Recent Trends in Electrocatalysis - Adsorption of Oxygen Species on Ag Electrodes and the Mechanism of H2O2 Reduction
Научная публикация
| Общее |
Язык:
Английский,
Жанр:
Статья (Full article),
Статус опубликования:
Опубликована,
Оригинальность:
Оригинальная
|
| Журнал |
Transactions of the SAEST
ISSN: 0036-0678
|
| Вых. Данные |
Год: 1999,
Том: 34,
Номер: 3-4,
Страницы: 88-92
Страниц
: 5
|
| Авторы |
Doblhofer Karl
1
,
Flatgent Georg
1
,
Radhakrishnan Ganesan
1
,
Pettinger Bruno
1
,
Savinova Elena
1
,
Wasle Sabine
1
|
| Организации |
| 1 |
Fritz-Haber-Institut, Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
|
|
In-situ surface enhanced Raman spectroscopy (SERS) and ex-situ X-ray photoelectron spectroscopy (XPS) can be employed successfully for detecting oxygen-containing species on single crystal silver electrodes. From such experiments the mechanism of Ag(111) premonolayer oxidation in alkaline electrolyte is derived. The cathodic reduction of hydrogen peroxide on silver electrodes in acidic electrolyte can proceed by two parallel mechanisms. First, by the "normal" mechanism that has been discussed in the literature, second, by a novel mechanism that operates at a significantly smaller overvoltage. It is deduced that this second mechanism involves as an activating species adsorbed hydroxide, OHads, as known from premonolayer oxidation of the electrode. Since this adsorbate is unstable in the acidic electrolyte, it is concluded that a non-equilibrium coverage is generated in the course of cathodic H2O2 reduction, where OHads is known to form as an intermediate. ConsequeNtly, the second H2O2 reduction mechanism is considered to be of the autocatalytic type. It yields an N-shaped current/voltage curve and current oscillations. The conclusions are tested by model calculations.