HYDROPHILIC OXYGEN COMPLEXES ON ACTIVATED GRAPHON

Graphon samples have been reacted in air at 500°C to different carbon burn-offs up to 70% in order to produce samples of varying active surface areas. The extent of active surface area developed was measured by oxygen chemisorption at 350°C. It increased from 0.2 to a maximum of 5.2 m2/gm with increasing carbon burn-off up to 70%. In all cases the active area was less than 4% of the BET area, measured by N2 at 78°K. Adsorption of water on the activated samples, having their active sites partially or completely covered by oxygen complex, was studied between -3.3° and 20°C. The amount of water adsorbed was shown to be proportional to the area covered by oxygen. Adsorption was reversible at relative pressures below 0.4. The heat of adsorption of water over essentially all the monolayer region closely approached its heat of liquefaction; in this case completion of monolayer coverage with water occurs at p/p0 = 0.5. With the area of the water molecule taken to the 10.6 A2, which is the value calculated for hexagonal close packing, excellent agreement was found between the water adsorption area and the area covered by oxygen chemisorption. © 1968.