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1.
Hydrogen production through water splitting is an efficient and green technology for fulfilling future energy demands. Carbon nanotubes (CNT) supported Ni2P has been synthesized through a simpler hydrothermal method. Ni2P/CNT has been employed as efficient electrocatalysts for hydrogen and oxygen evolution reactions in acidic and alkaline media respectively. The electrocatalyst has exhibited low overpotential of 137 and 360 mV for hydrogen and oxygen evolution reactions respectively at 10 mA cm?2. Lower Tafel slopes, improved electrochemical active surface area, enhanced stability have also been observed. Advantages of carbon support in terms of activity and stability have been described by comparing with unsupported electrocatalyst.  相似文献   

2.
Transition metal selenides are regarded as promising materials for the production of clean energy through electrocatalytic water splitting. Creation of defects in these metal selenides is one of the prudent strategies to enrich the active sites which in turn enhances the electrocatalytic activity of these materials and makes them viable for broader applications. Herein, defect-induced, iron-doped nickel selenide nanoparticles were prepared for the first time and their electrocatalytic efficacy towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been demonstrated. FexNi1-xSe2 nanoparticles (x = 0.25, 0.50, 0.75) were prepared using a facile hydrothermal method, in which defects were induced by annealing at 300 °C to obtain DI-FexNi1-xSe2. The structural and morphological investigations confirmed the size reduction and creation of defects after annealing, without any significant change in the crystal structure, which in turn is expected to promote the electrocatalytic activity. Accordingly, among all the materials investigated, DI-Fe0.25Ni0.75Se2 has shown the highest HER activity in 0.5 M H2SO4 at a lesser overpotential of 128 mV at 10 mA cm?2 and the Tafel slope was calculated to be 37.9 mV dec?1. Interestingly, the same material has displayed high performance towards OER in 1 M KOH with a lesser overpotential at 205 mV and a Tafel slope of 55.5 mV dec?1. Thus obtained electrocatalytic activity was much better than the reported nickel selenide based electrocatalysts. Further, the DI-Fe0.25Ni0.75Se2 electrocatalyst has demonstrated impressive stability in the acidic and alkaline medium during continuous electrolysis even up to 12 h.  相似文献   

3.
Novel binary metal Fe0.5Co0.5Se2 spheres supported on carbon fiber cloth (CFC) as efficient electrocatalyst for oxygen evolution reaction (OER) have been successfully synthesized by a facile solvothermal selenization using N, N-dimethylformamide (DMF) as solvent. Firstly, Fe0.5Co0.5 nanosheets have been electrodeposited on the surface of CFC. Then, Fe0.5Co0.5/CFC as precursor has been converted to uniform Fe0.5Co0.5Se2 spheres on CFC (Fe0.5Co0.5Se2/CFC) by DMF selenization process. XRD and EDX confirm the typical crystalline structure and homogeneous elemental distribution of Fe0.5Co0.5Se2 on the surface of CFC. XPS shows the existence and valence of Fe, Co and Se. The uniform size and good dispersion of Fe0.5Co0.5Se2 spheres with the diameter of about 100 nm have been revealed by SEM and elemental mapping, which may provide more active sites for OER. The electrochemical results demonstrate that the obtained Fe0.5Co0.5Se2/CFC possesses the better OER activity with smaller overpotential, lower Tafel slope and charge transfer resistance than other samples, which may be ascribed to the uniform spherical morphology and the better intrinsic activity from binary metal Fe0.5Co0.5Se2. Moreover, the faster electron transfer rate derived from CFC support and the synergistic effect between Fe0.5Co0.5Se2 and CFC may be responsible for the enhancements of OER performances.  相似文献   

4.
Integrating transition metal complexes with carbon-based materials, especially graphene, is a useful strategy for synthesizing effective hydrogen evolution catalysts. Herein, we report a design of hollow hexagonal NiSe–Ni3Se2 nanosheets grown on reduced graphene oxide (NiSe–Ni3Se2/rGO) by a simple hydrothermal method as an effective catalyst for hydrogen evolution reaction (HER) in the full pH range. In 0.5 M H2SO4, the NiSe–Ni3Se2/rGO possesses 112 mV to achieve 10 mA cm?2 and a small Tafel slope (61 mV dec?1). In 1.0 M PBS and 1.0 M KOH, the overpotentials are 261 and 188 mV at 10 mA cm?2, and Tafel slopes are 103 and 92 mV dec?1, respectively. Meanwhile, it owns good cycle stability and durability over 20 h in the whole pH range (0-14). In all solutions, the HER performance of NiSe–Ni3Se2/rGO is better than that of NiSe–Ni3Se2. This is because the rGO substrate accelerates the electron transfer and improves the electrical conductivity, increasing HER activity of catalyst.  相似文献   

