| With consumption of petrochemical fuel increased and reserves resources decreased gradually,the development of green renewable energy will be resolved.Hydrogen is a kind of clean renewable energy and will be widely concerned by people.The main source of hydrogen energy is electrolyzed water.But this technology need to consume more and more power and high cost of production.Large power consumption is used because that the electrolytic electrode over-potential is very high.The new nanocomposite coating will be prepared by the pulsed electrodeposition technique in this paper.After taking use of the unique property of nanomaterial,the new pulsed nanocomposite coating can be used as hydrogen evolution material which reduce energy consumption.It's a important role that the new nanocomposite coating improve on the energy shortage.Electrodeposition process parameters were that stirring speed was 100r/min,pulse frequency was 200 Hz,pulse duty cycle was 0.4,average current density was 3A/dm2,pH in solution was 5.6,plating time was 60 minute and plating temperature was 25 ?.With different addition of nano-powder of W,Cr in solution,the surface morphologies and structures of nanocomposite coating were investigated by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The hydrogen evolution behavior of the coating was studied by electrochemical method of measurement and thermal shock experiment.On the basis of this,we compared with the hydrogen evolution of Ni,Ni-5W,Ni-5Cr and Ni-5W-5Cr nanocomposite coatings.We also discussed the mechanism of hydrogen evolution of nanocomposite coatings.At the same time,the high temperature oxidation behavior of the coating was studied at 24 hours and 800 ? temperature.The results of SEM and XRD analysis showed that with the addition of W and Cr nanopowders increased in the bath,it's reduced phenomenon of irregular clusters that Ni grain contains nanopowder of W and Cr.It could improve on the dispersibility of the nanocomposite coating and decrease Ni grain size of the nanocomposite coating.So it became the dense and uniform coating.The thermal shock test results showed that heightened with the amount of W nanometer powder in the bath,the binding force of the coating was increased.The results of the electrochemical cathodic polarization curves showed that the content of W and Cr in the bath can change the hydrogen evolution potential of the coating.The electrochemical cathodic polarization curve showed that Ni-50 W nanocomposite coating's hydrogen evolution over-potential was shifted by 360 m V over Ni-5W nanocomposite coating's.Hydrogen evolution over-potential of Ni-20 Cr nanocomposite coating was moved 300 mV forward Ni-5Cr nanocomposite coating's.When the content of W nano-powder was 50g/L and the content of Cr nano-powder was 20g/L in the bath,respectively,the hydrogen-evolution activities of Ni-W and Ni-Cr nanocomposite coatings were better.The hydrogen evolution over-potential of Ni-5W-5Cr nanocomposite coating was-1.2V,which was shifted by 250 mV over Ni coating and was shifted by 200 mV over Ni-Cr nanocomposite coatings and was shifted by 150 mV over Ni-W nanocomposite coating,respectively.The exchange impedance spectrum available showed that the addition of W and Cr nanoparticles increased the coverage of H atoms in coating.The impedance value of Ni-W-Cr nanocomposite coating was reduced.Addition of W and Cr nanoparticles increased the surface area of the nanocomposite coating and the hydrogen evolution performance.The mechanism of hydrogen evolution was controlled by the process of electrochemical polarization.The control step of hydrogen evolution was electrochemical desorption process.After adding W and Cr particles in the bath,W and Cr particles enhanced the adsorption capacity of hydrogen atoms.Desorption rate and the amount of hydrogen evolution were risen.The results showed that the nanoparticles of W and Cr in the coating could not improve the high temperature oxidation of Ni-W-Cr nanocomposite coatings because it was lower content nanoparticles which only played a doping effect. |
PDF Full Text Request