Ni-based Electrode Materials For Electrocatalytic Hydrogen Evolution Reaction

Hydrogen has been considered as an i deal and efficient fuel i n the future. Producing hydrogen by water electrolysis is the most promising route among many techniques for hydrogen production because of its numerous advantages, such as easy operating, low cost, pollution-free and so on. Efficient electrode materials for hydrogen evolutioin must possess these features such as good electrical conductivity, large active surface area, low hydrogen overpotential, good electrocatalytic activity, electrochemical stability and high corrosion resistance. However, because of the high energy consumption caused by the overpotential of hydrogen evolution reaction (HER), theirs application in industry on a large scale was restrained. Therefore, it is significant to fabricate electrode with lower overpotential on hydrogen evolution reaction. In this work, the electrodeposition technique was used to prepare electrode for electrocatalytic HER in weak acid electrolyte containing Yb2O3particulate or palygorskite powder and that in ammonia electrolyte containing suspending zeolite. And the electrochemical hydrogen evolution behavior of as prepared electrode was studied. Compared with the HER electrode prepared in acid solution, the electrode prepared in ammoniacal solution had a better performance for HER. The main reason was that ammonia and Ni2+could form complex, which could increase the cathodic polarization in electrodeposition process and inhibit the growth of the crystal nucleus speed, and then increase the specific surface area of the prepared electrodes and enhance the electrocatalytical performance for HER. By codeposition through adding4A-zeolite particle in ammoniacal solution, the Ni-zeolite composite electrode was fabricated. And due to the complexation and synergy effect between ammoniacal and zeolite, the electrode surface areas of the Ni-zeolite composite electrode could be further increased so that it could largely improve the electrode activity to achieve the complementary advantages of each component for hydrogen evolution reaction. The prepared Ni-zeolite composite electrode immersed in dilute hydrochloric acid and the zeolite was dissolved away to form the porous nickel based electrode. The diameter of cavern on the electrode surface was observed about300～400nm after zeolite particles were dissolved. It was shown that the real area was28times that of apparent area, and the apparent activation energy of HER on the porous nickel based electrode reduced22.12kJ mol-1. It was shown that hydrogen evolution potential of porous nickel based electrode moved positively about300mV at40mA cm-2compared with that of Niam electrode from steady-state polarization curves. These could be attributed to the formation of porous structure enhancing the real surface area of the electrode.The Ni-Yb2O3composite electrode was prepared by the codeposition technique. The crystalline Ni was successfully electrodeposited on Ti substrate and the Ni-Yb2O3composite electrode had rougher surface, which were indicated by XRD diffraction patterns and the SEM micrographs, separately. No doubt, this kind of structure was more advantageous for HER. The Ni-Yb2O3composite electrode had higher catalytic activity for HER, and the apparent exchange current density was32times that of pure Ni electrode based on the electrode reaction kinetic parameters. The apparent activation energy of reaction reduced20.08kJ mol-1. It was shown that hydrogen evolution potential of Ni-Yb2O3composite electrode moved positively about400mV at40mA cm-2compared with that of pure Ni electrode from steady-state polarization curves. The reasons were attributed to, on the one hand, the added Yb2O3particles improve the electrode real surface area, on the other hand, the synergy effect between Yb2O3particles and Ni reduced the activation energy for HER greatly.The Ni-palygorskite composite electrode was prepared by the codeposition technique. The crystalline Ni was successfully electrodeposited on Ti substrate and the surface morphology of nickel based electrode were changed by adding palygorskite, which were indicated by XRD diffraction patterns and the SEM micrographs, separately. No doubt, all these factors were more advantageous for HER. It was shown that hydrogen evolution potential of Ni-palygorskite composite electrode moved positively about300mV at40mA cm-2compared with that of pure Ni electrode from steady-state polarization curves. The exchange current density was3.03times that of pure Ni electrode which was calculated through hydrogen reaction kinetic parameters of i0, b, Rct gained from the Tafel polarization curve, and the electrode reaction apparent activation energy reduced12.42kJ mol-1. In conclusion, the added palygorskite improved the catalytic activity of Ni-based electrode for hydrogen evolution reaction. It was deduced that the synergy effect between palygorskite particles and Ni increased the surface area of the electrode and enhanced the catalytic activity of Ni-palygorskite composite electrode for hydrogen evolution reaction.