5.
The development of efficient, cost-effective routes to prepare non-platinum-based electrocatalysts is a significant scientific challenge in water-splitting systems. A multifunctional electrocatalyst for the hydrogen evolution, oxygen evolution, and oxygen reduction reactions (HER/OER/ORR) involved in the water-splitting process was fabricated using a simple and eco-friendly strategy. The present study involves the simple synthesis of nanostructured nickel selenide (NiSe) via a hydrothermal method. The different phases of nickel selenide and their dependency on the precursor concentration were analyzed using X-ray diffraction (XRD). The morphologies of coral-like structured pure and Mo-doped NiSe (Ni1-xMoxSe) samples were investigated systematically using scanning electron microscopy (SEM). The as-prepared Ni0.5Mo0.5Se material showed an enhanced electrochemical activity of 1.57 V @ 10 mA/cm2 for OER and 0.19 V @ 10 mA/cm2 to HER, and follows the Volmer-Heyrovsky for HER mechanism. In addition, the electrocatalyst exhibits a large electrochemical surface area and high stability. Therefore, the hydrothermally synthesized Ni1–xMoxSe has been proven to be a perfect platinum-free trifunctional electrocatalyst for water splitting process.  相似文献   

6.
Binder-free NiFe-based electrocatalyst with aligned pore channels has been prepared by freeze casting and served as a bifunctional catalytic electrode for oxygen and hydrogen evolution reaction (OER and HER). The synergistic effects between Ni and Fe result in the high electrocatalytic performance of porous NiFe electrodes. In 1.0 M KOH, porous Ni7Fe3 attains 100 mA cm−2 at an overpotential of 388 mV with a Tafel slope of 35.8 mV dec−1 for OER, and porous Ni9Fe1 exhibits a low overpotential of 347 mV at 100 mA cm−2 with a Tafel slope of 121.0 mV dec−1 for HER. The Ni9Fe1//Ni9Fe1 requires a low cell voltage of 1.69 V to deliver 10 mA cm−2 current density for overall water splitting. The excellent durability at a high current density of porous NiFe electrodes has been confirmed during OER, HER and overall water splitting. The fine electrocatalytic performances of the porous NiFe-based electrodes owing to the three-dimensionally well-connected scaffolds, aligned pore channels, and bimetallic synergy, offering excellent charge/ion transfer efficiency and sizeable active surface area. Freeze casting can be applied to design and synthesize various three-dimensionally porous non-precious metal-based electrocatalysts with controllable multiphase for energy conversion and storage.  相似文献   

7.
Water electrolysis for producing hydrogen is considered to be the most feasible means to develop new green energy. Compared with above, urea electrolysis can improve energy conversion efficiency by introducing urea, and can also be used for purification of wastewater rich in urea. In this paper, a bifunctional electrocatalyst with heterostructure, namely Fe7Se8@Fe2O3 nanosheets supported on nickel foam, were synthesized for the first time through typical hydrothermal and partial oxidation processes. Iron cation promotes electron transfer and adjusts electron structure under the synergistic action of selenium and oxygen anion, thus achieving excellent catalytic activity of urea electrolysis. In an alkaline solution of 1 M KOH with 0.5 M urea, the Fe7Se8@Fe2O3/NF catalyst can drive the current density of 10 mA cm?2 with requiring only potential of 1.313 V and overpotential of 141 mV for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER), respectively. What is noteworthy is that Fe7Se8@Fe2O3/NF heterostructure is used as bifunctional electrocatalyst to form urea electrolyzer device, which only needs potential of 1.55 V to drive current density of 10 mA cm?2, which is one of the best catalytic activities reported so far, and the electrode couple showed remarkable stability for 15 h. Density functional theory shows that the Fe7Se8@Fe2O3/NF material exhibits the minimum Gibbs free energy for the adsorption of hydrogen. This work provides a new method for exploring novel and environmentally friendly bifunctional electrocatalysts for urea electrolysis.  相似文献   

8.
Bimetallic Ni–Fe phosphide electrocatalysts were in-situ synthesized through direct phosphorization of metal salts on carbon cloth (CC). The Fe dopant remarkably enhances the OER performance of Ni2P in alkaline medium through the electronic structure modulation of Ni. The (Fe0.5Ni0.5)2P/CC electrode, composed of uniform films coated on carbon fibers, delivers a low overpotential of 260 mV with a small Tafel slope of 45 mV·dec−1 at the current density of 100 mA cm−2, outperforming most reported non-noble electrocatalysts and commercial RuO2 electrocatalyst. The (Fe0.5Ni0.5)2P/CC also displays superior electrochemical stability at high current density. An appropriate Fe dopant level facilitates the in-situ transformation of Ni–Fe phosphides into active NiFeOOH during alkaline OER. This work simplifies the synthesis procedure of metal phosphides.  相似文献   

