of ORR is 0.83 V. Additionally, the Zn0.76Co0.24S–Co9S8 composite displays better cyclic stability. The synergistic effect of Zn0.76Co0.24S and Co9S8 can be considered as the foremost factor for the improvement of catalyst performance, which provides new possibilities for the development of non-precious metal bifunctional catalysts.  相似文献   

10.
Noble metal Pt is the acknowledged efficient catalyst for oxygen reduction (ORR) and hydrogen evolution reaction (HER) in commercial applications. However, due to its high price and limited reserves, its large-scale application is limited. In order to overcome this defect, the loaded Pt nanoparticles (NPs) should be small and dispersed efficiently through the design of electrode materials, so as to improve the utilization efficiency of Pt. In addition, the introduction of non-noble metal active sites can reduce the consumption of Pt efficiently. In this work, hollow graphene spheres are used as the carrier and the heteroatoms (N, Fe and Co) are introduced. The results show that the introduction of Fe and Co can form very effective heteroatom active sites (carbon encapsulated Fe/Co metals and FeCo alloy, and/or metal nitrides Fe/Co-Nx-C) in the substrate material, which improve the catalytic activity of the electrode material effectively and the utilization efficiency of Pt. In addition, the generation of Fe/Co-Nx-C active sites and the loading of Pt are also closely related to the doped N atoms. The onset potential, limiting current density (JL), half-wave potential (E1/2) and Tafel slope of sample FeCo-NxHGSs/Pt (10 wt%) can exceed or comparable to those of commercial catalysts Pt/C (20 wt%) towards ORR both in acid and alkaline electrolyte. Moreover, the values of η100 and the Tafel slope for FeCo-NxHGSs/Pt towards HER can also exceed the commercial catalysts Pt/C (20 wt%) in acid and alkaline electrolytes. The purpose of reducing the usage amount of precious metals without reducing the catalytic performance is realized. The relationship between the ORR and HER performance of the resultant electrode catalyst and the doped heteroatoms, such as nitrogen (N), iron (Fe) and cobalt (Co) atoms, was studied and discussed in detail.  相似文献   

11.
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   

12.
Non-precious metal-based electrocatalysts with excellent activity and stability are highly desired for the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a tannic acid (TA) etching strategy is used to inhibit the metal aggregation and achieve muti-metal doping. The hollow NH2-MIL-101@TA derived Fe–N–C catalyst exhibits superior ORR catalytic activity with an E1/2 of 0.872 V and a maximum output power density of 123.4 mW cm−2 in Zn-air battery. Since TA can easily chelate with metal ions, Fe/Co–N–C and Fe/Ni–N–C are also synthesized. Fe/Ni–N–C manifests exceptional bifunctional activity with an Ej = 10 of 1.67 V and a potential gap of 0.833 V between Ej = 10 and E1/2 in alkaline electrolyte, which is 45 mV smaller than Pt/C–IrO2. The improvement of ORR and OER performance of the catalysts via the simple TA etching and chelation method provides a novel strategy for the design and synthesis of efficient electrocatalysts.  相似文献   

13.
Achieving a highly active cathode surface with extremely efficient electrocatalysts for oxygen reduction kinetics is a fundamental necessity for durable fuel cells. Developing such active materials into desirable nanostructures is crucial in the pursuit of electrocatalysis. A facile preparation of cobalt decorated nitrogen and sulfur co-doped carbon nanostructures (Co–NSC) with the added advantage of Zeolitic imidazolate frameworks (ZIF), ZIF 67@ZIF 8 is reported here. The as-prepared Co, N, S, co-doped carbon (Co–NSC) electrocatalyst comes under platinum group metal-free (PGM-free) catalysts which intends to replace the scarce and highly expensive commercial Pt catalysts. Facile preparation of the Co–NSC catalyst that is scalable, low cost and highly ORR active makes the material advantageous. Co–doping sulfur has dramatically enhanced the intrinsic catalytic activity of the catalyst, and the degree of variation in sulfurization greatly influences the overall catalytic property. Co–NSC 200 with high sulfur doping exhibit a positively shifted onset potential of 0.81 V, and a high yielding current density of 5.5 mA cm?2 at 20 mV s?1.  相似文献   

