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1.
Alkaline water electrolysis is a promising strategy for the production of hydrogen and oxygen. However, developing high-efficiency non-precious electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is still a big challenge. Here, we report a nickel foam-based electrode coated with NiCoV-LDH and NiCo-LDH nanosheets (denoted as NiCo-LDH@NiCoV-LDH/NF) by a two-step method for efficient water splitting performance. The NiCo-LDH@NiCoV-LDH/NF with unique nanosheet-on-nanosheet construction can enlarge the electrochemical active specific surface area greatly, and thus accelerate the charge transfer of electrocatalytic reactions. Besides, the doping of vanadium could also improve the OER performance. The electrode only requires a low overpotential for OER (260 mV at 100 mA cm?2), and HER (80 mV at 10 mA cm?2) reactions in 1.0 mol/L KOH solution at room temperature. Furthermore, in the two-electrode water splitting test, a current density of 10 mA cm?2 was achieved at 1.55 V using 1.0 mol/L KOH solution, with excellent durability of 40 h. This work provided a facile method for developing new bifunctional catalysts.  相似文献   

2.
The development of hydrogen evolution activity (HER) electrocatalyst that can run durably and efficiently under the large current density is of special significance but still challengeable for the massive production of hydrogen. Herein, a CoP/Ni(OH)2 nanowire catalysts grown on Co foam (CF) with a three-dimensional heterojunction structure has been successfully prepared by electrodepositing nickel hydroxide on the surface of cobalt phosphide. The prepared CoP/Ni(OH)2–15 min sample reveals a superior HER activity and stability. It merely requires ultralow overpotentials of 108 and 175 mV to 100 and 500 mA cm?2, respectively. In addition, the long-term stability test shows that the catalyst (CoP/Ni(OH)2–15 min) can operate stably for at least 70 h at 400 mA cm?2. Utilizing NiFe-LDH/IF with high OER activity, the NiFe-LDH/IF || CoP/Ni(OH)2–15 min catalyst system possesses the same outstanding performance for overall water splitting (OWS), which can accomplish ≈ 500 mA cm?2 at 1.74 V in 1 M KOH electrolyte. Moreover, the NiFe-LDH/IF || CoP/Ni(OH)2–15 min couple can work for more than 80 h at 500 mA cm?2, indicating its a great prospect in the area of electrolysis water. Such excellent catalytic performance is mainly attributed to the armor effect of Ni(OH)2, which can not only promote the rapid decomposition of water molecules, but also prevent the loss of phosphorus and enhance the synergistic effect of CoP and Ni(OH)2. This work can offer a significant reference for the design with high-performance and durable transition metal phosphide electrocatalysts.  相似文献   

3.
Water splitting is an efficient strategy to produce purity hydrogen and convert intermittent electricity from renewable wind and solar sources. In this work, dense NiMoO4 micro-pillars arrays (MPAs) were in-situ grown on nickel foam (NF) through facile hydrothermal method, then the NiMoO4/NF were converted into NiMoO4–P/NF and NiFe/NiMoO4/NF via phosphating and electrodeposition method, respectively. The NiMoO4–P/NF electrode required small overpotentials of 34 mV@10 mA cm−2 and 130 mV@100 mA cm−2 for hydrogen evolution reaction (HER). The NiFe/NiMoO4/NF electrode exhibited excellent oxygen evolution reaction (OER) activity with overpotentials of 210 mV@10 mA cm−2 and 300 mV@100 mA cm−2. The overall water splitting using the anode-cathode couple of NiFe/NiMoO4/NF||NiMoO4–P/NF only consumes low voltages of 1.47 V@10 mA cm−2 for 100 h and 1.66 V@100 mA cm−2 for 50 h in 1 M KOH. The electronic modification and the well-designed hierarchical structure contribute the high energy-efficient and stabile overall water splitting.  相似文献   

