SURFACE AND SUBSURFACE PRODUCTS OF THE INTERACTION OF O-2 WITH AG UNDER CATALYTIC CONDITIONS

Polycrystalline Ag treated with O2 at pressures up to 1 bar and at temperatures up to 920 K was examined by TDS. It was found that the peak commonly observed at 595 +/- 25 K and assigned to adsorbed atomic oxygen (O(a)) is shifted to higher desorption temperatures with rising dosing temperatures. Since saturation of the uptake was not possible either, this peak was identified as dissolved atomic oxygen (O(d)). The existence of a maximum for the O2 uptake after exposure at 820 K was found. Hence, under conditions of formaldehyde synthesis (almost-equal-to 920 K) the ability of the catalyst to dissolve oxygen is near its maximum.