9.
Water electrolysis for green hydrogen production is gaining tremendous attention in the quest towards sustainable energy sources. At the heart of water splitting technology are the electrocatalysts, which facilitate the two half-cell reactions, i.e., the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with the latter being the most thermodynamically uphill. Herein, we managed to fabricate Ni1-xFexO microflowers (μFs) with varying % of Fe doping (0 < x < 0.36) via an easy chemical bath deposition (CBD) method. The as-synthesized μFs drop-casted on graphene paper (GP) are then applied as electrocatalysts for OER. Compared to contrast catalysts, the electrocatalyst with xFe = 0.1 exhibits a lower overpotential of 297 mV at a current density of 10 mA cm−2, Tafel slope of 44 mV dec−1 and unprecedented turnover frequency of 4.6 s−1 at 300 mV. It is believed that this remarkable electrochemical performance mainly stems from the synergistic effects of Ni and Fe species, working in harmony to enhance charge transfer kinetics and intrinsic activity of the catalyst. This work provides a promising avenue for developing cost-effective and highly active electrocatalysts as advanced electrodes for energy related applications.  相似文献   

10.
A cost-effective, efficient and stable electrocatalyst is a remarkable and significant prospect for hydrogen evolution reaction. By adjusting the copper contents, the Hexagonal and Tetragonal phases of the copper selenide have been synthesized using the solvo-hydrothermal process. Hexagonal phased-based copper selenide has exhibited a greater current density than the Tetragonal phase. However, the augmented structure, lower Gibbs Free energy, greater electrical conductivity and electrochemical surface promoted the electrocatalytic behavior of Hexa-CuSe-1.04 nanosheets. Hexa-CuSe-1.04 nanosheets exhibit a good overpotential of 61 mV at the state of art current density of 10 mAcm−2 along with Tafel slope of 59 mV dec−1 in 1 M KOH, which is better than the other Hexagonal phase structure, Hexa-CuSe-1.67 nanosheets and Tetra-Cu2Se-1.30 phase of the copper selenides. The electrocatalyst Hexa-CuSe-1.04 maintains the current density for a long duration and exhibits a similar linear sweep voltammetry curve in 1 M KOH during the chronoamperometry test. Moreover, Hexa-CuSe-1.04 nanosheets show a good Tafel slope of 26 mV dec−1 with a good turnover frequency of 72.40 m s−1 in 0.5 M H2SO4 and follow the Tafel phenomenon. Optimized density functional theory reveals that Hexa-CuSe-1.04 exhibits the lower Gibbs of 1.04 eV, free energy, which promotes the desorption and recombination process of the active hydrogen atoms at the active sites and enhanced the hydrogen evolution process. All results indicate the leading potential application of the Hexagonal phase of Hexa-CuSe-1.04 for hydrogen evolution reaction.  相似文献   

11.
Herein, based on the mechanical alloying (MA) and in situ electrochemical etching methods, a series of porous Ni–Fe electrocatalysts with different Ni/Fe atomic ratios derived from intermetallic NiFe aluminides have been designed and applied to OER (oxygen evolution reaction) in alkaline solution. As comparing with bulk NiFe aluminides electrocatalyst, the porous electrocatalyst presents higher activity via the etching method. In addition, among all porous samples with different metal stoichiometric ratios, Ni2/3Fe1/3Al shows the highest OER activity with an overpotential of 299 mV at 10 mA cm?2 and a Tafel slope of 58.9 mV dec?1, which can be attributed to the high intrinsic activity and large electrochemical surface area from the leaching of Al. This work provides a promising route to in situ synthesize highly efficient electrocatalysts for water splitting.  相似文献   

