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1.
The high energy demand for electrochemical water splitting arises from sluggish oxygen evolution reaction (OER) kinetics. In this regard, Layered double hydroxide (LDH) has been introduced as an outstanding catalyst for the OER due to its exceptional physiochemical and 2D infrastructure properties. Herein, we report the design and synthesiss of core-shell nanostructured electrocatalyst by rationally decorating vertically oriented NiFe LDH ultrathin nanosheets on CuxO support (NiFe LDH@CuxO) via microwave-assisted hydrothermal reaction. For OER, the NiFe LDH@CuxO core-shell nanostructured catalyst demonstrated promising electrocatalytic performance, requiring only 1.43 V onset potential and 270 mV overpotential at 10 mA cm?2. The NiFe LDH@CuxO also outperformed pristine NiFe LDH and iridium oxide (IrO2) in terms of electrocatalytic activity, durability, and Faradaic efficiency. The fabricated NiFe-LDH@CuxO electrocatalyst with outer shell NiFe-LDH ultrathin nanosheets provides numerous exposed active sites, benefits electrolyte diffusion and oxygen gas releasing and also reduces the interfacial charge transfer resistance to enhance OER activity. Furthermore, exclusive core-shell 3D infra-structure effectively prevents NiFe-LDH nanosheets agglomeration and restacking, enhancing electrochemical stability.  相似文献   

2.
It is an inevitable choice to find efficient and economically-friendly electrocatalysts to reduce the high overpotential of oxygen evolution reaction (OER), which is the key to improve the energy conversion efficiency of water splitting. Herein, we synthesized Cu2S/Ni3S2 catalysts on nickel foam (NF) with different molar ratios of Ni/Cu by a simple two-step hydrothermal method. Cu2S/Ni3S2-0.5@NF (CS/NS-0.5@NF) effectively reduces the overpotential of OER, displaying small overpotentials (237 mV@100 mA cm?2 and 280 mV@500 mA cm?2) in an alkaline solution, along with a low Tafel slope of 44 mV dec?1. CS/NS-0.5@NF also presents an excellent durability at a relatively high current density of 100 mA cm?2 for 100 h. The excellent performance is benefited by the prominent structural advantages and desirable compositions. The nanosheet has a high electrochemical active surface area and the porous structure is conducive to electrolyte penetration and product release. This work provides an economically-friendly Cu-based sulfide catalyst for effective electrosynthesis of OER.  相似文献   

3.
In this study, montmorillonite (MMT) clay was modified with different acids to be used as support material. The modified MMT clay was used to obtain hydrogen in the hydrolysis reactions of NaBH4 (NaBH4-HR) as a support material for the Co–B and Co–Fe–B catalyst. During the activation of MMT clay, the effects of different acids, phosphoric acid (H3PO4) concentration, and impregnation time with H3PO4 were investigated. During the hydrogen generation from the NaBH4-HR, effects of Co loading, Fe loading, NaBH4 concentration, temperature and, catalyst durability were investigated. The maximum HGRs for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B treated with 5 M H3PO4 for 7 days were 1869 and 4536 mL/min/gcatalyst, respectively. The activation energies for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B catalyst samples were 49.5 and 38.90 kJ/mol.  相似文献   

4.
Seawater electrolysis has become an efficient method which makes full use of natural resources to produce hydrogen. However, it suffers high energy cost and chloride corrosion. Herein, we first present a Ni2P/Co(PO3)2/NF heterostructure in which Co(PO3)2 with the nano-rose morphology in-situ grown on the rough Ni2P/NF. The unique 3D nano-rose structure and the optimized electronic structure of the heterostructure enable Ni2P/Co(PO3)2/NF super-hydrophilic and super-aerophobic characteristics, and highly facilitate hydrogen evolution reaction (HER) kinetics in alkaline fresh water, alkaline seawater and even industrial wastewater at large current density, which is rarely reported. Significantly, at large current densities, Ni2P/Co(PO3)2/NF only requires overpotentials of 217 and 307 mV for HER to achieve 1000 mA cm−2 in alkaline fresh water and alkaline seawater, respectively, and requires an overpotential of 469 mV for HER to deliver 500 mA cm−2 in industrial wastewater. Furthermore, the overall seawater splitting system in the two-electrode electrolyzer only requires voltage of 1.98 V to drive 1000 mA cm−2, which also demonstrates significant durability to keep 600 mA cm−2 for at least 60 h. This study opens a new avenue of designing high efficiency electrocatalysts for hydrogen production at large current densities in alkaline seawater and industrial wastewater.  相似文献   

