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1.
In targeting the most important energy and environmental issues in current society, the development of low-cost, bifunctional electrocatalysts for urea-assisted electrocatalytic hydrogen (H2) production is an urgent and challenging task. In this work, interlaced rosette-like MoS2/Ni3S2/NiFe-layered double hydroxide/nickel foam (LDH/NF) is successfully synthesized by a two-step hydrothermal reaction. Due to its unique interlaced heterostructure, MoS2/Ni3S2/NiFe-LDH/NF exhibits excellent bifunctional catalytic activity towards the urea oxidation reaction (UOR) and the hydrogen evolution reaction (HER) in 1.0 M KOH with 0.5 M urea. In a concurrent two-electrode electrolyser (MoS2/Ni3S2/NiFe-LDH/NF(+,-)), only voltage of 1.343 V is required to reach 50 mA cm−2, which is 216 mV lower than for pure water splitting. Furthermore, after 16 h of urea electrolysis in 1.0 M KOH with 0.5 M urea, the current density remains at 98% of the original value. Thus, the catalyst is not only favorable for H2 production, but also has great significance for the problem of urea-rich wastewater treatment.  相似文献   

2.
Designing and optimizing structure is an effective method to enhance electrocatalytic performance of transition metal-based catalysts. In this work, an innovative nanostructured electrode, consisted of peapod-like Ni2P@N-doped carbon nanorods array coating on carbon fiber (CF@p-Ni2P@NC), is devised and synthesized. The N-doped carbon layer is crucial for maintaining the peapod-like nanostructure, which allows for multi-channel electrolyte transport and gas product release. And the carbon layer coating Ni2P nanoparticles also enhance electrical conductivity and stability, thus ensuring fast electron transport from/to active sites and the long-term stability of catalyst during urea oxidation reaction (UOR)/hydrogen evolution reaction (HER). Benefit from the reasonable structure, CF@p-Ni2P@NC present perfect performance with getting 100 mA cm?2 at potential/overpotential of 1.417/0.194 V for UOR/HER in 1.0 M KOH containing 0.5 M urea. In addition, the overall urea-electrolysis system using CF@p-Ni2P@NC bifunctional electrode only requires 1.590 V to obtain 100 mA cm?2.  相似文献   

3.
Finding a suitable replacement for the high potential of anodic water electrolysis (oxygen evolution reaction (OER)) is significant for hydrogen energy storage and conversion. In this work, a simple and scalable method synthesizes a structurally unique Ni3N nanoarray on Ni foam, Ni3N-350/NF, that provides efficient electrocatalysis for the urea oxidation reaction (UOR) that transports 10 mA cm−2 at a low potential of 1.34 V. In addition, Ni3N-350/NF exhibits electro-defense electrocatalytic performance for hydrogen evolution reaction, which provides a low overpotential of 128 mV at 10 mA cm−2. As proof of concept, all-water-urea electrolysis measurement is carried out in 1 M KOH with 0.5 M Urea with Ni3N-350/NF as cathode and anode respectively. Ni3N-350/NF||Ni3N-350/NF electrode can provide 100 mA cm−2 at a voltage of only 1.51 V, 160 mV less than that of water electrolysis, which proves its commercial viability in energy-saving hydrogen production.  相似文献   

4.
Energy-efficient production of hydrogen through urea electrolysis is still challenging due to the lack of satisfactory catalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) in urea containing solution. In this study, Ni–WxC/C (x = 1,2) composite with high activity for urea electrocatalysis was prepared by direct electro-reduction of affordable feedstock of NiO–CaWO4–C in molten CaCl2–NaCl at 873–973 K. The addition of graphite in precursor decreases the particle size of Ni. Introducing WxC into Ni particles can reduce the overpotential for UOR. As a result, the obtained Ni-WxC/graphite composite exhibits high current density for urea oxidation, which is about 11-folds and 52-folds higher than that of Ni/graphite and Ni (@1.53 V vs. RHE), respectively. After changing the carbon source from graphite to CNTs, the anodic current density was further increased by 43%, reaching 50.31 mA cm?2. Moreover, the cathodic catalyst WxC/CNTs obtained by the same preparation process exhibits high performance towards HER, with a low onset potential of 131.5 mV and a Tafel slope of 69.5 mV dec?1. Assembling an electrolyzer using Ni-WxC/CNTs as anode and WxC/CNTs as cathode can yield a current density of 10 mA cm?2 at merely 1.65 V in 1 M KOH/0.33 M urea aqueous solution, with excellent long-term electrochemical durability. The environmental-friendly production process uses affordable feedstocks for the synthesis of efficient catalysts toward urea electrolysis, promising an energy-saving hydrogen production as well as waste treatment.  相似文献   

