Metal-organic framework-derived Ni doped Co_(3)S_(4) hierarchical nanosheets as a monolithic electrocatalyst for highly efficient hydrogen evolution reaction in alkaline solution

Hierarchical nanostructure construction and electronic structure engineering are commonly employed to increase the electrocatalytic activity of HER electrocatalysts.Herein,Ni doped Co_(3)S_(4) hierarchical nanosheets on Ti mesh(Ni doped Co_(3)S_(4) HNS/TM)were successfully prepared by using metal organic framework(MOF)as precursor which was synthesized under ambient condition.Characterization results confirmed this structure and Ni incorporation into Co_(3)S_(4) lattice as well as the modified electronic structure of Co_(3)S_(4) by Ni doping.Alkaline HER performance showed that Ni doped Co_(3)S_(4) HNS/TM presented outstanding HER activity with 173 m V overpotential at-10 m A·cm^(-2),surpassing most of metal sulfide-based electrocatalysts.The hierarchical structure,superior electrical conductivity and electronic structure modulation contributed to the accelerated water dissociation and enhanced intrinsic activity.This work provides a new avenue for synthesizing hierarchical nanostructure and simultaneously tuning the electronic structure to promote HER performance,which has potential application in designing highly efficient and cost-effective HER nanostructured electrocatalyst.

Electrochemical synthesis of Ni doped carbon quantum dots for simultaneous fluorometric determination of Fe^(3+)and Cu^(2+)ion facilely

A novel Ni doped carbon quantum dots(Ni-CQDs)fluorescence probe was synthesized by facile electrolysis of monoatomic Ni dispersed porous carbon(Ni–N–C).The obtained Ni-CQDs showed a high quantum yield of 6.3%with the strongest excitation and emission peaks of 360 nm and 460 nm,and maintained over 90%of the maximum fluorescence intensity in a wide p H range of 3–12.The metal ions detectability of Ni-CQDs was enhanced by Ni doping and functional groups modification,and the rapid and selective detection of Fe^(3+)and Cu^(2+)ions was achieved with Ni-CQDs through dynamic and static quenching mechanism,respectively.On one hand,the energy band gap of Ni-CQDs was regulated by Ni doping,so that excited electrons in Ni-CQDs were able to transfer to Fe^(3+)easily.On the other hand,the abundant functional groups promoted the generation of static quenching complexation between Cu^(2+)and Ni-CQDs.In metal ions detection,the linear quantitation range of Fe^(3+)and Cu^(2+)were 100–1000μM(R^(2)=0.9955)and 300–900μM(R^(2)=0.9978),respectively.The limits of detection(LOD)were calculated as 10.17 and 7.88μM,respectively.Moreover,the fluorescence quenched by Cu^(2+)could be recovered by EDTA2-due to the destruction of the static quenching complexation.In this way,NiCQDs showed the ability to identify the two metal ions to a certain degree under the condition of Fe^(3+)and Cu^(2+)coexistent.This work paves the way of facile multiple metal ion detection with high sensitivity.

Efficient splitting of alcohols into hydrogen and C–C coupled products over ultrathin Ni‐doped ZnIn_(2)S_(4) nanosheet photocatalyst

Integrating selective organic synthesis with hydrogen(H_(2))evolution in one photocatalytic redox reaction system sheds light on the underlying approach for concurrent employment of photogenerated electrons and holes towards efficient production of solar fuels and chemicals.In this work,a facile one‐pot oil bath method has been proposed to fabricate a noble metal‐free ultrathin Ni‐doped ZnIn_(2)S_(4)(ZIS/Ni)composite nanosheet for effective solar‐driven selective dehydrocoupling of benzyl alcohol into value‐added C–C coupled hydrobenzoin and H_(2) fuel,which exhibits higher performance than pure ZIS nanosheet.The remarkably improved photoredox activity of ZIS/Ni is mainly attributed to the optimized electron structure featuring narrower band gap and suitable energy band position,which facilitates the ability of light harvesting and photoexcited charge carrier separation and transfer.Furthermore,it has been demonstrated that it is feasible to employ ZIS/Ni for various aromatic alcohols dehydrocoupling to the corresponding C–C coupled products.It is expected that this work can stimulate further interest on the establishment of innovative photocatalytic redox platform coupling clean solar fuels synthesis and selective organic conversion in a sustainable manner.