5.
The development of non-precious metal catalysts for the electrochemical oxygen evolution reaction (OER) is especially important for the water electrolysis process. Herein, a two-dimensional (2D) ultrathin hybrid Co–NiFe layered double hydroxide (LDH) is synthesized via a facile hydrothermal method. In 1.0 M KOH electrolyte, Co–NiFe LDH exhibits remarkable activities for OER. At the current density of 10 mA cm−2, it only needs an overpotential of 278 mV, which is ca. 50 mV and 20 mV lower than those for NiFe LDH (328 mV) and RuO2 catalysts (298 mV), respectively. In addition, Co–NiFe LDH also shows impressive long-term stability for OER. Besides the stable morphology and crystal structure, the potential is always kept at 1.50 V and shows almost no attenuation during the 20 h of durability test. Changes in the electronic structure of LDH due to introduction of Co ions, as well as the large specific surface area facilitate the mass/electron transfer and the oxygen bubbles release, and thus lead to the enhanced catalytic properties for OER. This work can be informative not only for understanding the role of physical and electronic structures on OER but also for designing high-performance non-precious metal OER electrocatalysts.  相似文献   

6.
The slow four-electron transfer of the oxygen evolution reaction (OER) greatly limits the water splitting efficiency, so the development of high-efficiency and stable OER electrocatalysts is of great significance for large-scale alkaline water splitting. Herein, we reported an efficient self-supported OER electrocatalyst of Ag NPs decorated ultrathin Co(OH)2 nanosheets supported on nitrogen-doped carbon (NC) nanoflake arrays on carbon cloth (Ag/Co(OH)2@NC/CC). Our designed 3D unique electrode structure with heterointerfaces and hierarchical nanosheets endow Ag/Co(OH)2@NC/CC with outstanding OER electrocatalytic activity (300 and 350 mV at 50 and 100 mA/cm2, 79.8 mV/dec of Tafel slope) and good long-term durability in 1 M KOH. Furthermore, the related results of electrochemical tests show that the improved conductivity, increased electrochemical active sites and enhanced intrinsic active sites explain the superior OER performance. Our study will offer some new ideas in constructing new highly-active materials for various other energy conversion fields.  相似文献   

7.
To exploit the low-cost and efficient catalyst for the hydrolytic dehydrogenation of ammonia borane, trace amount of palladium-doped transition metal (Cu, Ni, Co, Fe and Zn) nanoparticles have been incorporated into the interior of metal-organic frameworks named ZIF-8, ZIF-67, ZIF-67/ZIF-8 and core-shell ZIF-67@ZIF-8 by a double-solvent approach. The optimized catalyst of CuPd0.01@ZIF-67@ZIF-8 composite exhibited an excellent activity with a turnover frequency (TOF) value of 30.15 mol H2 (molmetal)−1 min−1 at 298 K and a relatively low activation energy of 38.78 kJ mol−1. It might attributed to both ultrafine size of metal nanoparticles (~3 nm) induced by the confinement of core-shell ZIF-67@ZIF-8 and the synergistic effect between Pd and Cu. Moreover, the detailed kinetic study has manifested that this catalytic reaction is first-order in regards to the catalyst amount while zero-order as for the concentration of ammonia borane. In addition, the durability and recyclability of CuPd0.01@ZIF-67@ZIF-8 have been demonstrated to be great.  相似文献   

8.
Herein, CoO and CoMoO4 heterostructure supported on nickel foam (CoO/CoMoO4@NF) are proposed as an effective bifunctional hydrogen evolution reaction (HER) and hydroxide reaction (HOR) electrocatalyst. The electron density distribution at the interface can be optimized by coupling CoO and CoMoO4, thereby improving conductivity and regulating the hydrogen binding energy (HBE) and hydroxyl binding energy (OHBE). CoO/CoMoO4@NF exhibits high stability and activity with an exchange current density of ∼3.67 mA cm−2. Co/CoMoO4@NF reaches the current density of −10 mA cm−2 at only −29 mV and the corresponding Tafel slope of 40.2 mV dec−1. This work provides a promising solution for non-precious metal catalyst for hydrogen reaction in energy storage.  相似文献   

