Fine nickel powders with a narrow particle size distribution were prepared by reducing nickel hydroxide in aqueous solution.The formation and reduction pathways of nickel powder were analyzed,as well as the effects of...Fine nickel powders with a narrow particle size distribution were prepared by reducing nickel hydroxide in aqueous solution.The formation and reduction pathways of nickel powder were analyzed,as well as the effects of the molar ratio of hydrazine hydrate to nickel hydroxide,hydrazine concentration,and the dosage of surfactant PEG6000 on particle size,surface morphology,and dispersion.Results reveal that the nickel particle nucleation occurs on the nickel hydroxide surface,and the nickel hydroxide gradually dissolves during the reaction.With the increase in molar ratio of hydrazine hydrate to nickel hydroxide,the nickel particle size is initially decreased and then increased.Higher hydrazine hydrate concentrations result in smaller particle sizes.A small amount of PEG6000 surfactant can improve dispersion of nickel particles,but a higher amount of PEG6000 surfactant results in the maintenance of the morphology of nickel hydroxide.Adjusting the surfactant dosage can control the average particle size between 1-2μm.展开更多
Electrocatalysis has emerged as a sustainable approach for the selective oxidation of fatty alcohols to fatty acids,circumventing the environmental concerns associated with conventional routes.However,the low aqueous ...Electrocatalysis has emerged as a sustainable approach for the selective oxidation of fatty alcohols to fatty acids,circumventing the environmental concerns associated with conventional routes.However,the low aqueous solubility of hydrophobic fatty alcohols presents a major challenge.While nickel hydroxide(Ni(OH)_(2))serves as a cost-effective catalyst for alcohol oxidation,its hydrophilic nature limits substrate accessibility and mass transport,causing sluggish kinetics and competing oxygen evolution.Herein,we propose a hydrophobic interface engineering strategy via co-electrodeposition of Ni(OH)_(2)with polytetrafluoroethylene(PTFE),fabricating the composite electrode(ED-Ni(OH)_(2)-PTFE).The optimized electrode achieves 95%Faradaic efficiency for octanoic acid at 1.5 V vs.RHE,with a production rate 2–3 times higher than pristine Ni(OH)_(2).Mechanistic studies combining in situ Raman spectroscopy,fluorescence imaging,and coarse-grained molecular dynamics simulations reveal that PTFE selectively enriches octanol at the electrode-electrolyte interface by modulating interfacial hydrophobicity.A continuous-flow microreactor integrating anodic octanol oxidation with cathodic hydrogen evolution reduces cell voltage by~100 m V,achieving simultaneous fatty acid and hydrogen production.This work highlights the critical role of hydrophobic interfacial microenvironment design in organic electrosynthesis,offering a promising strategy for upgrading fatty alcohols under mild conditions.展开更多
Developing an efficient electrocatalyst for superior electrochemical water splitting(EWS)is crucial for achieving comprehensive hydrogen production.A heterostructured electrocatalyst,free of noble metals,Ti_(3)C_(2)MX...Developing an efficient electrocatalyst for superior electrochemical water splitting(EWS)is crucial for achieving comprehensive hydrogen production.A heterostructured electrocatalyst,free of noble metals,Ti_(3)C_(2)MXene nanosheet-integrated cobalt-doped nickel hydroxide(NHCoMX)composite was synthesized via a hydrothermal method.The abundant pores in the Ti_(3)C_(2)MXene nanosheet(MX)-integrated microarchitecture increased the number of active sites and facilitated charge transfer,thus enhancing electrocatalysis.Specifically,the MXenhanced charge transfer considerably transformed the microelectronic structure of cobalt-doped Ni(OH)2(NHCo),which promoted its hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Hence,as an EWS catalyst,NHCoMX exhibited an exceptional electrocatalytic activity,demonstrating OER and HER overpotentials of 310 mV and 73 mV,respectively,with low Tafel slopes of 65 mV dec^(-1)and 85 mV dec^(-1),respectively;it exhibited a current density of 10 mV cm^(-2)in 1.0 mol L^(-1)KOH,representing the closest efficiency to the noble state-of-the-art RuO2 and Pt/C catalyst.Furthermore,the developed electrocatalyst improved the activities of both HER and OER,leading to an overall EWS current density of 10 mA cm^(-2)at 1.72 V in an alkaline electrolyte with two electrodes.This study describes an efficient heterostructured NHCoMX composite electrocatalyst.It is significantly comparable to the noble state-of-the-art electrocatalysts and can be extended to fabricate resourceful catalysts for large-scale EWS applications.展开更多