Modulating the CO methanation activity of Ni catalyst by nitrogen doped carbon

Nitrogen doping has been proved to be an effective way to modify the properties of graphene and other carbon materials. Herein, we explore a composite with nitrogen doped carbon overlayers wrapping Si C substrate as a support for Ni（Ni/CN-Si C） and evaluate its effects on the methanation activity. The results show that both the activity and stability of Ni are enhanced. Characterization with STEM, XRD, XPS, Raman and H2-TPR indicates that nitrogen doping generates more defects in the carbon overlayers, which benefit the dispersion of Ni. Furthermore, the reduction of Ni is facilitated.

Nickel Antimony Sulphide Thin Films for Solar Cell Application: Study of Optical Constants

Chemical bath deposition technique has been used to deposit Ni-doped Sb2S3 thin films onto glass substrate. Doping was carried out by adding 1, 3 and 5 wt% of Ni. Bath temperature was kept as 10℃ and films were annealed at 250℃ under vacuum. Polycrystalline nature of films with an orthorhombic phase was analyzed by X-ray diffraction technique. Scanning electron microscopy was used for morphological study which shows that grains are spherical. Optical measurements using transmittance data indicated that films have a direct band gap of 1.00 - 2.60 eV with an absorption coefficient of ~104 cm-1 in visible range. The average value of electrical conductivity was calculated as 1.66, 1.11 and 1.06 (Ω·cm)-1 for as-deposited films and 1.90, 2.08 and 1.15 (Ω·cm)-1 for annealed films while refractive indices were found as 2.18 - 3.38 and 1.91 - 3.74 respectively. The obtained films can be used for solar cell applications due to their good absorbing properties like higher absorption coefficient and refractive index values.

Effects of Ni doping contents on photocatalytic activity of B-BiVO_4 synthesized through sol-gel and impregnation two-step method

To enhance the photocatalytic activity of B-BiVO4,Ni-doped B?BiVO4photocatalyst(Ni-B-BiVO4)was synthesized through sol-gel and impregnation method.The photocatalysts were characterized by XPS,XRD,SEM,EDS,BET and UV-Vis DRS techniques.The results showed that single or double doping did not change the crystalline structure and morphology,but the particle size decreased with Ni doping.The band gap energy absorption edge of Ni-B-BiVO4shifted to a longer wavelength compared with undoped,B or Ni single doped BiVO4.More V4+and surface hydroxyl oxygen were observed in BiVO4after Ni-B co-doping.When the optimal mass fraction of Ni is0.30%,the degradation rate of MO in50min is95%for0.3Ni-B-BiVO4sample which also can effectively degrade methyl blue(MB),acid orange(AOII)II and rhodamine B(RhB).The enhanced photocatalytic activity is attributed to the synergistic effects of B and Ni doping.

Effect of Ni-doping on electrochemical capacitance of MnO_2 electrode materials

Mn/Ni composite oxides as active electrode materials for supercapacitors were prepared by solid-state reaction through the reduction of KMnO4 with manganese acetate and nickel acetate at low temperature. The products were characterized by X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The electrochemical characterizations were performed by cyclic voltammetry (CV) and constant current charge-discharge in a three-electrode system. The effects of different potential windows, scan rates, and cycle numbers on the capacitance behavior of Mn0.8Ni0.2Ox composite oxide were also investigated. The results show that the composite oxides are of nano-size and amorphous structure. With increasing the molar ratio of Ni, the specific capacitance goes through a maximum at molar fraction of Ni of 20%. The specific capacitance of Mn0.8Ni0.2Ox composite oxide is 194.5 F/g at constant current discharge of 5 mA.

Ni doping effects in YBa_2Fe_3O_(8+w)

By doping Ni into YBa2Fe308＋w （YBFO） system, we obtained the phase YBa2Fe3-xNixO8＋w （YBFNO, x=0, 0.05, 0.10, 0.15, 0.30, 0.50, 1.00）. This paper discusses the changes in crystal structural, resistivity and magnetoresistivity （MR） of YBFO samples due to the incorporation of transition metal Ni. The results show that Ni substitution for partial Fe in YBFO does not substantially transform the structure of parent phase, but results in tiny changes in the lat- tice parameters. The YBFO crystal with Ni doped is semiconducting.