5.
Developing efficient, stable and ideal urea oxide (UOR) electrocatalyst is key to produce green hydrogen in an economical way. Herein, Ru doped three dimensional (3D) porous Ni3N spheres, with tannic acid (TA) and urea as the carbon and nitrogen resources, is synthesized via hydrothermal and low-temperature treated process (Ru–Ni3N@NC). The porous nanostructure of Ni3N and the nickel foam provide abundant active sites and channel during catalytic process. Moreover, Ru doping and rich defects favor to boost the reaction kinetics by optimizing the adsorption/desorption or dissociation of intermediates and reactants. The above advantages enable Ru–Ni3N@NC to have good bifunctional catalytic performance in alkaline media. Only 43 and 270 mV overpotentials are required for hydrogen evolution (HER) and oxygen evolution (OER) reactions to drive a current of 10 mA cm?2. Moreover, it also showed good electrocatalytic performance in neutral and alkaline seawater electrolytes for HER with 134 mV to drive 10 mA cm?2 and 83 mV to drive 100 mA cm?2, respectively. Remarkably, the as-designed Ru–Ni3N@NC also owns extraordinary catalytic activity and stability toward UOR. Moreover, using the synthesized Ru–Ni3N@NC nanomaterial as the anode and cathode of urea assisted water decomposition, a small potential of 1.41 V was required to reach 10 mA cm?2. It can also be powered by sustainable energy sources such as wind, solar and thermal energies. In order to make better use of the earth's abundant resources, this work provides a new way to develop multi-functional green electrocatalysts.  相似文献   

6.
Electrodeposition provides a simple but effective way to prepare advanced electrode for the application in electrochemical field. In this work, NiMoSe ternary nanospheres were deposited on nickel foam (NiMoSe/NF) by one-step electrodeposition. The morphology, phase and chemical composition of the electrode was characterized by using SEM, TEM, XRD and XPS. The electrode exhibited excellent performance for both urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). It only required 1.39 V and 81 mV (vs. RHE) to deliver a current density of 10 mA/cm2 for UOR and HER, respectively. The electrolyzer constructed with NiMoSe/NF as both anode and cathode could deliver a current density of 10 mA/cm2 at a driving potential of 1.44 V. The stability test showed that the electrode had good durability as electrode for both UOR and HER. Considering the easiness, simplicity and low cost, the NiMoSe/NF electrode could find wide application in urea electrolysis.  相似文献   

7.
Replacing dynamics-restricted oxygen evolution reaction (OER) with smart urea oxidation reaction (UOR) is very important for reducing the power consumption for hydrogen production. Here, the Co3Mo3N-400/NF is prepared using a facial way, which exhibits remarkable catalytic performances for UOR, hydrogen evolution reaction (HER) and overall urea electrolysis (OUE) because of the more exposed active sites and high electrical conductivity. At 100 mA/cm2, the Co3Mo3N-400/NF shows a small potential of 1.356 V vs. RHE (reversible hydrogen electrode) for UOR, which is much lower than that for OER. Furthermore, for HER, to reach to 100 mA/cm2, a low overpotential of 299 mV is required, and the urea has negligible influence on the HER process. For OUE, the Co3Mo3N-400/NF||Co3Mo3N-400/NF shows a small cell potential of 1.481 V at 100 mA/cm2 along with a good durability. Our work provides more choice for future OUE to generate hydrogen.  相似文献   

8.
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   

9.
Defect and interface engineering has been established as efficient methods for altering the electrical structure and improving the activity of electrocatalysts. Here, a rational design architecture consisting of Ni2P nanoparticles embedded in P-doped carbonized wood fibers (Ni2P/PCWF) is synthesized by simultaneous carbonization and phosphorization. A synergistic enhancement effect between electronic structure manipulation and interface regulation is observed in Ni2P/PCWF during the urea oxidation reaction (UOR). First, the P doping of carbon can optimize the electronic structure of Ni2P/PCWF. Second, the charge transport process is aided by the Ni2P nanoparticles embedded in the PCWF. Lastly, electron transfer can be accelerated by the in-situ formed heterogeneous interface between metal phosphides and metal hydroxides (hydroxyl oxides). Due to the synergy of the structural and electrical modulation, Ni2P/PCWF exhibits remarkable electrocatalytic properties toward the UOR under alkaline conditions. It only requires 1.34 V (vs. RHE) to achieve a current density of 50 mA cm?2, and the increase in potential at 10 mA cm?2 for 70 h is insignificant (≈2.9%). This work supports the development of new strategies using sustainable, renewable wood fibers to develop excellent UOR catalysts for energy-saving H2 generation.  相似文献   