Carbon-based materials exhibit excellent dielectric absorption properties,among which graphene has received particular attention in research of electromagnetic wave absorbing materials because of its high electrical c...Carbon-based materials exhibit excellent dielectric absorption properties,among which graphene has received particular attention in research of electromagnetic wave absorbing materials because of its high electrical conductivity and unique large-area,thin-layer two-dimensional structural features.However,the electromagnetic absorption performance of the material is hindered from further improvement due to its single component composition.It is influenced by the conductive network of graphene,making it challenging to achieve a balance in impedance matching and electromagnetic loss,thereby restricting its broader application.To address these challenges,we developed a series of nickel hydroxide-modified graphene composites.Through a structural composite design,we optimized overall impedance matching,introduced diverse loss mechanisms to enhance electromagnetic loss performance,and utilized a secondary reaction control method to precisely regulate the deposition of nickel hydroxide on the graphene surface,thereby achieving regulate of the composite material's electromagnetic parameters within a defined range.Under low sample filling ratios and a thin sample thickness of 1.8 mm,the effective absorption bandwidth reaches 6.5 GHz,demonstrating excellent electromagnetic absorption performance.This study provides a controllable design approach for modulating material electromagnetic parameters by influencing the reaction process.It also offers a design method for composites with an outstanding electromagnetic loss mechanism.展开更多
The oxidative energy storage behaviors of a designed novel system comprising a nickel hydroxide film electrode and an oxygen-reducing platinum cathode were investigated by various electrochemical techniques. The struc...The oxidative energy storage behaviors of a designed novel system comprising a nickel hydroxide film electrode and an oxygen-reducing platinum cathode were investigated by various electrochemical techniques. The structure and morphology of samples were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） analysis. It is found that the oxidative energy storage in the Ni（OH）2 electrodes can be obviously enhanced in the coupling system containing the cathode electrolytes with higher oxygen content or lower pH value. The results of the oxidation-discharge cycle tests show that the Ni（OH）2 film electrode oxidized in the coupling system with 1.0 mol/L Na2SO4 （pH=2） as cathode electrolyte for 600 s presents discharge capacities of 79.0 mC/cm2 at the first cycle and 97.9 mC/cm2 at the 12th cycle, suggesting the excellent reversibility of the investigated oxidative energy storage and conversion system.展开更多
The Potential step measurements are carried out on single beads of nickel hydroxide and the results are interpreted with a dual structure model featuring fast and slow diffusing components.The intrinsic diffusion coef...The Potential step measurements are carried out on single beads of nickel hydroxide and the results are interpreted with a dual structure model featuring fast and slow diffusing components.The intrinsic diffusion coefficients for the two components are found to be in the order of magnitude 10^(-7)and 10^(-13)~10^(-14)cm^(2)s^(-1),respectively,with an apparent value for the slow component in the order of 106^(-10)cm^(2)s^(-1).展开更多
The wide use of manganese dioxide(MnO_(2))as an electrode in all-solid-state asymmetric supercapacitors(ASCs)remains challenging because of its low electrical conductivity.This complication can be circumvented by intr...The wide use of manganese dioxide(MnO_(2))as an electrode in all-solid-state asymmetric supercapacitors(ASCs)remains challenging because of its low electrical conductivity.This complication can be circumvented by introducing trivalent gadolinium(Gd)ions into the MnO_(2).Herein,we describe the successful hydrothermal synthesis of crystalline Gd-doped MnO_(2) nanorods with Ni(OH)_(2) nanosheets as cathode,which we combined with Fe_(3)O_(4)/GO nanospheres as anode for all-solid-state ASCs.Electrochemical tests dem on strate that Gd dopi ng sign ifica ntly affected the electrochemical activities of the MnO_(2),which was further enhanced by introducing Ni(OH)_(2).The GdMnO_(2)/Ni(OH)_(2) electrode offers sufficient surface electrochemical activity and exhibits excellent specific capacity of 121.8 mA h g^(-1),at 1A g^(-1),appealing rate performance,and ultralong lifetime stability(99.3%retention after 10,000 discharge tests).Furthermore,the GdMnO_(2)/Ni(OH)_(2)//PVA/KOH//Fe_(3)O_(4)/GO solid-state ASC device offers an impressive specific energy density(60.25 W h kg^(-1))at a high power density(2332 W kg^(-1)).This investigation thus shows its large potential in developing novel approaches to energy storage devices.展开更多
Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was...Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni（OH）2 electrode performance are examined. The structure and property of the TiO2 added β-Ni（OH）2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni（OH）2 and TiO2 added β-Ni（OH）2 electrodes in 6 M KOH electrolyte. Anodic（Epa） and cathodic（Epc）peak potentials are found to decrease after the addition of TiO 2 into β-Ni（OH）2 electrode material. Further,addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni（OH）2 lectrode,TiO2 added β-Ni（OH）2 electrode is found to exhibit higher proton diffusion coefficient（D） and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni（OH）2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.展开更多
The recovery of nickel from spent nickel catalyst for the preparation of nickel hydroxide was studied. Nickel was extracted from the spent catalyst by acid leaching with 1 mol/L sulfuric acid at 90 ℃. Purified nickel...The recovery of nickel from spent nickel catalyst for the preparation of nickel hydroxide was studied. Nickel was extracted from the spent catalyst by acid leaching with 1 mol/L sulfuric acid at 90 ℃. Purified nickel solution was used in the preparation of nickel hydroxide. Three different methods, namely urea hydrolysis, conventional, and hydrothermal methods, of precipitation using NaOH were employed to get various nickel hydroxides samples named as Ni（OH）E-U, Ni（OH）2-C, and Ni（OH）E-H, respectively. Hydrothermal treatment induced better crystallinity in the Ni（OH）2 compared with conventional method. Both Ni（OH）2-C and Ni（OH）E-H samples have mixed phases of fl-Ni（OH）2 and a＊-Ni（OH）E.0.75H20 phases, whereas Ni（OH）2-U has only a＊-Ni（OH）2.0.75H20. TEM image of Ni（OH）E-U sample shows rod-like Ni（OH）2 structures. Among all, Ni（OH）2-U shows the best electrochemical activity.展开更多