14.
Highly active and durable Pt-based catalysts for oxygen reduction reaction (ORR) are very important and necessary for the proton exchange membrane fuel cells (PEMFCs). In this paper, we report the preparation and performance study of ORR catalysts composed of core-shell Pt–Co alloy nanoparticles (NPs) on multi-walled carbon nanotubes (MWCNTs) anchored with ZrO2 NPs (denoted as Pt–Co–ZrO2/MWCNTs). Thanks to the unique three-phase structure, the mass activity of Pt–Co–ZrO2/MWCNTs for ORR at 0.9 V versus reversible hydrogen electrode (RHE) is1577 mA mgPt?1, which is ~6.6-fold higher than that of the commercial Pt/C (238 mA mgPt?1). After 50,000 cycles for durability test, the mass activity of Pt–Co–ZrO2/MWCNTs for ORR remained 88% of its initial value. In stark contrast, that of Pt/C kept only about 56.3% of its initial value. More importantly, its catalytic performance was fully observed/verified in a H2-air PEMFC single cell test. When the Pt loading of Pt–Co–ZrO2/MWCNTs loaded cathode was one fourth of that with commercial Pt/C as the cathode catalyst, comparable cell performance was achieved. More impressively, the MEA with Pt–Co–ZrO2/MWCNTs underwent only 24.5% degradation in maximum power density after 30,000 accelerated durability tests (ADTs). However, the MEA with Pt/C after 30,000 ADTs exhibited 39.6% performance loss in maximum power density. The enhanced mass activity and catalytic durability of Pt–Co–ZrO2/MWCNTs could be attributed to the core-shell Pt–Co alloy NPs with Pt-rich surface and the interface effect between Pt–Co alloy NPs and oxygen vacancy-rich ZrO2 NPs. In addition, this research also provided a solution to the durability issue of cathodes without sacrificing ORR mass activity, which would promote practical application of PEMFCs.  相似文献   

15.
Metal and nitrogen co-doped catalysts have been promising alternatives to platinum group metal (PGM) catalysts for oxygen reduction reaction (ORR) over the past few decades. Herein, we have synthesized an efficient Fe–N–C catalyst by the co-calcination of NH2-MIL-101@PDA and melamine. The best Fe–N–C shows a positive half-wave potential of 0.844 V, which is 14 mV higher than that of Pt/C catalyst, as well as superior methanol resistance and long-term durability in alkaline electrolyte. In addition, Fe–N–C also exhibits pronounced catalytic activity and a direct 4e reaction pathway in acid electrolyte. We ascribed the excellent ORR performance of Fe–N–C to its crumpled structure, large specific surface area (584.6 m2 g−1) and high content of Fe-Nx sites (1.22 at. %). This study provides a simple way for the fabrication of excellent PGM-free ORR catalysts.  相似文献   

16.
Electrochemical reactions such as the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and methanol oxidation reaction (MOR) are essential for energy conversion applications such as water electrolysis and fuel cells. Furthermore, Pt or Ir-related materials have been extensively utilized as electrocatalysts for the OER, ORR, and MOR. To reduce the utilization of precious metals, innovative catalyst structures should be proposed. Herein, we report a bi-metallic phosphide (Ni2P and PdP2) structure surrounded by graphitic carbon (Ni–Pd–P/C) with an enhanced electrochemical activity as compared to conventional electrocatalysts. Despite the low Pd content of 3 at%, Ni–Pd–P/C exhibits a low overpotential of 330 mV at 10 mA cm?2 in the OER, high specific activity (2.82 mA cm?2 at 0.8 V) for the ORR, and a high current density of 1.101 A mg?1 for the MOR. The superior electrochemical performance of Ni–Pd–P/C may be attributed to the synergistic effect of the bi-metallic phosphide structure and core-shell structure formed by graphitic carbon.  相似文献   