12.
Slow kinetics and insufficient understanding of the perceptual design of oxygen evolution reaction (OER) electrocatalysts are major obstacles. Overcoming these challenges, heterostructures have recently attracted attention because they encourage alternative OER electrocatalysts with active structural features. In this study, synthesis, characterization and electrochemical evaluation of the heterostructure of iron oxide/iron sulfide (Fe2O3/FeS) and its counterparts, iron oxide (Fe2O3) and iron sulfide (FeS) are reported. The structural features of as-synthesized electrocatalysts have been evaluated by infrared spectroscopy, powder X-ray diffraction study and scanning electron microscopy. Fe2O3/FeS was found to be a stable electrocatalyst for efficient water splitting, which initiates OER at a surprisingly low potential of 1.49 V (vs RHE) in 1 M potassium hydroxide. The Fe2O3/FeS electrocatalyst drives OER with a current density of 40 mA cm?2 at overpotential of 370 mV and a Tafel slope of 90 mV dec?1. Its performance is better than its counterparts (Fe2O3 and FeS) under similar electrochemical conditions. At an applied potential of 1.65 V (vs RHE), continuous oxygen production for several hours revealed the long-term stability and effective activity of the Fe2O3/FeS electrocatalyst for OER. The as-developed Fe2O3/FeS heterostructure provides an effective alternative low-cost metal-based electrocatalysts for OER.  相似文献   

13.
Recently, the replacement of expensive platinum-based catalytic materials with non-precious metal materials to electrolyze water for hydrogen separation has attracted much attention. In this work, Ni0.85Se, MoS2 and their composite Ni0.85Se/MoS2 with different mole ratios are prepared successfully, as electrocatalysts to catalyze the hydrogen evolution reaction (HER) in water splitting. The result shows that MoS2/Ni0.85Se with a molar ratio of Mo/Ni = 30 (denoted as M30) has the best catalytic performance towards HER, with the lowest overpotential of 118 mV at 10 mA cm−2, smallest Tafel slope of 49 mV·dec−1 among all the synthesized materials. Long-term electrochemical testing shows that M30 has good stability for HER over at least 30 h. These results maybe due to the large electrochemical active surface area and high conductivity. This work shows that transition metal selenides and sulfides can form effective electrocatalyst for HER.  相似文献   

14.
In this study, cobalt disulfide (CoS2) nanostructures are synthesized using a simple hydrothermal method. The effects of experimental parameters including cobalt precursor, reaction times, and reaction temperatures are investigated on the structure, morphology and electrocatalytic properties of CoS2 for hydrogen evolution reaction (HER). The characterization of as-prepared catalysts is performed using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The HER efficiency of the catalysts is examined using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) methods in 0.5 M H2SO4 solution. Furthermore, chronoamperometry (CA) is used for stability evaluation. The catalyst obtained from cobalt acetate precursor, within 24 h at 200 °C exhibits superior electrocatalytic activity with a low onset potential (139.3 mV), low overpotential (197.3 mV) at 10 mA. cm?2 and a small Tafel slope of 29.9 mV dec?1. This study is a step toward understanding the effect of experimental parameters of the hydrothermal method on HER performance and developing optimal design approaches for the synthesis of CoS2 as a common electrocatalyst.  相似文献   

15.
In order to solve the problem of large overpotential in water electrolysis for hydrogen production, transition metal sulfides are promising bifunctional electrocatalysts for hydrogen evolution reaction/oxygen evolution reaction that can significantly reduce overpotential. In this work, Ni3S2 and amorphous MoSx nanorods directly grown on Ni foam (Ni3S2-MoSx/NF) were prepared via one-step solvothermal process, which were used as a high-efficient electrocatalyst for overall water splitting. The Ni3S2-MoSx/NF composite exhibits very low overpotentials of 65 and 312 mV to reach 10 mA cm−2 and 50 mA cm−2 in 1.0 M KOH for HER and OER, respectively. Besides, it exhibits a low Tafel slope (81 mV dec−1 for HER, 103 mV dec−1 for OER), high exchange current density (1.51 mA cm−2 for HER, 0.26 mA cm−2 for OER), and remarkable long-term cycle stability. This work provides new perspective for further the development of highly effective non-noble-metal materials in the energy field.  相似文献   

16.
Synthesis of mixed transition metal nitrides often leads to the formation of more than one phases in the final product. A control over molar ratio of metals (Fe:Ni) along with synthetic strategy is used to form phase pure product (Fe3Ni7N@C). The synthesized material is used as an efficient and cost-effective electrocatalyst for oxygen evolution reaction (OER). Fe3Ni7N@C requires a low overpotential of 290 mV to achieve a catalytic current density of 10 mA cm−2 which holds Tafel slope of 40 mV dec−1 superior to the noble metal benchmark catalysts. The physicochemical integrity of Fe3Ni7N@C is maintained up to 12 h activity as evident from post catalytic characterization.  相似文献   