The nickel hydroxide prepared by micro-emulsion method was doped by coprecipitated Zn. The effect of the amount of zinc-doped on the properties of Ni(OH)2 such as the reversibility of the electrode reaction, the charg...The nickel hydroxide prepared by micro-emulsion method was doped by coprecipitated Zn. The effect of the amount of zinc-doped on the properties of Ni(OH)2 such as the reversibility of the electrode reaction, the charge efficiency and active material utilization ratio of nickel electrode, and discharge specific capacity was studied by cyclic voltammetry and constant current charge-discharge tests. The results indicate that the specific discharge capacity of nickel hydroxide obtained by micro-emulsion method is much less than its theoretical value because the transfer of electrons and the diffusion of protons H+ are hindered owing to its crystal grain size in a nanometer range and thus possessing higher crystal interface resistance. The crystal cells are swelled and the crystal defects increased in prepared material due to part of Ni2+ substituted by Zn2+ when zinc and nickel hydroxide are coprecipitated. Hence, the electrons and protons H+ in the electrode reaction are transferred easily, the electrochemical behavior of nickel electrode is improved and discharge specific capacity is promoted. However, the performance of Ni(OH)2 is gradually enhanced with the addition of zinc-doped at first, while slowly decreased after the content of zinc is added to a certain value. The best electrode reaction reversibility, the highest electrode charge efficiency, the highest active material utilization ratio and the largest specific capacity on discharge are available when the mass fraction of Zn doped in nickel hydroxide by coprecipitation reaches 2.5 %.展开更多
Spherical Nano-scale nickel hydroxide was prepared through precipitation transmutation method by controlling the transmutation conditions in this paper. The measurement results of XRD and TEM indicate that the crystal...Spherical Nano-scale nickel hydroxide was prepared through precipitation transmutation method by controlling the transmutation conditions in this paper. The measurement results of XRD and TEM indicate that the crystallization of the nano-scale nickel hydroxide isβ-style and its shape is spherical with a diameter of 40～70 nanometer. The adulteration experiment shows that the adulteration ratio of nano- scale Ni(OH) 2 in common spherical micrometer-scale Ni(OH) 2 exists a optimal value (1∶9). And at this point, the utilization ratio of Ni(OH) 2 in electrodes can be raised by 10%, and the nano-scale nickel hydroxide with sphericity shape shows a better adulteration performance than that with needle shape.展开更多
The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effect...The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution （PSD） were investigated, d43 and PSD were measured online using a Malvern Insitec Liquid Pro- cess Sizer every 20 s. It was found that d43 varied between 13 kwh and 26 lain under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.展开更多
Nd-Al codoped amorphous nickel hydroxide powders were synthesized by microemulsion precipitation method combined with rapid freezing technique.The microstructure of the prepared samples was analyzed with X-ray diffrac...Nd-Al codoped amorphous nickel hydroxide powders were synthesized by microemulsion precipitation method combined with rapid freezing technique.The microstructure of the prepared samples was analyzed with X-ray diffractometer(XRD),scanning electron microscopy(SEM),and Raman spectroscopy.The electrochemical performances of the prepared samples were characterized with charge/discharge test,cyclic voltammetry,and electrochemical impedance spectra.The results showed that the codoping of Nd-Al resulted in more st...展开更多
Nickel hydroxide is widely used as cathode materials in nickel-metal secondary batteries.In this work,Mn-substituted nickel hydroxide samples with a special α/βmixed phase structure were synthesized by chemical co-p...Nickel hydroxide is widely used as cathode materials in nickel-metal secondary batteries.In this work,Mn-substituted nickel hydroxide samples with a special α/βmixed phase structure were synthesized by chemical co-precipitation method.The physical properties were char-acterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),differential scanning calorimetry(DSC)and field emission scanning electron microscopy(FE-SEM).The results show that the structure of the samples and the amount of intercalated anions and water molecules are highly related to the content of the Mn substituted.Their electrochemical performances were characterized by charge/discharge tests and electrochemi-cal cycle tests.The results demonstrate that the Mn-sub-stituted samples with a α/β mixed phase structure perform a much higher discharge capacity than normal β-nickel hydroxide.The specific discharge capacity reaches 330 mAh·g^(-1) after 50 cycles of charge/discharge in charging rate of 0.2C under ambient temperature.Mean-while,the samples show no capacity loss in electrochem-ical cycles,which indicates that the mixed phase nickel hydroxide maintains high structure stability.展开更多