Electrochemically exfoliated Ni-doped MoS_(2) nanosheets for highly efficient hydrogen evolution and Zn-H_(2)O battery

Thanks to tunable physical and chemical properties,two-dimensional(2D)materials have received intensive interest,endowing their excellent electrocatalytic performances for applications in energy conversion.However,their catalytic activities are largely determined by poor adsorption energy and limited active edge sites.Herein,a one-step electrochemical exfoliation strategy was developed to fabricate 2D Ni-doped MoS_(2)nanosheets(Ni-EX-MoS_(2))with a lateral size of500 nm and thickness of3.5 nm.Profiting from high electrical conductivity and abundant exposing active sites,Ni-EX-MoS_(2)catalyst displayed an admirable performance for electrochemical hydrogen evolution reaction(HER)with a low overpotential of 145 m V at 10 m A/cm^(2)as well as a small Tafel slope of 89 m V/dec in alkaline media,which are superior to those of the most reported MoS_(2)-based electrocatalysts.The formed Ni species with tuning electronic structure played a crucial role as primary active center of Ni-EX-MoS_(2),as well as the forming stable 1T/2H phase MoS_(2)interface demonstrated a synergistic effect on electrocatalytic HER performance.Further,Ni-EX-MoS_(2)was employed as a cathode electrode for alkaline Zn-H_(2)O battery,which displayed a high power density of 3.3 m W/cm^(2)with excellent stability.This work will provide a simple and effective guideline for design of electrochemically exfoliated transition metal-doped MoS_(2)nanosheets to inspire their practical applications in energy catalytic and storage.

Nickel-modified In_(2)O_(3) with inherent oxygen vacancies for CO_(2) hydrogenation to methanol

Methanol synthesis is one of the most important industrially-viable approaches for carbon dioxide(CO_(2)) utilization, as the produced methanol can be used as a platform chemical for manufacturing green fuels and chemicals. The In_(2)O_(3) catalysts are ideal for sustainable methanol synthesis and have received considerable attention. Herein, Co-, Ni-and Cu-modified In_(2)O_(3) catalysts were fabricated with high dispersion and high stability to improve the hydrogenation performance. The Ni-promoted In_(2)O_(3) catalyst in the form of high dispersion possessed the largest amount of oxygen vacancies and the strongest ability for H_(2) activation, leading to the highest CO_(2) conversion and space time yield of methanol of 0.390 g_(Me OH)g_(cat)^(-1)h^(-1) with CH_(3)OH selectivity of 68.7%. In addition, the catalyst exhibits very stable performance over 120 h on stream, which suggests the promising prospect for industrial applications. Further experimental and theoretical studies demonstrate that surface Ni doping promotes the formation of oxygen defects on the In_(2)O_(3) catalyst, although it also results in lower methanol selectivity. Surprisingly, subsurface Ni dopants are found to be more beneficial for methanol formation than surface Ni dopants, so the Nipromoted In_(2)O_(3)catalyst with a lower surface Ni content at the similar Ni loading can reach higher methanol selectivity and productivity. This work thus provides theoretical guidance for significantly improving the CO_(2) reactivity of In_(2)O_(3)-based catalysts while maintaining high methanol selectivity.

Iron isotopic analyses of geological reference materials on MC-ICP-MS with instrumental mass bias corrected by three independent methods

Here we report iron(Fe) isotopic data of three pure Fe solution standards(IRMM-014, GSB Fe, and NIST3126a) and five widely used geological reference materials(RMs) from the United States Geological Survey and Geological Survey of Japan obtained on a Neptune Plus multi-collector–inductively coupled plasma–mass spectrometer(MC-ICP-MS) in our laboratory over the past 3 years. The instrumental mass bias was corrected by three independent methods: sample-standard bracketing(SSB),Ni doping + SSB, and ^(57)Fe–^(58)Fe double spike + SSB.Measurements reveal that both the Ni doping and double spike methods helped calibrate short-term fluctuations in mass bias. Collectively, almost all measurements of RMs yielded δ^(56)Fe within ± 0.05 of recommended values,provided that each sample was measured four times on MC-ICP-MS. For the first time, new recommended values for NIST SRM3126a are reported(δ^(56)Fe = 0.363 ± 0.006,2SE, 95% CI; and δ^(57)Fe = 0.534 ± 0.010, 2SE).

