Electrodeposition of metals by sebald

Oxygen reduction reaction (ORR) and Oxygen Evolution Reaction (OER) play an important role in electrochemical energy conversion systems and in several industrial processes. Bifunctional oxygen/air electrodes are a prerequisite for the development of rechargeable metal/air batteries and/or so called regenerative fuel cells. In fact oxygen is consumed during the battery discharge that produces energy, whereas it is again formed during the battery charge when electrical energy is given to the cell. However, both ORR and OER require high overpotentials that can be lowered only using effective catalysts. The most effective catalyst is still represented by Pt, and research in the field is increasingly directed to limit the amount of catalyst and to move towards less expensive materials. In our work we tried to follow both goals: in fact we used a less precious metal like silver, whose catalytic properties have been reported long ago [1-5], but also succeeded in limiting its amount by depositing a few g cm-2 on glassy carbon. An important result of our experiments was the set up of an activation protocol based on oxidation/reduction cycles that induce the formation and redissolution of oxides of Ag (I) and Ag(II). The catalytic effects towards both ORR and OER increase progressively while increasing the amount of silver. However, the thickest Ag deposit investigated was of about 16 g cm-2, that corresponds to a theoretical thickness of about 26 nm. This value has been calculated assuming that a monolayer of silver contains about 1.2.1015 atoms and that its thickness corresponds to the lattice parameter (about 0.41 nm)