The deactivation of nickel hydroxide to the electrooxidation of hypophosphite on anickel electrode was studied by means of in situ UV-Vis subtractive reflectance spectroscopy. Theexperimental results show that when th...The deactivation of nickel hydroxide to the electrooxidation of hypophosphite on anickel electrode was studied by means of in situ UV-Vis subtractive reflectance spectroscopy. Theexperimental results show that when the potential is lower than-1.0 V (SCE), the surfacc on nickelelectrode is free of nickel hydroxide, on which hypophosphite is active. When the potential movespositively to about-0.75V, two absorbency bands around 300 nm and 550 nm, which were ascribedto the formation of α-nickel hydroxide, were observed, nickel is oxidized to α-nickel hydroxide.Severe deactivation of the surface occurs when the nickel surface is covered with nickel hydroxide,which separates the hypophosphite ion from nickel substrate.展开更多
Nickel hydroxide doped with multi-wall carbon nanotubes(MCNTs)was synthesized by chemical coprecipitation method. The MCNTs doped nickel hydroxide was used as the electrochemical active material in the positive electr...Nickel hydroxide doped with multi-wall carbon nanotubes(MCNTs)was synthesized by chemical coprecipitation method. The MCNTs doped nickel hydroxide was used as the electrochemical active material in the positive electrodes of rechargeable alkaline batteries.The powder X-ray diffraction(XRD)analysis shows that the addition of MCNTs induces more structural defect within the crystal lattice of the nickel hydroxide.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS) tests demonstrate the better reaction reversibility and lower electrochemical impedance of MCNTs doped nickel hydroxide as compared with the pure nickel hydroxide.The charge/discharge tests show that MCNTs addition can improve the specific discharge capacity and increase the discharge voltage of the nickel hydroxide electrode.展开更多
The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scannin...The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scanning in 0.20 mol/L KOH. Similarly, GC/Co(OH) 2 electrode was prepared too. The experiments showed that the voltammetric behavior of GC/Ni(OH) 2 electrode in 0.20 mol/L KOH is more stable than that of GC/ Co(OH) 2. It was found that the GC/Ni(OH) 2 electrode acts as an effective electrocatalysis for the oxidation of hydrazine.展开更多
Nickel-metal hydride （Ni/MH） batteries are one of promising batteries for electric vehicle applications, but at high temperature the charge efficiency of nickel electrode is very low. In order to improve the high-te...Nickel-metal hydride （Ni/MH） batteries are one of promising batteries for electric vehicle applications, but at high temperature the charge efficiency of nickel electrode is very low. In order to improve the high-temperature-efficiency of nickel electrode, spherical nickel hydroxide mixed with various ratios of Lu2O3 was used as active material of pasted nickel electrodes. The results of charge/discharge experiments, cyclic voltammetric measurements and XRD characterizations have shown that after addition of Lu2O3, the oxygen evolution overpotcntial is elevated much, the charge efficiency of nickel electrode at high temperature is greatly improved and the content of β-NiOOH phase increases in charged electrodes. In addition, the mixed ratio of Lu2O3 has different effects on high temperature performances of nickel electrode at different charge/discharge currents, 3.5 % is the optimum mixed ratio, and the action of Lu2O3 on high temperature electrochemical behaviors is more apparent when nickel electrodes are charged at small current than large current.展开更多
Chemically precipitated β type nickel hydroxide powder was surface modified by electroless deposition of Co Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized ...Chemically precipitated β type nickel hydroxide powder was surface modified by electroless deposition of Co Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized by scanning electron microscopy (SEM), specific surface area (BET), X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). It has been found that Co and Zn components of the surface electroless coatings exist in the oxidized state. Electrochemical performances of pasted nickel electrodes using the modified nickel hydroxide as an active material were investigated, and compared with those of the electrodes prepared with the unmodified nickel hydroxide. Charge/discharge tests show that the modified nickel hydroxide electrodes exhibit better performances in the charge efficiency, specific discharge capacity and active material utilization. Their resistance to swelling with cycling is also superior to that of the unmodified nickel hydroxide electrodes. Cyclic voltammetric (CV) studies indicate that the modified electrodes have a higher electrochemical activity, and the porous pasted nickel electrodes have some distinguished CV characteristics in comparison with those of the thin film nickel electrodes.展开更多
