Preparation of Amorphous Ti-Ni Films and Study on the Electrocatalytic Properties
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M+H20+e- --hargeMH1fl.dIOll discharge
(2)
MH.d
charge
•
•.
discharge
It can be seen in reaction I and 2 that
the
hydrogen
715 Mat. Res. Soc. Symp. Proc. Vol. 318.
1994 Materials Research Society
is
the
first
generated and adsorbed at the cathode surface, then diffused into the lattic positions of the alloy phase forming the metallic hydride in the charge process. So it is clear that the surface electrocatalytic properties of the hydride electrode play an important role during overall electrode reactions. In bulk alloys, however, the electrocatalysurface reaction is not correctly characterized tic activity of because both the surface reaction (reaction 1) and the hydride-forming reaction (reaction 2) overlap each other during electrode reactions. In order to reduce the complexity of investigating the hydride electrode reactions and stress the electrochemical surface reaction, we developed the film-electrode of Ti-Ni hydrogen storage alloy and the amorphous Ti-Ni alloy films were prepared by ion beam sputtering technique. The surface charateristics and electrocatalytic properties of the filmelectrode in alkaline solution were investigated.
EXPERIMENTAL Preparation and characterization of the thin films The amorphous Ti- Ni films were prepared by means of ion beam sputtering using TiNi and Ti.Ni alloy targets. The sputtering system was described in the previous paper[7]. The nickel foil ( 0.11mm thick and 99.8% pure) was used as the substrate after polished mechanically Prior to the sputtering and degreased with alkaline solution. deposition, the alloy target was presputtered for 10-20 minutes. During the sputter, the ion beam voltage and current were 3.3KV and IIWmA, respectively, the pressure in vacuum chamber was 9.3Xl0-aPa. The chemical composition of the film deposited on Si substrate was measured by Rutherford backscattering spectrometry. The structure was examined by X-ray and electron diffractions. The surface morphology was The chemical state of observed using scanning electron microscopy. element was analysed by X-ray photoelectron spectroscopy. Measurement of electrocatalytic property The electrocatalytic properties of the film-electrode were measured steady-state method. A three compartments by the galvanostic conventional double-walled thermostated glass cell was used as the electrolytic cell. The electrolysis was IN NaOH solution, prepared from analytic reagent and twofold distill water. The Ti-Ni alloy film was used as the test electrode. The counterelectrode was a platinum gauze electrode served as the with large surface area. A Hg/HgO (INNaOH) reference electrode. The electrolytic temperature was 40±0.11C. During the electrochemical measurement, the ohmic drop of electrolyte was not compensated.
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RESULT AND DISCUSSION Composition and structures of the films The chemical compositions of the two films prepared separately from TiNi and Ti 2Ni alloy targets were Tio. saNi, 0oo and Ti1 .s 9 Ni1 . oo, respectively. The results of the X-ray and electron diffraction showed that the stru
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