Electrochemical Properties of Gold Incorporated Inside FSM-16 and Y Zeolites | ||||
| Egyptian Journal of Solids | ||||
| Article 11, Volume 25, Issue 1, 2002, Page 115-123 PDF (186.66 K) | ||||
| DOI: 10.21608/ejs.2002.150468 | ||||
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| Abstract | ||||
| The dc and ac conductivities as well as the dielectric constant (ε) were measured for different zeolites encapsulated gold (Au Cl3) catalysts at different temperatures (300-500 K) as a function of frequency (5 kHz-1 MHz). The conductivity values were found to be in the order Au/FSM-27 >Au/NaY > Au/FSM- 47. This result was confirmed by finding that the first ionization energy of Na+ ions was much lower than that of Cl ones. The conductivity of Au either in FSM-27 or FSM-47 was expected to be of electronic character where the hopping mechanism is the most predominant. Whereas, in the case of Au/NaY; containing Na and Cl ions, the conductivity was partially ionic partially electronic. Above 376 K, a metallic behavior was obtained for Au catalysts. The IR study showed that the exposure of Au zeolites to CO adsorption produced a characteristic band of Au+- CO at 2180 cm-1 that tends to decrease with temperatures and even vanish at 376 K in favor of the Auo-CO band at 2128 cm-1. Similarly, a phase transition at 338 K that extends to 376 K was confirmed by DTA to further emphasize the temperature region of the metallic Au formation. After the phase transition, the increase in thermal energy caused an increase in the lattice scattering of the charge carriers that produced a decrease in the mobility, polarizability and permitivity. | ||||
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