The effect of functionalising agents (KMnO4 and HNO3) on the surface properties of carbon spheres (CSs) produced from acetylene gas by a chemical vapour deposition method, was examined. Cobalt was loaded onto the differently functionalised CSs using the deposition precipitation (DPU) method and the Co/CS catalysts were tested for Fischer-Tropsch (FT) activity. FT studies, revealed differences in activity and selectivity for the HNO3 and KMnO4 functionalised catalysts. Investigation of the role of Mn (0.05%) and K (0.05%) on Co/CS FT catalysts functionalised with HNO3 revealed that these differences were due to the presence of residual MnO4- ions remaining after the surface functionalisation reaction. (C) 2011 Elsevier B.V. All rights reserved.