Alpha nickel hydroxide has better performances than commercial beta nickel hydroxide. However, the main defect is that α-phase is difficult to synthesize and easily transformed to β-phase Ni（OH）2 upon aging in a s...Alpha nickel hydroxide has better performances than commercial beta nickel hydroxide. However, the main defect is that α-phase is difficult to synthesize and easily transformed to β-phase Ni（OH）2 upon aging in a strong alkaline solution. In this study, the Al-Co, Al-Yb, Yb-Co and Al-Yb-Co multiple doping was used respectively. By controlling the amount of sodium carbonate, the α-Ni（OH）2 was prepared by ultrasonic-assisted precipitation. And the influence of sodium carbonate on the crystalline phase and structure stability for alpha nickel hydroxide was studied. The results demonstrate that, with increasing amount, the biphase nickel hydroxide transforms to pure alpha nickel hydroxide gradually, and the structure stability is also improved. When the amount of sodium carbonate is 2 g, the sample still keeps α-Ni（OH）2 after being aged for 30 days, for Al-Yb-Co-Ni（OH）2. And when the amount is less than 2 g, the phase transformations exist in the samples with different extents. These results demonstrated that the amount of sodium carbonate is a critical factor to maintain the structural stability of α-Ni（OH）2.展开更多
基金National Natural Science Foundation of China(51704257,52174350)Hunan Provincial Science and Technology Innovation Program(2024AQ2039)。
文摘Fine nickel powders with a narrow particle size distribution were prepared by reducing nickel hydroxide in aqueous solution.The formation and reduction pathways of nickel powder were analyzed,as well as the effects of the molar ratio of hydrazine hydrate to nickel hydroxide,hydrazine concentration,and the dosage of surfactant PEG6000 on particle size,surface morphology,and dispersion.Results reveal that the nickel particle nucleation occurs on the nickel hydroxide surface,and the nickel hydroxide gradually dissolves during the reaction.With the increase in molar ratio of hydrazine hydrate to nickel hydroxide,the nickel particle size is initially decreased and then increased.Higher hydrazine hydrate concentrations result in smaller particle sizes.A small amount of PEG6000 surfactant can improve dispersion of nickel particles,but a higher amount of PEG6000 surfactant results in the maintenance of the morphology of nickel hydroxide.Adjusting the surfactant dosage can control the average particle size between 1-2μm.
基金Financial supports from the National Natural Science Foundation(No.21991104 and No.22,278,235)。
文摘Electrocatalysis has emerged as a sustainable approach for the selective oxidation of fatty alcohols to fatty acids,circumventing the environmental concerns associated with conventional routes.However,the low aqueous solubility of hydrophobic fatty alcohols presents a major challenge.While nickel hydroxide(Ni(OH)_(2))serves as a cost-effective catalyst for alcohol oxidation,its hydrophilic nature limits substrate accessibility and mass transport,causing sluggish kinetics and competing oxygen evolution.Herein,we propose a hydrophobic interface engineering strategy via co-electrodeposition of Ni(OH)_(2)with polytetrafluoroethylene(PTFE),fabricating the composite electrode(ED-Ni(OH)_(2)-PTFE).The optimized electrode achieves 95%Faradaic efficiency for octanoic acid at 1.5 V vs.RHE,with a production rate 2–3 times higher than pristine Ni(OH)_(2).Mechanistic studies combining in situ Raman spectroscopy,fluorescence imaging,and coarse-grained molecular dynamics simulations reveal that PTFE selectively enriches octanol at the electrode-electrolyte interface by modulating interfacial hydrophobicity.A continuous-flow microreactor integrating anodic octanol oxidation with cathodic hydrogen evolution reduces cell voltage by~100 m V,achieving simultaneous fatty acid and hydrogen production.This work highlights the critical role of hydrophobic interfacial microenvironment design in organic electrosynthesis,offering a promising strategy for upgrading fatty alcohols under mild conditions.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF),funded by the Ministry of Education(NRF-2018R1A6A1A03024962)the Ministry of Science and ICT(NRF-2020R1A2C2100746).
文摘Developing an efficient electrocatalyst for superior electrochemical water splitting(EWS)is crucial for achieving comprehensive hydrogen production.A heterostructured electrocatalyst,free of noble metals,Ti_(3)C_(2)MXene nanosheet-integrated cobalt-doped nickel hydroxide(NHCoMX)composite was synthesized via a hydrothermal method.The abundant pores in the Ti_(3)C_(2)MXene nanosheet(MX)-integrated microarchitecture increased the number of active sites and facilitated charge transfer,thus enhancing electrocatalysis.Specifically,the MXenhanced charge transfer considerably transformed the microelectronic structure of cobalt-doped Ni(OH)2(NHCo),which promoted its hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Hence,as an EWS catalyst,NHCoMX exhibited an exceptional electrocatalytic activity,demonstrating OER and HER overpotentials of 310 mV and 73 mV,respectively,with low Tafel slopes of 65 mV dec^(-1)and 85 mV dec^(-1),respectively;it exhibited a current density of 10 mV cm^(-2)in 1.0 mol L^(-1)KOH,representing the closest efficiency to the noble state-of-the-art RuO2 and Pt/C catalyst.Furthermore,the developed electrocatalyst improved the activities of both HER and OER,leading to an overall EWS current density of 10 mA cm^(-2)at 1.72 V in an alkaline electrolyte with two electrodes.This study describes an efficient heterostructured NHCoMX composite electrocatalyst.It is significantly comparable to the noble state-of-the-art electrocatalysts and can be extended to fabricate resourceful catalysts for large-scale EWS applications.