Experimental and DFT studies of flower-like Ni-doped Mo_(2)C on carbon fiber paper:A highly efficient and robust HER electrocatalyst modulated by Ni(NO_(3))_(2)concentration

Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required.In this work,we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo_(2)C on carbon fiber paper(Ni–Mo_(2)CCB/CFP)for hydrogen evolution reaction(HER).The effects of nickel nitrate concentration on the phase composition,morphology,and electrocatalytic HER performance of Ni-doped Mo_(2)C@CFP electrocatalysts was investigated.With the continuous increase of Ni(NO_(3))_(2)concentration,the morphology of Mo_(2)C gradually changes from granular to flower-like,providing larger specific surface area and more active sites.Doping nickel(Ni)into the crystal lattice of Mo_(2)C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity.The as-developed Mo_(2)C–3 M Ni(NO_(3))_(2)/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm^(-2).This catalyst has a fast HER kinetics,as demonstrated by a very small Tafel slope of 27.4 mV·dec^(-1),and persistent long-term stability.A further higher Ni concentration had an adverse effect on the electrocatalytic performance.Density functional theory(DFT)calculations further verified the experimental results.Ni doping could reduce the binding energy of Mo–H,facilitating the desorption of the adsorbed hydrogen(Hads)on the surface,thereby improving the intrinsic catalytic activity of Ni-doped Mo_(2)C-based catalysts.Nevertheless,excessive Ni doping would inhibit the catalytic activity of the electrocatalysts.This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity,but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.

Facile synthesis of Ni-doped SnO_(2) nanorods and their high gas sensitivity to isopropanol

In this work,pure SnO_(2) and Ni-doped SnO_(2) nanorods were synthesized through a one-step template-free hydrothermal method and then used to detect isopropanol.Sensors fabricated with the Ni-doped SnO_(2) nanocomposites showed the best gas sensing performance when the Ni doping amount was 1.5 mol.%.The response reached 250 at 225℃,which was approximately 8.3 times higher than that of the pure SnO_(2) nanorods.The limit of detection for isopropanol was as low as 10 ppb at the optimum working temperature.In addition,it also displayed good selectivity and excellent reproducibility.It is believed that the enhanced isopropanol sensing behavior benefit from the increased oxygen defects and larger specific surface area by Ni doping.

Rational design of efficient visible-light photocatalysts(1D@2D/0D)ZnO@Ni-doped BiOBr/Bi heterojunction:Considerations on hierarchical structures,doping and SPR effect

Simultaneously integrating heterogeneous interface,element doping,and metal decorating was a promising strategy to promote the visible-light-driven photocatalytic activity.Herein,we demonstrated a facile solvothermal route for Ni-doped BiOBr/Bi^(0) with ZnO 3D hierarchical heterojunction(denoted as Z@B/BiNi).The optimal photocatalysts of Z@B/Bi-Ni sample presented a remarkable catalytic performance of high concentrations of tetracycline solution(40 mg/L)than those of the Z@B/Bi,Z@B,BOB and ZnO photocatalysts toward the visible-light-driven degradation.The enhanced photocatalytic mechanism can be proposed as follows:(ⅰ)3D hierarchical heterojunction provided more active sites and accelerated the separation of charge carriers for photocatalytic TC;(ⅱ)formation of oxygen vacancies on the surface over Z@B/Bi-Ni by in-situ reduction of Bi^(0) and Ni doping could serve as the active sites for oxygen activation to adsorb free O_(2) and generate more superoxide radicals;(ⅲ)SPR effect of Bi metal were beneficial to carrier separation and also act as the active site to trap O_(2) molecules.This work clarified the role of unique morphologies,surface plasmonic resonance(SPR)effect of metal Bi,and Ni doping in Z@B/Bi-Ni,and its photocatalytic reaction mechanism was proposed by a series of experiments,characterization and DFT calculations,arousing a new perspective to design hierarchical heterojunction photocatalysts.

Hollow hydrangea-like nitrogen-doped NiO/Ni/carbon composites as lightweight and highly efficient electromagnetic wave absorbers