4.
The synthesis of high performance and economical electrocatalysts in the process of overall water splitting is very important for the production of hydrogen energy and has become one of the most important challenges. Here, various Ni, Ni–Fe, Ni–Mn nanosheets and Ni–Fe–Mn ternary nanosheets were created using cost-effective, versatile and binder-free electrochemical deposition methods, and the electrocatalytic activity of various electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were investigated in an alkaline environment. Due to the high electrochemical active surface area due to the fabrication of nanosheets, the synergistic effect between different elements on the electronic structure, the high wettability due to the formation of nanosheets and the quick detachment of formed gasses from the electrode, the Ni–Fe–Mn nanosheets electrode showed excellent electrocatalytic activity. In order to deliver the 10 mA cm−2 current density in HER and OER processes, this electrode required values of 64 mV and 230 mV overpotential, respectively. Also, the stability test showed that after 10 h of electrolysis at a current density of 100 mA cm−2, the overpotential changes was very small (less than 4%), indicating that the electrode was excellent electrostatic stability. Also, when using as a bi-functional electrode in the full water splitting system, it only needed a cell voltage of 1528 V to deliver a current of 10 mA cm−2. The results of this study indicate a new strategy for the synthesis of active and stable electrocatalysts.  相似文献   

5.
Designing cost-effective bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline electrolyte remains a significant challenge. Herein, we report adding Nb to pristine CoP nanowires enhances the material's catalytic activities towards HER and OER. Density functional theory (DFT) calculation unravels that the Nb atoms not only optimize hydrogen binding abilities on CoP surface, but also modulate the surface electron densities of in situ formed β-CoOOH during anodic oxidation, thereby greatly accelerate both the HER and OER kinetics in alkaline solutions. In addition, an alkaline electrolyzer using Nb-doped CoP nanowires as cathode and anode for overall water splitting, delivers 100 mA cm?2 at low cell voltage of 1.70 V, superior to Pt//RuO2 couple. This doping strategy can be extended to other transition metal phosphides as multifunctional catalysts towards overall water splitting and beyond.  相似文献   

6.
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   

7.
Searching high-active, stable and abundant bifunctional catalysts to replace noble metals for hydrogen and oxygen evolution reactions (HER and OER) is desired. Herein, petal-like NiCoP sheets were synthesized on carbon paper covered with a 3D nitrogen-doped carbon nanofiber network (NiCoP/CNNCP) by a simple hydrothermal process followed by phosphorization. The HER overpotential in 0.5 M H2SO4 and OER overpotential in 1 M KOH of the NiCoP/CNNCP electrode only required 55 mV and 260 mV to drive a current density of 10 mA cm?2, respectively, which was comparable or even better than most nickel-and cobalt-based phosphide catalysts. The overall water-splitting electrolyzer with an asymmetric electrolyte system assembled using NiCoP/CNNCP as bifunctional electrodes required an extremely low cell voltage of 1.04 V to achieve a current density of 10 mA cm?2, which was much lower than almost all alkaline electrolysis systems.  相似文献   

8.
Developing robust non-noble catalysts towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is vital for large-scale hydrogen production from electrochemical water splitting. Here, we synthesize Sn- and Fe-containing sulfides and oxyhydroxides anchored on nickel foam (SnFeSxOy/NF) using a solvothermal method, in which a heterostructure is generated between the sulfides and oxyhydroxides. The SnFeSxOy/NF exhibits low overpotentials of 85, 167, 249, and 324 mV at 10, 100, 500 and 1000 mA cm?2 for the HER, respectively, and a low overpotential of only 281 mV at 100 mA cm?2 for the OER. When it serves as both anode and cathode to assemble an electrolyzer, the cell voltage is only 1.69 V at 50 mA cm?2. The sulfides should be the efficient active species for the HER, while the oxyhydroxides are highly active for the OER. The unique sulfide/oxyhydroxide heterostructure facilitates charge transfer and lowers reaction barrier, thus promoting electrocatalytic processes.  相似文献   