10.
The anode oxygen evolution reaction (OER) is a delayed half-reaction of water splitting that requires a relatively high overpotential. Therefore, a more easily oxidized urea oxidation reaction (UOR) has been implemented to replace OER. Co–Mo-based bimetallic oxides have been recognized as interesting candidates for electrocatalytic water splitting due to their unique d electron configurations, but the low conductivity and limited active sites still hinder their development. Herein, we demonstrated that anion-modulation in CoMoO4 nanoplates as coupled hydrogen evolution reaction (HER) and UOR for convenient and efficient urea-assisted hydrogen-production system are demonstrated. The findings of the experiments show that nitrogen doping and phosphorus doping exhibit excellent activity toward alkaline HER and UOR, respectively. As a result, the N–CoMoO4 and P–CoMoO4 electrode exhibit low potentials of ?0.062 V and 1.251 V (vs. RHE) to reach a current of 10 mA cm?2 for HER and UOR. The full urea electrolysis is driven by N–CoMoO4||P–CoMoO4 executes stably for 24 h at a low potential of 1.41 V. This is a unique anion-modulation method in electrocatalysts to combine hydrogen generation and sewage treatment, which could pave the way for the creation of long-term energy conversion systems.  相似文献   

11.
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   

12.
The development of high-performance, low-cost, and non-noble metal catalysts for the urea oxidation reaction (UOR) as an alternative to oxygen evolution reaction (OER) has received much attention but remains a huge challenge. In this work, NiSe2/TiN@Ni12P5/NF catalysts with a stalactite structure were prepared by chemical vapor deposition to obtain the integrated electrode Ni12P5/NF on the nickel foam (NF), and subsequently NiSe2/TiN was formed on the Ni12P5/NF surface by the hydrothermal method. The designed catalyst delivers an ultra-low potential of 1.270 V at 10 mA cm?2, and a Tafel slope of 33.3 mV dec?1 for UOR. Furthermore, the catalyst only shows a 1.7% decrease in potential after an 80-h stability test, which demonstrates its excellent stability. The prepared NiSe2/TiN@Ni12P5/NF shows a high specific surface area, and the strengthening effect between TiN and NiSe2, endowing the catalyst a high activity and durability.  相似文献   

13.
Reasonable design and preparation of non-noble metal electrocatalysts with predominant catalytic activity and long-term stability for oxygen evolution reaction (OER) are essential for electrocatalytic water splitting. Ni foam (NF) is highlighted for its 3D porous structure, impressive conductivity and large specific surface area. Herein, nano/micro structured dendritic cobalt activated nickel sulfide grown on 3D porous NF (Co–Ni3S2/NF) has been successfully synthesized by one-step hydrothermal method. Due to the ingenious incorporation of Co, Co–Ni3S2/NF electrode shows auspicious electrocatalytic performance for OER compared with Ni3S2/NF electrode. As a result, Co–Ni3S2/NF needs overpotential of only 274 and 459 mV at current density of 10 and 50 mA cm−2, respectively, while Ni3S2/NF requires overpotential of 344 and 511 mV. At potential of 2.0 V (vs. RHE), Co–Ni3S2/NF displays current density of 191 mA cm−2, while Ni3S2/NF just attains current density of only 135 mA cm−2. Moreover, Co–Ni3S2/NF demonstrates excellent stability for uninterrupted OER in alkaline electrolyte. The strategy of designing and preparing cobalt activated nickel sulfide grown on NF renders a magnificent prospect for the development of metal-sulfide-based oxygen evolution catalysts with excellent electrocatalytic performances.  相似文献   