9.
The oxygen evolution reaction (OER) plays a vital role in various energy conversion applications. Up to now, the highly efficient OER catalysts are mostly based on noble metals, such as Ir- and Ru-based catalysts. Thus, it is extremely urgent to explore the non-precious electrocatalysts with great OER performance. Herein, a simple electrodeposition combined with hydrothermal method is applied to synthesize a non-precious OER catalyst with a three-dimensional (3D) core-shell like structure and excellent OER performance. In our work, NiFe layered double hydroxide (LDH) was electrodeposited on Ni3S2 nanosheets on nickel foam (NF), which exhibits a better performance compared with RuO2, and a low overpotential of 200 mV is needed to reach the current density of 10 mA/cm2 in 1 M KOH. Notably, the Ni3S2/NiFe LDH only need an overpotential of 273 mV to reach the current density of 200 mA/cm2.  相似文献   

10.
Aiming at fabricating high-activity and stable methane combustion catalysts in the dry/wet conditions, Co–Mn binary oxides were employed as promoters to Pd/Al2O3 system herein. The introduction of appropriate amount of manganese made Mn3+ maximally enter into the Co3O4 spinel structure, conducive to the conversion of Co3+ to Co2+ by Mn3+ and then the enhancement of lattice distortion. Therefore, abundant oxygen vacancies were produced, which enhanced the surface-concentrations of active Pd2+ and Oads species, together with the exchange of oxygen species. The resulting catalyst with a molar Mn/Co ratio of 0.20 performed superior low-temperature activity and durability. Moreover, the synergy of Mn and Co could accelerate the removal process of accumulated OH/H2O from the active sites, thereby promoting the regeneration of PdO and oxygen vacancies. This endowed the tailored catalyst with remarkable moisture-tolerance and hydrothermal stability, and inspiring enhanced activity (T90 = 350 °C) after removing water vapor.  相似文献   

11.
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   

12.
Ni-based monometallic and bimetallic catalysts (Ni, NiRh, NiCo and NiFe) supported on Ce0.5Zr0.5O2 support were evaluated on the steam reforming of ethanol (SRE) performance. The supports of Ce0.5Zr0.5O2 composite oxide was prepared by co-precipitation method with Na2CO3 precipitant and assigned as CeZr(N). The monometallic catalyst was prepared by incipient wetness impregnation method and assigned as Ni/CeZr(N). The bimetallic catalysts were prepared by co-impregnation method to disperse the metals on the CeZr(N) support and assigned as NiM/CeZr(N). All samples were characterized by using XRD, TPR, BET, EA and TEM techniques at various stages of the catalyst. The results indicated that the facile reduction and smaller particle size of Ni/CeZr(N) (T99 = 300 °C) and NiRh/CeZr(N) (T99 = 250 °C) catalysts were preferential than the NiFe/CeZr(N) (T99 = 325 °C) and NiCo/CeZr(N) (T99 = 375 °C) catalysts. Also, both the Ni/CeZr(N) and NiRh/CeZr(N) catalysts displayed better durability among these catalysts over 100 h and 400 h, respectively. Since the serious coke formation for the NiCo/CeZr(N) catalyst, the activity only maintained around 6 h, the durability on the NiFe/CeZr(N) catalyst approached 50 h.  相似文献   

13.
Developing highly efficient bifunctional urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) catalysts for urea splitting to hydrogen are one of the strategies to cope with the energy crisis. Here, a series of CrxPy-a/ComPn-b composites were synthesized on Ni foam through hydrothermal and low-temperature phosphorization process for the first time. It is worth noting that CrxPy-1/ComPn-3@NF exhibited excellent UOR performance (1.331 V at 100 mA cm?2) and HER performance (0.299 V at 100 mA cm?2) in an electrolyte of 1 M KOH and 0.5 M urea due to the synergistic effect of Cr–Co. The CrxPy-1/ComPn-3@NF||CrxPy-1/ComPn-3@NF two-electrode system call for only 1.52 V to provide current density of 10 mA cm?2, which is one of the best electrochemistry performances reported up to now. Experimental analysis show that the promoted electrochemistry performances is assigned to faster charge transfer rate, the exposure of more reaction site and better properties of metals. Density Functional theory (DFT) results demonstrate that the presence of the ComPn material accelerates the kinetics of hydrogen production and the CrxPy material improves the properties of metals for the electrode. The work provides a new idea to develop the environmentally friendly and low cost overall urea splitting catalyst with transition metals instead of noble metals.  相似文献   

