Preparation And Hydrogen Evolution Performance Research Of Foamed Ni-Mo-Fe Alloy Electrode

Hydrogen energy is a kind of resourceful, renewable, storable and clean energy,so it is widely concerned all over the world. Electrolytic method is an important way toobtain hydrogen in industrial hydrogen production, but its cell voltage increases duringthe manufacturing process because of the existence of the cathodic overpotenial, thenenergy consumption increases. In order to reduce energy consumption, it’s ofmomentous significance to develop new and cheap cathode electrode materials whi chhave high catalytic activity. This thesis prepared the Ni-Mo-Fe alloy and Ni-Mo-Fe-Laelectrode material by electrodeposition and researched the electrochemical propertiesof hydrogen evolution reaction in30wt%KOH solution, explored the influence ofelectrodeposition process parameters on the the alloy hydrogen evolution andcharacterized every electrode by SEM, EDS and XRD.Ni-Mo-Fe electrode was prepared on foamed Ni by electro-deposition, and itsprimary experiment scheme was preliminarily determined by orthogonal experimentsand single factor experiments. The best electro-deposition conditionswere:Na3Cit2H2O120g·L-1, NiSO46H2O70g·L-1, Na2MoO42H2O25g·L-1,FeSO47H2O16g·L-1, C6H12O6H2O3g·L-1, C6H11NaO3g·L-1, C6H8O61g·L-1, C6H8O61g·L-1, C4H6O20.1g·L-1, NaCl10g·L-1, saccharin0.5g·L-1，C12H25NaO4S0.1g·L-1,NH3H2O100ml·L-1, current density40mA·cm-2, temperature40℃, time30min, andthe solution was stired in medium speed. The differences of hydrogen evolutionbehavior among foamed Ni, Ni-Mo and Ni-Mo-Fe alloy electrode were studied withthe application of Steady-state Polarization curve and A.C. impedance spectra in30%KOH solution, and it was found that under the current density of200mA·cm-2, theover-potential of Ni, Ni-Mo, Ni-Mo-Fe electrode in80℃,30%KOH solution wereseparately495mV,195mV,145mV, their Tafel slope b were separately0.093V,0.209V,0.166V and exchange current density i0were separately0.8×10-5A·cm-2,1.1×10-3A·cm-2,8.2×10-3A·cm-2, apparent activation energy is separately79.22kJ·mol-1,57.75kJ·mol-1,30.41kJ·mol-1. Tests showed that Ni-Mo-Fe alloy has the bestactivity of hydrogen evolution among the three electrodes. it was concluded that theirhydrogen evolution under the open circuit potential by analyzing their A.C. impedancespectrawas was mixed control process which includes electrochemical control anddiffusion control process. SEM and EDS results showed that the structure of Ni-Mocoating surface was cellular and the particles in the cellular structure is larger, the surface of electrode was very coarse. XRD results showed that the two kinds of alloywere crystalline structure, according to the Scherrer formula, the grain size ofNi-Mo coating is37.56nm and atom composition of the alloy was Ni82.1Mo17.9.Particles on Ni-Mo-Fe coating surface was more compact, and the grain size decreasedand small gaps appeared. The grain size of Ni-Mo-Fe coating is28.76nm and atomcomposition of the alloy was Ni70.1Mo20.2Fe9.7.Ni-Mo-Fe-La alloy electrode was prepared by adding LaCl37H2O into thesolution which was prepared for electrodepositing Ni-Mo-Fe electrode. The influencesof the concentration of LaCl37H2O, NiSO46H2O, Na2MoO42H2O, FeSO47H2O,stabilizers, the electrodeposition current density, and the electro-deposition time on thecatalytic activity of hydrogen evolution of the foamed Ni-Mo-Fe-La electrode werestudied. Finally, the best electro-deposition technological conditions were confirm asfollows: Na3Cit2H2O120g·L-1, NiSO46H2O70g·L-1, Na2MoO42H2O25g·L-1,FeSO47H2O16g·L-1, LaCl37H2O1g·L-1，C6H12O6H2O3g·L-1, C6H11NaO3g·L-1,C6H8O61g·L-1, C6H8O61g·L-1, C4H6O20.1g·L-1,NaCl10g·L-1, saccharin0.5g·L-1,C12H25NaO4S0.1g·L-1, NH3H2O100ml·L-1, current density40mA·cm-2,temperature40℃, time30mins, and the solution was stired in medium speed. Thehydrogen evolution behavior of Ni-Mo-Fe-La alloy electrode were studied with theapplication of Steady-state Polarization curve and A.C. impedance spectra in30%KOH solution, it was found that under the current density of200mA·cm-2, theover-potential of electrode in80℃,30%KOH solution was110mV, and its Tafel slopeb was0.105V, and exchange current density i0was5.9×10-2A·cm-2, apparent activationenergy is17.50kJ·mol-1. SEM and EDS results showed that the cellular structure onthe coating surface disappeared, and the size of the particles were smaller than that ofNi-Mo-Fe, and the surface was more smooth and compact, as well as, it was found thatthere were small micropores on the surface. XRD results showed that Ni-Mo-Fe-Laalloy was crystalline structure, according to the Scherrer formula, the grain size ofthe alloy coating is22.34nm and atom composition of the alloy wasNi66.9Mo25.6Fe6.2La1.3. So it can be concluded that the addition of La changed alloymicrostructure and coating surface morphology, refined the grain size, improved theplating smoothness and compactness, increased the coating superficial area andimproved the Mo content in the coating, which not only contributed to improvecatalytic activity of hydrogen evolution, but also increase the service life and stabilityof the electrode. Compared with foamed Ni electrode, Ni-Mo electrode, Ni-Mo-Feelectrode, foamed Ni-Mo-Fe-La electrode had the best catalytic activity of hydrogen evolution.