17.
A simple method for synthesizing highly active electrocatalyst with bimetal Cu/Co and N co-doped porous carbon structures framework is reported in this study. The addition of Cu and Co elements improve the chemical and physical properties of the electrocatalyst, including abundant valid active sites, large specific surface area and good conductivity, which significantly boost electrocatalytic performances in oxygen reduction reaction (ORR). The onset and half-wave potentials of catalyst (Cu/Co/N–C#2) are 0.25 and 0.14 V (vs Ag/AgCl), respectively, which are positive than those of the 20% Pt/C catalysts. Moreover, the maximum output voltage and power density of the Cu/Co/N–C#2 catalyst-based air-cathode microbial fuel cells (MFCs) are enhanced to 677 mV and 1008 mW m−2, respectively, which are 1.25 and 1.31 times higher than those of the 20% Pt/C catalyst-based MFCs. This strategy using Cu-doped ZIF-67 as precursor to prepare bimetal- and nitrogen-codoped hollow carbon structures is a feasible method to boost ORR catalytic performance.  相似文献   

18.
The alkaline anion exchange membrane fuel cell (AEMFC) is one of the green solutions for the growing need for energy conversion technologies. For the first time, we propose a natural shungite based non-precious metal catalyst (NPMC) as an alternative cathode catalyst to Pt-based materials for AEMFCs application. The Co and Fe phthalocyanine (Pc)-modified shungite materials were prepared via pyrolysis and used for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) studies. The most promising ORR performance was observed in alkaline media for FePc-modified and acid-leached shungite-based NPMC material. The catalysts were also evaluated as cathode materials in a single cell AEMFC and peak power densities of 232 and 234 mW cm?2 at 60 °C using H2 and O2 gases at 100% RH were observed for CoPc- and FePc-modified acid-treated materials, respectively.  相似文献   

19.
Lithium transition metal oxide has superior performance for oxygen evolution reaction (OER), while its activity for catalyzing oxygen reduction reaction (ORR) is too low to meet the demand of practical applications. Herein, the NCM-based (NCM, LiNi1/3Co1/3Mn1/3O2) composite materials are prepared through the two steps method. The NCM-2 (Mn2O3/LiNi1/3Co1/3Mn1/3O2) hybrid material demonstrates excellent ORR catalytic property and high OER catalytic performance, as well as the superior stability. Besides, with NCM-2 hybrid materials as catalysts of air cathode, the Al-air battery and Zn-air battery both exhibit higher power density. Therefore, based on results of Brunauer-Emmett-Teller and O2 temperature programmed desorption analysis, the improved catalytic performance ascribed to large specific surface area, pore structure and enhanced oxygen adsorption ability. In this work, the catalytic activity of lithium transition metal oxide has been improved, and a new method was provided to synthesize bifunctional catalysts for metal-air batteries.  相似文献   

20.
Transition metal and nitrogen co-doped carbon catalysts for the oxygen reduction reaction (ORR) have emerged as promising candidates to replace the expensive platinum catalysts but still remain a great challenge. Herein, a novel and efficient nitrogen-doped carbon material with metal cobalt co-dopant (Co–N/C) has been prepared by pyrolyzing porphyrin-based covalent organic polymer where Co is anchored. The optimized 10%-Co-N/C catalyst through facilely and efficiently tuning the cobalt content is carefully characterized by XRD, Raman, XPS, SEM and TEM for composition and microstructure analysis. This catalyst with only 0.56% Co exhibits an excellent ORR catalytic activity with a positive half-wave potential of 0.816 V (vs. RHE) in 0.1 M KOH solution, which is comparable to that of commercial Pt/C (20 wt%). Notably, the 10%-Co-N/C catalyst displays better electrochemical stability with only a loss of 5.1% of its initial current density in chronoamperometric measurement and also gives rise to stronger methanol tolerance than Pt/C. The good ORR catalytic behaviour for this catalyst may be attributed to the dispersion of the Co-NX active sites via adjusting the contents of cobalt species in porous organic framework.  相似文献   

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