Acidic and basic sites on the surface of porous carbon

Thermal desorption, acid-base depletion, mass titration and calorimetric measurements on a series of porous BPL carbons are interpreted as indicating that acid surface sites are oxygen based while basic sites are associated with the carbon itself. Both acidic and basic sites were found on all carbons whether they were heat treated to 900 degrees C in nitrogen or oxidized, chemically with nitric acid or electrochemically. For the most extensively oxidized sample, the number of basic sites is approximately zero, while for a heat treated carbon the number of acidic sites is very small. An analysis for the wholly acid carbon and the entirely basic carbon yields pK(a) and pK(b) values which are characteristic of molecular keto or hydroxy carboxylic acids and Lewis bases, respectively. (C) 1997 Elsevier Science Ltd.