9.
Exploring earth-abundant bifunctional electrocatalysts with highly efficient activity for overall water splitting is exceedingly challenging. Herein, a facile electrodeposit-phosphating-electrodeposit strategy is developed to obtain Mo-doped Co(OH)2 nanofilms coupled with CoP nanosheets loaded on nickel foam (denoted as MoCo(OH)2/CoP/NF). Benefitting from the unique structural merits, MoCo(OH)2/CoP/NF exhibits outstanding electrocatalytic performance both for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The results indicate that the dopant of Mo in the Co(OH)2 can further improve the electrocatalytic performance. To achieve a current density of 10 mA cm?2, only 15 and 287 mV are required for HER and OER in 1 M KOH solution, respectively. When MoCo(OH)2/CoP/NF simultaneously employed as cathode and anode for overall water splitting, it only requires 1.593 and 1.853 V to achieve 10 and 50 mA cm?2, respectively. The electrocatalytic activity of MoCo(OH)2/CoP/NF for overall water splitting even exceed the benchmark electrode couple of Pt/C/NF||RuO2/NF, and MoCo(OH)2/CoP/NF perform excellent durability for overall water splitting. This work opens up new avenues for large-scale commercial production of overall water splitting catalysts due to its low-cost and facile method.  相似文献   

10.
The construction of cost-effective bifunctional electrocatalysts with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant for efficient overall water splitting. Herein, this work demonstrates a novel strategy for the synthesis of nickel-cobalt oxides/sulfides/phosphides composite (denoted as NiCoO–2P/S) nanoarrays on Ni foam. In this method, Ni–Co bimetallic oxide nanowires on Ni foam were partially phosphorized and sulfurized simultaneously in situ to yield Ni–Co oxide/sulfide/phosphide composite. The NiCoO–2P/S arrays have good interfacial effects and display many holes in the nanowires, giving it the advantage of large accessible surfaces on the nanowires and a beneficial for the release of gas bubbles, resulting in an excellent OER performance with a low overpotential (η) of 254 mV at 100 mA cm?2 and good HER activity (η10 = 143 mV at 10 mA cm?2). The electrocatalytic test results demonstrate small Tafel slopes (82 mV dec?1 for HER, 88 mV dec?1 for OER) and the satisfying durability in an alkaline electrolyte, indicating that the HER and OER activity was enhanced by the introduction of the Ni/Co sulfides and phosphides into Ni–Co oxides composite nanowires. Furthermore, the as-prepared NiCoO–2P/S catalyst can be used as both the anode and the cathode simultaneously to realize overall water splitting in the two-electrode electrolyzer. This system can be driven at low cell voltages of 1.50 and 1.68 V to achieve current densities of 10 and 100 mA cm?2, respectively. This work provides an alternative strategy to prepare high-performance bifunctional electrochemical materials and demonstrates the advantages of Ni–Co oxide/sulfide/phosphide composites for water splitting.  相似文献   

11.
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   

12.
The growing hydrogen consumption has greatly promoted the development of efficient, stable and low-cost electrocatalysts for the hydrogen evolution reaction (HER). Constructing functional nanostructures is an efficacious strategy to optimize catalytic performance. Herein, we present a feasible route to fabricate distinctive 3D grass-like cobalt phosphide nanocones clad with mini-vesicles on the hierarchically porous Ni foam, which can directly serve as a binder-free electrocatalyst with superior catalytic activity and durability in HER. Thanks to its distinctive 3D microstructure featured with favourable pore-size distribution, abundant active sites provided by mini-vesicles and rapid electron transfer with the assistance of Ni foam, the as-grown grass-like CoP/NF electrocatalyst has shown a favourable overpotential in an acidic solution with an onset overpotential of ∼35 mV, an overpotential of 71 mV at a current density of 10 mA cm−2, reduced by 60 mV in comparison with that realized by urchin-like CoP/NF nanoprickles. Moreover, it has exhibited an excellent HER activity in the alkaline medium, with an overpotential of 117 mV at 10 mA cm−2, a Tafel slope of 63.0 mV dec−1 and a long-term electrochemical durability.  相似文献   