14.
In the present work, a core-shell structured Co/SiO2@HZSM-5 catalyst was prepared for hydrogen production from syngas of plastic waste gasification. The cobalt catalyst was coated with HZSM-5 shell through a hydrothermal process, and the Co/SiO2@HZSM-5, with different loadings of HZSM-5 (e.g., 10–30 wt %) exhibited excellent activity and durability for dehydrogenation reactions. The amount of HZSM-5 was found to be an important factor for hydrogen production. Temperature-programmed reduction with H2 and temperature-programmed desorption of ammonia was applied to determine the active site and the acidity of prepared catalyst, respectively. The prepared Co/SiO2@HZSM-5 was tested through reforming of plastic gasification syngas and shown superior hydrogen production ability (∼90%) and stability (over 15 h). The effects of reduction-oxidation behavior on the catalytic performance were also discussed.  相似文献   

15.
Achieving high catalytic performance with the lowest possible amount of noble metal is critical for any catalytic applications. Herein, we report a controllable method of preparing low Ru loaded, N-doped porous carbon embedded with cobalt oxide species (Ru/CoOx@NPC) using core-shell metal-organic framework (MOF) as a template. The optimized catalyst exhibits a highly powerful yet stable performance of H2 production through sodium borohydride (NaBH4) hydrolysis. The Ru/CoOx@NPC catalyst shows a fast H2 generation rate (8019.5 mL min?1 gcat?1), high turnover frequency (1118.6 mol min?1 molRu?1), and reusability. The carbonized ZIF-8 core and the ZIF-67 outer shell supplies a porous carbon moiety that not only improves the conductivity and but also provides uniform distribution of the active sites. The XPS analysis indicates that there is a strong electronic interaction between Co species and Ru species. The superior catalytic performance can be attributable to the large specific surface area as well as the synergy between Co-oxide and Ru clusters.  相似文献   

16.
Rational design and construct heterointerfaces of noble-metal-free materals is of very important to prepare high-performance electrocatalysts for hydrogen evolution reactions (HER). Herein, a novel 3D core-shell NiS@CoS@CC with abundant heterointerfaces is synthesized via a three-step strategy. The three-steps involve the rectangular Co(OH)2 nanosheet arrays were grown on the CC, Ni(OH)2 nanowires further grown on the Co(OH)2 nanosheets to form a novel core-shell architecture (that is, nanosheets wrapped with nanowires), and the conversion of hydroxides to sulfides. In the 3D NiS@CoS@CC heterostructure, NiS are dispersively distributed on the surface of rectangular CoS nanosheets to form abundant heterointerface active sites, meanwhile, a large number of tiny pores are uniformly distributed over the core-shell structure due to the conversion of hydroxides to sulfides. The abundant NiS@CoS core-shell heterointerfaces can decrease the free energy of adsorption of Hads and enhance electronic conductivity through electronic coupling effects between different components, facilitate the electron transfer from the CoS nanosheets to the surrounding NiS. Furthermore, 3D porous structure can provide abundant edge sites and more electroactive surface area, and can accelerate the diffusion of gaseous products. Consequently, the as-prepared NiS@CoS@CC electrocatalyst presents remarkably enhanced performance for the HER in alkaline medium. The overpotential for HER is as low as 30 mV at a current density of 10 mA cm−2. Correspondingly, the Tafel slope of the electrode reaction is 97 mV dec−1. Particularly, the catalyst maintained a high stability (the final polarization curves suffer negligible degradation in comparison with the initial after taking 1000 continuous CV). The work provides a viable technical solution for fabricating heterostructure materials with excellent performances for future energy storage and conversion devices.  相似文献   