基金supported by the Research Funds of the State Key Laboratory for Marine Corrosion and Protection(No.JS220903).
文摘Carbon-based materials exhibit excellent dielectric absorption properties,among which graphene has received particular attention in research of electromagnetic wave absorbing materials because of its high electrical conductivity and unique large-area,thin-layer two-dimensional structural features.However,the electromagnetic absorption performance of the material is hindered from further improvement due to its single component composition.It is influenced by the conductive network of graphene,making it challenging to achieve a balance in impedance matching and electromagnetic loss,thereby restricting its broader application.To address these challenges,we developed a series of nickel hydroxide-modified graphene composites.Through a structural composite design,we optimized overall impedance matching,introduced diverse loss mechanisms to enhance electromagnetic loss performance,and utilized a secondary reaction control method to precisely regulate the deposition of nickel hydroxide on the graphene surface,thereby achieving regulate of the composite material's electromagnetic parameters within a defined range.Under low sample filling ratios and a thin sample thickness of 1.8 mm,the effective absorption bandwidth reaches 6.5 GHz,demonstrating excellent electromagnetic absorption performance.This study provides a controllable design approach for modulating material electromagnetic parameters by influencing the reaction process.It also offers a design method for composites with an outstanding electromagnetic loss mechanism.
基金Projects (50972128,51174176) supported by the National Natural Science Foundation of China
文摘The oxidative energy storage behaviors of a designed novel system comprising a nickel hydroxide film electrode and an oxygen-reducing platinum cathode were investigated by various electrochemical techniques. The structure and morphology of samples were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） analysis. It is found that the oxidative energy storage in the Ni（OH）2 electrodes can be obviously enhanced in the coupling system containing the cathode electrolytes with higher oxygen content or lower pH value. The results of the oxidation-discharge cycle tests show that the Ni（OH）2 film electrode oxidized in the coupling system with 1.0 mol/L Na2SO4 （pH=2） as cathode electrolyte for 600 s presents discharge capacities of 79.0 mC/cm2 at the first cycle and 97.9 mC/cm2 at the 12th cycle, suggesting the excellent reversibility of the investigated oxidative energy storage and conversion system.
基金supported by the National Natural Science Foundation of China(No.20073223)the State Key Laboratory for Physical Chemistry of Solid surfaces at Xiamen University(project No.200206)
文摘The Potential step measurements are carried out on single beads of nickel hydroxide and the results are interpreted with a dual structure model featuring fast and slow diffusing components.The intrinsic diffusion coefficients for the two components are found to be in the order of magnitude 10^(-7)and 10^(-13)~10^(-14)cm^(2)s^(-1),respectively,with an apparent value for the slow component in the order of 106^(-10)cm^(2)s^(-1).
基金the National Research Foundation of Korea(NRF),the Ministry of education,Korea(Project No.NRF2020R1F1A1061754)。
文摘The wide use of manganese dioxide(MnO_(2))as an electrode in all-solid-state asymmetric supercapacitors(ASCs)remains challenging because of its low electrical conductivity.This complication can be circumvented by introducing trivalent gadolinium(Gd)ions into the MnO_(2).Herein,we describe the successful hydrothermal synthesis of crystalline Gd-doped MnO_(2) nanorods with Ni(OH)_(2) nanosheets as cathode,which we combined with Fe_(3)O_(4)/GO nanospheres as anode for all-solid-state ASCs.Electrochemical tests dem on strate that Gd dopi ng sign ifica ntly affected the electrochemical activities of the MnO_(2),which was further enhanced by introducing Ni(OH)_(2).The GdMnO_(2)/Ni(OH)_(2) electrode offers sufficient surface electrochemical activity and exhibits excellent specific capacity of 121.8 mA h g^(-1),at 1A g^(-1),appealing rate performance,and ultralong lifetime stability(99.3%retention after 10,000 discharge tests).Furthermore,the GdMnO_(2)/Ni(OH)_(2)//PVA/KOH//Fe_(3)O_(4)/GO solid-state ASC device offers an impressive specific energy density(60.25 W h kg^(-1))at a high power density(2332 W kg^(-1)).This investigation thus shows its large potential in developing novel approaches to energy storage devices.
文摘Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni（OH）2 electrode performance are examined. The structure and property of the TiO2 added β-Ni（OH）2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni（OH）2 and TiO2 added β-Ni（OH）2 electrodes in 6 M KOH electrolyte. Anodic（Epa） and cathodic（Epc）peak potentials are found to decrease after the addition of TiO 2 into β-Ni（OH）2 electrode material. Further,addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni（OH）2 lectrode,TiO2 added β-Ni（OH）2 electrode is found to exhibit higher proton diffusion coefficient（D） and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni（OH）2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.