13.
Electrochemical hydrogen production from water splitting is one of the effective methods for hydrogen production that has recently attracted particular attention. One of the limitations of the electrochemical water splitting method is the slow oxygen evolution reaction (OER), which leads to an increase in overpotential and a decrease in hydrogen production efficiency. Here, Ni–Mo–S ultra-thin nanosheets were synthesized using the pulse reverse electrochemical deposition technique, and then this electrode was used as an electrode material for accelerating hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Remarkably, the optimized electrode needs only 74 mV to attain the 10 mA cm−2 current density in HER and require only 1.3 V vs RHE potential in the UOR process. Also, results showed that the replacement of the UOR with the OER process resulted in a significant improvement in the electrochemical production of hydrogen in which for delivering the current density of 10 mA cm−2 in overall urea electrolysis, only 1.384 V is needed. In addition, outstanding catalytic stability was obtained, after 50 h electrolysis, the voltage variation was negligible. Such outstanding catalytic activity and stability was due to 3-D ultrathin nanosheets, the synergistic effect between elements, and the superhydrophilic/superaerophobic nature of fabricated electrode.  相似文献   

14.
Electrocatalytic water splitting is a promising route for the generation of clean hydrogen. However, the anodic oxygen evolution reaction (OER) suffers greatly from low reaction kinetics and thereby hampers the energy efficiency of alkaline water electrolysers. In recent years, tremendous efforts have been dedicated to the pursuit of highly efficient, low cost and stable electrocatalysts for oxygen evolution reaction. Herein, an amorphous FeOOH roughened capillary-liked CoAl layered double hydroxide (LDH) catalyst grown on nickel foam (denoted as FeOOH–CoAl LDH/NF) was reported for OER electrolysis. The developed FeOOH–CoAl LDH/NF electrode shows excellent OER activity with overpotentials of 228 mV and 250 mV to deliver a current density of 50 mA cm?2 and 100 mA cm?2 in 1.0 M KOH solution, respectively, ranking it one of the most promising OER catalysts based on transition-metal-based LDH. This is owed to the formed capillary-liked hierarchy structure with high-porosity as well as the strong electronic interaction between FeOOH and CoAl LDH. The developed morphological engineering approach to build hierarchal porous structures together with facile amorphous FeOOH modification may be extended to other layered double hydroxide catalyst for enhanced OER activities.  相似文献   

15.
Developing the novel catalysts with an excellent performance of hydrogen generation is essential to facilitate the application of hydrogen evolution reaction (HER). Herein, a heterostructured cobalt phosphide/nickel phosphide/carbon cloth (CoP/Ni2P/CC) composite was fabricated via an interfacial engineering strategy to achieve the modification of CoP nanoleaf on Ni2P nanosheet skeleton supported by carbon cloth. By virtue of the unique heterostructure, abundant exposing active sites and the synergistic coupling effect of CoP and Ni2P nanoparticles, the elaborated CoP/Ni2P/CC composite exhibits a robust catalytic property. Among fabricated composites, the optimal CoP/Ni2P/CC-4 catalyst behaves an excellent HER performance at a wide pH range (overpotentials of 67, 71 and 95 mV to afford 10 mA cm?2 in 0.5 M H2SO4, 1 M KOH and 1 M PBS, respectively). The HER current density of this composite shows a negligible degradation after continuous test for 24 h. Charmingly, the HER process of this catalyst was innovatively applied to reduce graphene oxide, and thus exploiting the fabrication route of reduced graphene oxide (rGO). We are sure that this work will provide a firm guideline for the exploitation of pH-universal HER catalysts and the exploration of HER application.  相似文献   

16.
Searching for efficient, stable and low-cost nonprecious catalysts for oxygen and hydrogen evolution reactions (OER and HER) is highly desired in overall water splitting (OWS). Herein, presented is a nickel foam (NF)-supported MoS2/NiFeS2 heterostructure, as an efficient electrocatalyst for OER, HER and OWS. The MoS2/NiFeS2/NF catalyst achieves a 500 mA cm−2 current density at a small overpotential of 303 mV for OER, and 228 mV for HER. Assembled as an electrolyzer for OWS, such a MoS2/NiFeS2/NF heterostructure catalyst shows a quite low cell voltage (≈1.79 V) at 500 mA cm−2, which is among the best values of current non-noble metal electrocatalysts. Even at the extremely large current density of 1000 mA cm−2, the MoS2/NiFeS2/NF catalyst presents low overpotentials of 314 and 253 mV for OER and HER, respectively. Furthermore, MoS2/NiFeS2/NF shows a ceaseless durability over 25 h with almost no change in the cell voltage. The superior catalytic activity and stability at large current densities (>500 mA cm−2) far exceed the benchmark RuO2 and Pt/C catalysts. This work sheds a new light on the development of highly active and stable nonprecious electrocatalysts for industrial water electrolysis.  相似文献   