Hierarchical hollow-structured magnetic–dielectric materials are considered to be promising and competitive functional absorbers for microwave absorption(MA).Herein,a hierarchical hollow hydrangea multicomponent metal oxides/metal-carbon was designed and successfully produced via a facile self-assembly method and calcination process.Adequate magnetic NiO and Ni nanoparticles were suspended within the hollow hydrangea-like nitrogen-doped carbon matrix(HH N-NiO/Ni/C),constructing a unique hierarchical hollow structured multicomponent magnetic–dielectric MA composite.The annealing temperature and oxidation time were carefully regulated to investigate the complex permittivity and permeability.HH N-NiO/Ni/C delivers exceptional MA properties with maximum reflection loss of–45.8 dB at 1.7 mm thickness and displays a wide effective absorption frequency range of 5.6 GHz.The superior MA performance can be attributed to the following aspects:(1)The hierarchical hollow multicomponent structure offers plentiful of heterojunction interfaces triggering interfacial polarization;(2)nitrogen doped-carbon(N-C)facilitates the conductive loss by the unique electron migration path in the graphitized C and NiO/Ni;(3)magnetic NiO/Ni nanoparticles homogeneously dispersed within N-C form extensive C skeleton and strengthen the magnetic response ability;(4)hierarchical hollow wrinkled structures possess a large interspace and heterogeneous interface improving polarization loss and enhancing multireflection process and the unique structure satisfies magnetic and dielectric loss simultaneously resulting from synergistic effects of different components within the composites.

Tailoring activation sites of metastable distorted 1T′-phase MoS_(2) by Ni doping for enhanced hydrogen evolution

Heteroatom doping is a promising approach to enhance catalytic activity by modulating physical properties,electronic structure,and reaction pathway.Herein,we demonstrate that appropriate Ni-doping could trigger a preferential transition of the basal plane from 2H(trigonal prismatic)to 1T′(clustered Mo)by inducing lattice distortion and S vacancy(SV)and thus dramatically facilitate its catalytic hydrogen evolution activity.It is noteworthy that the unique catalysts did possess superior catalytic performance of hydrogen evolution reaction(HER).The rate of photocatalytic hydrogen evolution could reach 20.45 mmol·g^(−1)·h^(−1) and reduced only slightly in the long period of the photocatalytic process.First-principles calculations reveal that the distorted Ni-1T′-MoS_(2) with SV could generate favorable water adsorption energy(Ead(H_(2)O))and Gibbs free energy of hydrogen adsorption(∆GH).This work exhibits a facile and promising pathway for synergistically regulating physical properties,electronic structure,or wettability based on the doping strategy for designing HER electrocatalysts.

Ni–Al composite hydroxides fabricated by cation–anion double hydrolysis method for high-performance supercapacitor

Chemical doping of nickel hydroxide with other cations（e.g. Al^（3＋）） is an efficient way to enhance its electrochemical capacitive performances. Herein, a simple cation–anion（Ni^（2＋）and AlO_2） double hydrolysis method was developed toward the synthesis of nickel–aluminum（Ni–Al） composite hydroxides. The obtained composite hydroxides possesses a porous structure, large surface area（121 m^2/g） and homogeneous element distribution. The electrochemical test shows that the obtained composite hydroxides exhibits a superior supercapacitive performances（specific capacitance of 1670F/g and rate capability of 87% from 0.5 A/g to 20 A/g） to doping-free nickel hydroxide（specific capacitance of 1227 F/g and rate capability of 47% from 0.5 A/g to 20 A/g）. Moreover, the galvanostatic charge/discharge test displays that after 2000 cycles at large current density of 10 A/g, the composite hydroxides achieves a high capacitance retention of 98%, indicative of an excellent electrochemical cycleability.

Alloying engineering for thermoelectric performance enhancement in p-type skutterudites with synergistic carrier concentration optimization and thermal conductivity reduction

The enhancements in thermoelectric(TE)performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more impurity phases induced by inherent structural instability of a Fe-based skutterudite.As shown in this study,alloying engineering of Ni doping at Fe sites in a p-type CeFe_(3.8)Co_(0.2)Sb_(12)skutterudite can not only reduce the impurity phases with high thermal conductivity but also regulate the carrier concentration,and thus significantly increase the Seebeck coefficient.The thermal conductivity was largely suppressed due to the enhanced point defect phonon scattering and decreased hole concentration.As a result,a TE figure of merit ZT of the CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)sample reached 0.8,which is approximately 50%higher than that of a Ni-free sample.Appropriate Ni doping can maintain a high ZT at a high temperature by controlling the reduction in a band gap.Therefore,a high average ZT close to 0.8 at 650–800 K for CeFe_(3.5)Ni_(0.3)Co_(0.2)Sb_(12)was obtained,which was comparable to or even higher than those of the reported Ce-filled Fe-based skutterudites due to the synergistic optimization of electrical and thermal performances.This study provides a strategy to synergistically optimize electrical–thermal performances of the p-type skutterudites by alloying engineering.