文摘The recovery of nickel from spent nickel catalyst for the preparation of nickel hydroxide was studied. Nickel was extracted from the spent catalyst by acid leaching with 1 mol/L sulfuric acid at 90 ℃. Purified nickel solution was used in the preparation of nickel hydroxide. Three different methods, namely urea hydrolysis, conventional, and hydrothermal methods, of precipitation using NaOH were employed to get various nickel hydroxides samples named as Ni（OH）E-U, Ni（OH）2-C, and Ni（OH）E-H, respectively. Hydrothermal treatment induced better crystallinity in the Ni（OH）2 compared with conventional method. Both Ni（OH）2-C and Ni（OH）E-H samples have mixed phases of fl-Ni（OH）2 and a＊-Ni（OH）E.0.75H20 phases, whereas Ni（OH）2-U has only a＊-Ni（OH）2.0.75H20. TEM image of Ni（OH）E-U sample shows rod-like Ni（OH）2 structures. Among all, Ni（OH）2-U shows the best electrochemical activity.
文摘The nickel hydroxide prepared by micro-emulsion method was doped by coprecipitated Zn. The effect of the amount of zinc-doped on the properties of Ni(OH)2 such as the reversibility of the electrode reaction, the charge efficiency and active material utilization ratio of nickel electrode, and discharge specific capacity was studied by cyclic voltammetry and constant current charge-discharge tests. The results indicate that the specific discharge capacity of nickel hydroxide obtained by micro-emulsion method is much less than its theoretical value because the transfer of electrons and the diffusion of protons H+ are hindered owing to its crystal grain size in a nanometer range and thus possessing higher crystal interface resistance. The crystal cells are swelled and the crystal defects increased in prepared material due to part of Ni2+ substituted by Zn2+ when zinc and nickel hydroxide are coprecipitated. Hence, the electrons and protons H+ in the electrode reaction are transferred easily, the electrochemical behavior of nickel electrode is improved and discharge specific capacity is promoted. However, the performance of Ni(OH)2 is gradually enhanced with the addition of zinc-doped at first, while slowly decreased after the content of zinc is added to a certain value. The best electrode reaction reversibility, the highest electrode charge efficiency, the highest active material utilization ratio and the largest specific capacity on discharge are available when the mass fraction of Zn doped in nickel hydroxide by coprecipitation reaches 2.5 %.
文摘Spherical Nano-scale nickel hydroxide was prepared through precipitation transmutation method by controlling the transmutation conditions in this paper. The measurement results of XRD and TEM indicate that the crystallization of the nano-scale nickel hydroxide isβ-style and its shape is spherical with a diameter of 40～70 nanometer. The adulteration experiment shows that the adulteration ratio of nano- scale Ni(OH) 2 in common spherical micrometer-scale Ni(OH) 2 exists a optimal value (1∶9). And at this point, the utilization ratio of Ni(OH) 2 in electrodes can be raised by 10%, and the nano-scale nickel hydroxide with sphericity shape shows a better adulteration performance than that with needle shape.
基金the State Key Development Program for Basic Research of China(2013CB632601)the National High Technology Research and Development Program of China(2011AA060704)+1 种基金the National Natural Science Foundation of China(21476236,91434126)the National Science Fund for Distinguished Young Scholars(21025627)
文摘The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution （PSD） were investigated, d43 and PSD were measured online using a Malvern Insitec Liquid Pro- cess Sizer every 20 s. It was found that d43 varied between 13 kwh and 26 lain under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.
基金supported by the National Natural Science Foundation of China (20563001)Guangxi Science Research and Technology Developing Foundation (05112001-2A1,0842003-12,0842003-15)Guangxi Natural Science Foundation (0991247)
文摘Nd-Al codoped amorphous nickel hydroxide powders were synthesized by microemulsion precipitation method combined with rapid freezing technique.The microstructure of the prepared samples was analyzed with X-ray diffractometer(XRD),scanning electron microscopy(SEM),and Raman spectroscopy.The electrochemical performances of the prepared samples were characterized with charge/discharge test,cyclic voltammetry,and electrochemical impedance spectra.The results showed that the codoping of Nd-Al resulted in more st...
基金financially supported by the National Natural Science Foundation of China (No.21403015)
文摘Nickel hydroxide is widely used as cathode materials in nickel-metal secondary batteries.In this work,Mn-substituted nickel hydroxide samples with a special α/βmixed phase structure were synthesized by chemical co-precipitation method.The physical properties were char-acterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),differential scanning calorimetry(DSC)and field emission scanning electron microscopy(FE-SEM).The results show that the structure of the samples and the amount of intercalated anions and water molecules are highly related to the content of the Mn substituted.Their electrochemical performances were characterized by charge/discharge tests and electrochemi-cal cycle tests.The results demonstrate that the Mn-sub-stituted samples with a α/β mixed phase structure perform a much higher discharge capacity than normal β-nickel hydroxide.The specific discharge capacity reaches 330 mAh·g^(-1) after 50 cycles of charge/discharge in charging rate of 0.2C under ambient temperature.Mean-while,the samples show no capacity loss in electrochem-ical cycles,which indicates that the mixed phase nickel hydroxide maintains high structure stability.