17.
A class of ruthenium-nickel alloy catalysts featured with nanoporous nanowires (NPNWs) were synthesized by a strategy combining rapid solidification with two-step dealloying. RuNi NPNWs exhibit excellent electrocatalytic activity and stability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in which the RuNi-2500 NPNWs catalyst shows an OER overpotential of 327 mV to deliver a current density of 10 mA cm?2 and the RuNi-0 NPNWs catalyst requires the overpotential of 69 mV at 10 mA cm?2 showing the best HER activity in alkaline media. Moreover, the RuNi-1500 NPNWs catalyst was used as the bifunctional electrocatalyst in a two-electrode alkaline electrolyzer for water splitting, which exhibits a low cell voltage of 1.553 V and a long-term stability of 24 h at 10 mA cm?2, demonstrating that the RuNi NPNWs catalysts can be considered as promising bifunctional alkaline electrocatalysts.  相似文献   

18.
The design and manufacture of effective non-noble metal catalysts for the H2 evolution reaction (HER) are urgent for realizing a cost-effective hydrogen production. We report herein on flower-like structures consisting of NiCoP–CoP heterostructural nanowires grown directly on the hierarchically porous nickel framework (NiCoP–CoP/Ni/NF) to achieve a highly efficient HER in alkaline solution (1.0 M KOH). The NiCoP–CoP/Ni/NF is synthesized by electrodeposition of porous Ni layers on Ni foam, followed by simple hydrothermal reaction and phosphorization. For HER, the binder-free NiCoP–CoP/Ni/NF electrode can reach 10 mA cm?2 current density at a quite low overpotential of 49 mV, because of the combination of porous Ni layers and highly active NiCoP–CoP nanowires. In addition, the NiCoP/CoP heterostructures exhibited remarkable stability under the long-term durability test. This work provides a new strategy that combines electrodeposition and hydrothermal reaction to synthesize effective HER catalysts.  相似文献   

19.
Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER).The electrodeposition process applied after the initial hydrothermal process provides a stable structure and, in addition, enhances the sluggish hydrogen evolution efficiency. In alkaline media, the developed electrode needs an overpotential of 48 and 188 mV to drive current densities (j) of 10 and 100 mA cm?2, respectively. After continuous 110 h electrochemical stability test under j = 150 mA cm?2 conditions, demonstrates an excellent stability with ignorable activity decrease. Such superior HER catalytic performance can be derived from the synergistic effect between Ni and Fe atoms, also exposure to a high number of active sites on the nanosheets, and good dynamic with effective electron transport along the nanosheets. The present work provides a promising route for the design and fabrication of cost-effective and highly efficient HER electrocatalysts.  相似文献   

20.
Developing highly efficient, durable and noble-metal-free electrocatalysts for hydrogen evolution reaction (HER) in a wide pH range is the key to achieve sustainable energy cycle. Modulating the electronic characteristics of catalysts is of great important to enhance their electrocatalytic performance. Herein, we successfully design a self-supported multi-element transition metal phosphide (V-CoP/Ni2P/NF) electrocatalyst by V-doping and interface engineering. According to DFT calculations, V dopants and the synergistic effect between CoP and Ni2P can bring optimal hydrogen/water adsorption free energies. Meanwhile, the 3D cross-linked network structure could expose abundant active sites and facilitate ions diffusion/electron transfer. As a result, the V-CoP/Ni2P/NF catalysts exhibit superior electrocatalytic activities with extremely low overpotentials of 20, 58 and 79 mV to deliver a current density of 10 mA cm?2 for HER in alkaline, neutral and acidic electrolytes, respectively. Moreover, they also display outstanding long-term stability. This electronic modulation strategy provides a promising pathway for energy-related catalysis processes.  相似文献   

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