The low-pressure cold microwave (MW) plasma is shown as an efficient method to increase acidity of the ACF within less than I min treatment without affecting the fibre morphology and strength. The ion-exchange capacity was 1.6 times higher compared to the non-treated ACF sample. Selective removal of the carboxylic groups from the ACF surface by the air-MW-plasma allows to keep the phenolic groups intact. Palladium was deposited on ACF from [Pd(NH3)(4)]Cl-2 solution via ion-exchange with the protons of the phenolic surface groups. Sur-face phenolic groups were able to chemically anchor Pd in cationic form, leading after reduction in H-2 to small Pd degrees nanoparticles (< 3 nm). The Pd dispersion was measured by CO pulse adsorption and confirmed by the TEM analysis. Heating of the Pd/ACF catalysts in H-2 at 573773 K is necessary to reduce Pd(II) to Pd degrees. This reduction can be also achieved by the H-2-MW-plasma treatment in less than I min with the corresponding saving of energy. (c) 2005 Elsevier B.V. All rights reserved.