engleski

Electrolytic hydrogen evolution kinetics: Relation to the electronic properties of the Zr-Ni metallic glasses

Experimental results of the hydrogen evolution kinetics (the h.e.r.) on amorphous Zr_100-x Ni_x alloys (x between 24 and 60), obtained from a.c. and d.c. in situ measurements in 1 M NaOH solution, were related (discussed) to the split-band electronic structure of the Ni-Zr system. Our results show that the key to understanding electrocatalytic properties of Zr – Ni amorphous alloys for the h.e.r. is the electronic structure. For the Ni rich alloys with c less and equal to 60 due to the widening of the Ni d band, the Ni contribution to the electronic density of state at the Fermi level n(E_F) becomes predominant and a large enhancement of the catalytic activity is observed. For concentration higher than 70 percent Ni this contribution increases rapidly and the highest catalytic activity could be expected. The process of desorption takes place easier and faster, in accordance with the finding that 3d bonds of nickel atoms tend to have a weaker interaction with hydrogen compared to the zirconium atoms. As far as the electrochemical desorption is the rate-determining step of the h.e.r., a M-H interaction may also be taken in account in specifying the site for the h.e.r. For Zr rich Zr_100-x Ni_x (x = 33,24), n(E_F) is mainly related to the Zr 4d states, the Ni contribution being small. Such a structure is favorable for bonding with either oxygen or hydrogen resulting in the lowering electrocatalytic activity for the hydrogen evolution reaction.

Zr-Ni amorphous alloys, electrocatalysis, hydrogen evolution, electronic structure, oxide-hydride formation

nije evidentirano