| Hydrogen has attracted more and more attention as an efficient and ideal clean energy.At present,electrolyzing water to make hydrogen is mainly used to obtain it.Therefore,the research and development of electrode materials with high hydrogen evolution activity has become an important means to reduce energy consumption in this method.Ni-Mo alloy have good hydrogen evolution activity in binary metal system,but its electrochemical activity still needs to be improved,and its corrosion resistance needs to be further improved.In this paper,a new type of nanocomposite coating was prepared by using pulse electrodeposition technique and unique properties of nano-materials.The Cr or Fe nano-particles were added into the Ni-Mo alloy plating bath respectively.It lays a foundation for the preparation of better hydrogen evolution materials and corrosion resistant materials.Firstly,Ni-Mo alloy coating was prepared,and the effects of duty cycle,temperature,current density and saccharin sodium additive on Ni-Mo alloy coating were analyzed.By virtue of scanning electron microscopy(SEM)and electrochemical measurement,better performance of Ni-Mo alloy coating were prepared by duty cycle 0.6,temperature 30℃,current density 2 A/dm~2 and no additive.In this basis,nano powder Cr or Fe is added in the bath to obtain Ni-W-Cr/Fe nanocomposite coating.By means of SEM,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and electrochemical measurement,the effects of the addition of nano-particles in solution and different process parameters on the surface morphology,structure,hydrogen evolution and corrosion resistance of the coating were studied.The morphology and properties of Ni-Mo,Ni-Mo-Cr and Ni-Mo-Fe coatings were compared.The results of SEM and EDS analysis showed that the content of Cr,Fe in the coating increased first and then decreased with the addition of Cr and Fe nano-particles increased in the bath.When the content of Cr,Fe particles was 20 g/L respectively,the content of Cr,Fe in the coating was the highest,which was 9.00wt.%and 26.48wt.%.However,the content of Mo in the coating decreased with the increased of nanoparticles in the bath.Compared with Ni-Mo alloy coating,Ni-Mo-Cr/Fe nanocomposite coating had refined grain,more dense and uniform coating and fewer cracks.The results of the electrochemical measurement showed that with the increase of the content of Cr and Fe particles in the coating,the hydrogen evolution overpotential of the polarization curve shifted positively.When the particle content of Cr and Fe were determined to be 20 g/L in the solution,respectively,the hydrogen evolution performance of Ni-Mo-Cr and Ni-Mo-Fe nanocomposite coatings were better.It was found that with deposition of Cr,Fe nano-particles in the coating,the impedance value of the coating decreases and the surface area increases.Therefore,addition of Cr and Fe nanoparticles could increased the hydrogen evolution performance of nanocomposite coating.Ni-Mo-Cr nanocomposite coating had better hydrogen evolution performance with comparison of Ni-Mo,Ni-Mo-Cr and Ni-Mo-Fe coatings.The results of corrosion resistance for coating shoued that with the addition of 20 g/L nano-particles into the bath,the corrosion resistance of the Ni-Mo coating can be improved by the positive shift of the self-corrosion potential and the decreasing of the self-corrosion current.Ni-Mo-Fe nanocomposite coating had better corrosion resistance,which is due to the addition of the same content of nanoparticles to the bath,but the content of the nano-particles deposited on the coating was different.The content of nano Fe particles in Ni-Mo-Fe coating(26.48wt.%)was higher than that in Ni-Mo-Cr coating(9.00wt.%).Nano-particles can distribute evenly in the coating,reduce the contact area between the corrosion medium and the base metal,and improve the corrosion resistance.Therefore,the corrosion resistance of Ni-Mo-Fe nanocomposite coating is better under the above conditions. |
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