17.
Self-standing and hybrid MoS2/Ni3S2 foam is fabricated as electrocatalyst for hydrogen evolution reaction (HER) in alkaline medium. The Ni3S2 foam with a unique surface morphology results from the sulfurization of Ni foam showing a truncated-hexagonal stacked sheets morphology. A simple dip coating of MoS2 on the sulfurized Ni foam results in the formation of self-standing and hybrid electrocatalyst. The electrocatalytic HER performance was evaluated using the standard three-electrode setup in the de-aerated 1 M KOH solution. The electrocatalyst shows an overpotential of 190 mV at ?10 mA/cm2 with a Tafel slope of 65.6 mV/dec. An increased surface roughness originated from the unique morphology enhances the HER performance of the electrocatalyst. A density functional approach shows that, the hybrid MoS2/Ni3S2 heterostructure synergistically favors the hydrogen adsorption-desorption steps. The hybrid electrocatalyst shows an excellent stability under the HER condition for 12 h without any performance degradation.  相似文献   

18.
Efficient electrocatalyst for alkaline oxygen evolution reaction is the critical core to the wide application of metal-air energy storage and water electrolysis hydrogen energy. Therefore, appropriate design of highly active and stable non-noble metal oxygen evolution electrocatalyst with good electronic structure and multilevel structure is both a goal and a challenge. Here, we report a Fe–Ni2P electrocatalyst (NiFeP-MOF) with multilevel structure, which was obtained by anion exchange on the basis of Fe–Ni(OH)2 (NiFe-MOF) grown on nickel foam in situ by solvothermal method. As expected, Fe substitution regulates the Ni oxidation state in the NiFeP-MOF and realizes electronic structure coupling, showing a highly active and stable oxygen evolution reaction (OER) in alkaline electrolyte solution. Specifically, the NiFeP-MOF demonstrates an ultralow overpotentials (232 mV, 10 mA cm?2; 267 mV 100 mA cm?2), respectively, an extremely small Tafel slope (34 mV dec?1). Separately, the electrocatalyst shows an excellent cycle stability at 10 mA cm?2 for 12 h (43,200 s). More importantly, this work come up with an available policy for the preparation of excellent alkaline hydrolysis electrolysis catalysts and air cathodes with excellent performance.  相似文献   

19.
Developing high-efficiency and earth-abundant electrocatalysts for electrochemical water splitting is of paramount importance for energy conversion. Although tremendous effort has been paid to transition metal (TM) material-based electrocatalysts, rational design and controllable synthesis of fine structures to fully utilize the latent potential of TM materials remain great challenges. We herein report a composition-tuning strategy to achieve rational structure control of quaternary Co–Ni–S–Se materials through a facile one-pot hydrothermal method, in which earth-abundant Ni is introduced into a CoSxSe2-x matrix to optimize the morphology and electronic structure of the quaternary electrocatalyst. Because of the introduction of Ni, this novel Co–Ni–S–Se quaternary system shows better catalytic activity for water splitting with Tafel slopes of 42.1 mV dec−1 for hydrogen evolution reaction (HER) and 65.5 mV dec−1 for oxygen evolution reaction (OER), respectively, compared with its precursor Co–S–Se ternary system. For stability, there is negligible fading after long-term electrochemical test. Our work not only provides a novel thinking to introduce nickel into Co–S–Se ternary system by a facile hydrothermal synthesis for electrochemical water splitting, but also this quaternary system realizes bifunctional catalysis and better electrochemical performance relative to the ternary counterpart.  相似文献   

20.
It is essential to search highly active, steady and cheap non-noble electrocatalyst for hydrogen evolution reaction (HER). At present, nickel phosphides are extensively used in electrochemical hydrogen evolution due to its excellent stability and activity. Hence, we report a facile, effective and feasible strategy to synthesis of Ni5P4 nanosheets/nanoparticles structure on carbon cloth, which was fabricated by electroless nickel plating on carbon cloth followed via straightforward thermal phosphidation treatment with NaH2PO2 as phosphorus source. The as-prepared CC@Ni–P electrocatalyst exhibits HER activity with low overpotentials (93 mV vs. RHE) to attain current density 10 mA/cm2 as well as small Tafel slope (58.2 mV/dec), which outperforms most nickel phosphides electrocatalysts. The excellent HER performance can be ascribed to the large electrochemically active surface area, and phosphorus-rich Ni5P4 phase can supply further bridges sites of Ni and P. Significantly, as-prepared CC@Ni–P catalyst electrode exhibits no apparent HER activity decay after continuous stability test. Beyond that, the approach can be readily used to fabricate large size (5 × 5 cm) nickel phosphide electrocatalyst with excellent HER performance, which may be conducive to the proton exchange membrane (PEM) water electrolyser applications in future. This work opens an effective way to construct excellent performance transition-metal phosphides for HER.  相似文献   

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