文摘The deactivation of nickel hydroxide to the electrooxidation of hypophosphite on anickel electrode was studied by means of in situ UV-Vis subtractive reflectance spectroscopy. Theexperimental results show that when the potential is lower than-1.0 V (SCE), the surfacc on nickelelectrode is free of nickel hydroxide, on which hypophosphite is active. When the potential movespositively to about-0.75V, two absorbency bands around 300 nm and 550 nm, which were ascribedto the formation of α-nickel hydroxide, were observed, nickel is oxidized to α-nickel hydroxide.Severe deactivation of the surface occurs when the nickel surface is covered with nickel hydroxide,which separates the hypophosphite ion from nickel substrate.
基金Project(20090450188)supported by China Postdoctoral Science FoundationProject supported by Postdoctoral Science Foundation of Central South University,ChinaProject(0991247)supported by Natural Science Foundation of Guangxi Province,China
文摘Nickel hydroxide doped with multi-wall carbon nanotubes(MCNTs)was synthesized by chemical coprecipitation method. The MCNTs doped nickel hydroxide was used as the electrochemical active material in the positive electrodes of rechargeable alkaline batteries.The powder X-ray diffraction(XRD)analysis shows that the addition of MCNTs induces more structural defect within the crystal lattice of the nickel hydroxide.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS) tests demonstrate the better reaction reversibility and lower electrochemical impedance of MCNTs doped nickel hydroxide as compared with the pure nickel hydroxide.The charge/discharge tests show that MCNTs addition can improve the specific discharge capacity and increase the discharge voltage of the nickel hydroxide electrode.
文摘The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scanning in 0.20 mol/L KOH. Similarly, GC/Co(OH) 2 electrode was prepared too. The experiments showed that the voltammetric behavior of GC/Ni(OH) 2 electrode in 0.20 mol/L KOH is more stable than that of GC/ Co(OH) 2. It was found that the GC/Ni(OH) 2 electrode acts as an effective electrocatalysis for the oxidation of hydrazine.
文摘Nickel-metal hydride （Ni/MH） batteries are one of promising batteries for electric vehicle applications, but at high temperature the charge efficiency of nickel electrode is very low. In order to improve the high-temperature-efficiency of nickel electrode, spherical nickel hydroxide mixed with various ratios of Lu2O3 was used as active material of pasted nickel electrodes. The results of charge/discharge experiments, cyclic voltammetric measurements and XRD characterizations have shown that after addition of Lu2O3, the oxygen evolution overpotcntial is elevated much, the charge efficiency of nickel electrode at high temperature is greatly improved and the content of β-NiOOH phase increases in charged electrodes. In addition, the mixed ratio of Lu2O3 has different effects on high temperature performances of nickel electrode at different charge/discharge currents, 3.5 % is the optimum mixed ratio, and the action of Lu2O3 on high temperature electrochemical behaviors is more apparent when nickel electrodes are charged at small current than large current.
文摘Chemically precipitated β type nickel hydroxide powder was surface modified by electroless deposition of Co Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized by scanning electron microscopy (SEM), specific surface area (BET), X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). It has been found that Co and Zn components of the surface electroless coatings exist in the oxidized state. Electrochemical performances of pasted nickel electrodes using the modified nickel hydroxide as an active material were investigated, and compared with those of the electrodes prepared with the unmodified nickel hydroxide. Charge/discharge tests show that the modified nickel hydroxide electrodes exhibit better performances in the charge efficiency, specific discharge capacity and active material utilization. Their resistance to swelling with cycling is also superior to that of the unmodified nickel hydroxide electrodes. Cyclic voltammetric (CV) studies indicate that the modified electrodes have a higher electrochemical activity, and the porous pasted nickel electrodes have some distinguished CV characteristics in comparison with those of the thin film nickel electrodes.
基金Funded by the National Natural Science Foundation of China(No.51604087)the Science and Technology Program of Guangdong Province of China(No.2016A010104019)the Science and Technology Program of Guangzhou City of China(No.201607010001)
文摘Alpha nickel hydroxide has better performances than commercial beta nickel hydroxide. However, the main defect is that α-phase is difficult to synthesize and easily transformed to β-phase Ni（OH）2 upon aging in a strong alkaline solution. In this study, the Al-Co, Al-Yb, Yb-Co and Al-Yb-Co multiple doping was used respectively. By controlling the amount of sodium carbonate, the α-Ni（OH）2 was prepared by ultrasonic-assisted precipitation. And the influence of sodium carbonate on the crystalline phase and structure stability for alpha nickel hydroxide was studied. The results demonstrate that, with increasing amount, the biphase nickel hydroxide transforms to pure alpha nickel hydroxide gradually, and the structure stability is also improved. When the amount of sodium carbonate is 2 g, the sample still keeps α-Ni（OH）2 after being aged for 30 days, for Al-Yb-Co-Ni（OH）2. And when the amount is less than 2 g, the phase transformations exist in the samples with different extents. These results demonstrated that the amount of sodium carbonate is a critical factor to maintain the structural stability of α-Ni（OH）2.