17.
As a promising class of alternatives to noble metal-based oxygen electrocatalysts, hybrids of metal/metal oxide (M/MO) and N-doped carbon have been widely explored. To address the often-insufficient catalytic activity of single M/MO-embedded N–C systems, researchers have introduced a second M/MO, usually via wet processes. In this work, we leverage the unique capability of atomic layer deposition (ALD) to enable the introduction of a trace amount of ceria throughout a Co/CoOx-embedded N-doped carbon nanostructure in a highly uniform and dispersed manner to maximize heterogeneous interfacial areas and thus catalytically active sites. An optimally prepared catalyst achieves an ORR onset potential of 0.95 V (0.1 M KOH) and an OER potential of 1.53 V at 10 mA cm−2 (1 M KOH) and exhibits excellent cyclic durability. Quasi-operando observations reveal the multifaceted roles of the tiny amount of introduced ceria in facilitating electrocatalytic activity and enhancing durability. The ceria activates reactant adsorbates and transfers the activated intermediates to neighboring CoOx and electronically couples with Co and N species for enhanced catalytic activity. A high concentration of trivalent Ce state is readily and continuously restored during ORR/OER for an uninterrupted activation of reactants, also contributing to a highly stable reaction.  相似文献   

18.
Development of robust and cheap catalyst for fast hydrogen evolution from ammonia borane (AB) aqueous solution is an interesting and important topic in the field of hydrogen energy. Herein, a novel non-precious Co3xCu3-3x(PO4)2 catalyst possessing high reactivity in AB hydrolysis has been developed for the first time. By tuning the molar ratio of Co and Cu, a series of Co3xCu3-3x(PO4)2 with different x were synthesized and the catalytic behavior in AB hydrolysis was examined. At the optimal x of 0.8, an ultrahigh turnover frequency of 72.6 min−1 was achieved. Additionally, the synergistic effect between Cu3(PO4)2 and Co3(PO4)2 was experimentally confirmed, and the reaction kinetics of AB hydrolysis catalyzed by Co2.4Cu0.6(PO4)2 were investigated. This work provides a simple route and some new insights for the fabrication of a cheap P-containing catalyst with robust catalytic performance.  相似文献   

19.
Developing greatly efficient and steady non-noble metal bifunctional electrocatalyst is of great significance for reducing the energy consumption. In this work, we found that the construction of hierarchical nanostructures was an effective strategy to improve the catalytic performance of bimetallic transition-metal phosphide (NiCoP). Herein, we successfully synthesized the Ni1.5Co1.5P catalyst with porous nanosheet self-assembled microflowers (MFs) structure by sequential solvothermal, annealing and phosphorization treatment, and then adjusted the morphology of the MFs by changing the Ni/Co molar ratio to optimize its electronic structure and increase the exposed active sites, thereby improving catalytic activity of the catalyst. Specifically, the Ni1.5Co1.5P/MFs only required overpotentials of 141 mV and 314 mV to reach a current density of 10 mA cm−2 toward HER and OER, respectively. Impressively, during the continuous 12 h chronoamperometry measurement, the Ni1.5Co1.5P/MFs displayed good durability. In conclusion, this study provided a feasible strategy to explore and prepare low-cost non-noble metal bifunctional electrocatalysts.  相似文献   

20.
Developing highly efficient and low cost electrocatalysts for hydrogen evolution reaction (HER) is a popular topic for electrocatalytic water splitting to hydrogen technology. Herein, we report a novel heterostructure electrocatalyst prepared by the S-doping multilayer niobium carbide (S-ML-Nb4C3Tx) through hydrothermal technique. Compared with pristine ML-Nb4C3Tx catalyst, the as prepared electrocatalyst presents remarkable catalytic activity for HER with lower overpotential of 118 mV@10 mA/cm2 and a Tafel slope of 104 mV dec?1 in 1.0 M KOH solution. In addition, the catalyst exhibits a stable electrochemical durability of as long as 24 h in 1.0 M KOH. Efficient HER ability of the S-ML-Nb4C3Tx catalyst is mainly attributed to the following points: Firstly, the ML-Nb4C3Tx with superior conductivity and stability can effectively avoid the aggregation and oxidation. Secondly, the conversion of fluorine termination groups to –OH by TMAOH treatment can expose more active sites. Further, after the S-doping by hydrothermal reaction, NbS2 nanoparticles can prevent the ML-Nb4C3Tx nanosheets from restacking. As a result, the enlarged interlayer spacing and porous structure of the catalyst are conducive to the charge transfer. In addition, the introduction of NbS2 nanoparticles on the surface of ML-Nb4C3Tx can form heterostructure and subsequently adjust the electronic structure of the catalyst, accelerate the electron transfer, and improve the HER performance. This work presents a new strategy for the designing and preparation of low cost MXene-based catalysts for HER application.  相似文献   

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