Electrochemical study of hydrogen absorption in polycrystalline palladium
The hydrogen reactions on polycrystalline Pd in 0.1 M NaOH at 25°C have been studied by using transients at constant potential, and by impedance spectroscopy and X-ray diffraction techniques. At potentials, E<sub>s</sub>, more positive than the reversible potential, E<sub>r</sub...
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| Autores principales: | , , , |
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| Formato: | Articulo |
| Lenguaje: | Inglés |
| Publicado: |
1991
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| Materias: | |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/119924 https://www.sciencedirect.com/science/article/abs/pii/002207289185186S |
| Aporte de: |
| Sumario: | The hydrogen reactions on polycrystalline Pd in 0.1 M NaOH at 25°C have been studied by using transients at constant potential, and by impedance spectroscopy and X-ray diffraction techniques. At potentials, E<sub>s</sub>, more positive than the reversible potential, E<sub>r</sub>, for the H<sub>2</sub> evolution reaction, the current-time response and the impedance data indicate H atom diffusion into the bulk Pd. The X-ray diffraction pattern of electrodes cathodized during 20 min at these potentials are similar to those obtained for Pd. At Es < Er, the current transients exhibit a current maximum which increases as E<sub>s</sub> moves in the negative direction. The Nyquist plot for the rising part of the transients indicates the H atom diffusion into the bulk metal and H<sub>2</sub> evolution on the Pd surface at high frequencies. The X-ray diffraction pattern of the electrodes cathodized at E<sub>s</sub> < E<sub>r</sub>, shows the presence of the βPdH phase and Pd. The experimental results indicate that different reactions take place simultaneously in this potential range: (i) H<sub>s</sub> evolution, (ii) H diffusion into the bulk Pd, (iii) nucleation and diffusion-controlled growth of the βPdH phase. Taking into account the contribution of these reactions, a model, which is able to reproduce the experimental current transients, is presented. |
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