14.
In recent years, the exploration of efficient and stable noble-metal-free electrocatalysts is becoming increasingly important, used mainly for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, a new ultrathin porous Cu1-xNixS/NF nanosheets array was constructed on the 3D nickel skeleton by two-step method: hydrothermal method and vulcanization method. Through these two processes, Cu1-xNixS/NF has a larger specific surface area than that of foamed nickel (NF) and Cu1-xNixO/NF. The Cu1-xNixS/NF materials show excellent catalytic activity by accelerating the electron transfer rate and increase the amount of H2 and O2 produced. The lower overpotential was obtained only 350 mV at 20 mA cm−2 for OER, not only that, but also the same phenomenon is pointed out in HER, optimal Cu1-xNixS/NF presents low overpotentials of 189 mV to reach a current density of 10 mA cm−2 in 1.0 M KOH for HER. Both OER and HER shows a lower Tafel slope: 51.2 mV dec−1 and 127.2 mV dec−1, subsequently, the overall water splitting activity of Cu1-xNixS/NF was investigated, and the low cell voltage was 1.64 V (current density 10 mA cm−2). It can be stable for 14 h during the overall water splitting reaction. These results fully demonstrate that Cu1-xNixS/NF non-precious metal materials can be invoked become one of the effective catalysts for overall water splitting, providing a richer resource for energy storage.  相似文献   

15.
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   

16.
Developing non-noble metal catalysts with excellent electrocatalytic performance and stability is of great significance to hydrogen production by water electrolysis, but there are still problems of low activity, complex preparation and high cost. Herein, we fabricated a novel Ni3S2/Ni(OH)2 dual-functional electrocatalyst by a one-step fast electrodeposition on nickel foam (NF). While maintaining the electrocatalytic performance of Ni3S2, the existence of heterostructure and Ni(OH)2 co-catalyst function greatly improves the overall water splitting performance of Ni3S2/Ni(OH)2–NF. Hence, It shows a low overpotential of 66 mV at 10 mA cm?2 for HER and 249 mV at 20 mA cm?2 for OER. The dual-functional electrocatalyst needs only 1.58 V at 20 mA cm?2 when assembled two-electrode electrolytic cell. Impressively, the electrocatalyst also shows outstanding catalytic stability for about 800 h when 20 and 50 mA cm?2 constant current was applied, respectively which demonstrates a potential electrocatalyst for overall water splitting.  相似文献   

17.
The electrochemical oxidation of urea and hydrazine over self-supported Fe-doped Ni3S2/NF (Fe–Ni3S2/NF) nanostructured material is presented. Among the various reaction conditions Fe–Ni3S2/NF-2 prepared at 160 °C for 8 h using 0.03 mM Fe(NO3)3 shows the best results for the hydrazine and urea oxidation reactions. The potential values of 0.36, 1.39, and 1.59 V are required to achieve the current density of the 100 mA cm?2 in 1 M hydrazine (Hz), 0.33 M urea, and 1 M KOH electrolyte, respectively. The onset potential in 1 M KOH, 0.33 M Urea +1 M KOH, and 1 M Hz + 1 M KOH values are 1.528, 1.306, and 0.176 respectively. The Fe–Ni3S2/NF-2 shows stable performance at 10 mA cm?2 until 50 h and at 60 mA cm?2 over the 25 h. A cell of PtC//Fe–Ni3S2/NF-2 requires the potential of 0.49, 1.46, and 1.59 V for the hydrogen production in 1 M Hz + 1 M KOH, 0.33 M Urea +1 M KOH, and 1 M KOH electrolyte, respectively, at a current density of 10 mA cm?2, and almost 90% stable for the hydrogen production over the 80 h in all electrolytes. The improvement of the chemical kinetics of urea and hydrazine oxidation is due to the synergistic effect of the adsorption and fast electron transfer reaction on Fe–Ni3S2/NF-2. The doped Fe ion facilitates the fast electron transfer and the surface of Ni3S2 support to the urea and hydrazine molecule adsorption.  相似文献   

18.
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   

19.
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   

20.
Electrochemical water splitting to produce hydrogen is one of the most important technologies for energy storage and conversion. Urea oxidation reaction (UOR) with a lower electrode potential instead of oxygen evolution reaction (OER, water-splitting anode) in the water-urea electrolysis is an energy-saving approach. In this paper, NiMoO4–Ni(OH)2/NF is synthesized by hydrothermal reactions and explored as both hydrogen evolution reaction (HER) and UOR catalyst electrodes. This composite catalyst shows high catalytic bifunctional activities towards both HER and UOR. To validate both catalytic UOR and HER activities and durability, a two-electrode water-urea electrolyzer composed of NiMoO4–Ni(OH)2/NF as both anode and cathode materials is constructed (NiMoO4–Ni(OH)2/NF||NiMoO4–Ni(OH)2). Experiments show that a voltage of 1.341 V with a high stability (over 3000 CV cycles) can be achieved at 10 mA cm−2, which are much better than those obtained using a Pt/C||IrO2.  相似文献   

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