POISONING OF PLATINUM SURFACES BY HEXAMETHYLDISILOXANE (HMDS) - APPLICATION TO CATALYTIC METHANE SENSORS

The evolution of the catalytic activity of platinum ribbons towards me thane oxidation has been studied as a function of the exposure to hexa methyldisiloxane (HMDS) at various temperatures. Below 950 K, and at m oderate exposure, HMDS acts as an inhibitor, the surface is progressiv ely covered by patches of silica and the number of active sites decrea ses as the exposure to HMDS is increased. Above 950 K, the interaction of platinum with HMDS produces irreversibly the formation of a silica overlayer, the mechanism of the catalytic oxidation of methane is dee ply modified. The consequences on the resistance of catalytic methane sensors are analysed as a function of the working conditions. (C) 1997 Elsevier Science S.A.