Five carbon black supports with medium surface area about 400 m2 g-1 were studied for deposition of 60 wt. % platinum from aqueous solutions of hexachloroplatinic acid by impregnation. The catalysts were compared in terms of X-ray diffraction, Laser Raman spectroscopy, pulse H2 chemisorption, electrocatalytic properties and electrochemical accelerated stress testing. The deposited Pt exhibited crystallite sizes of about 3.6–8.0 by H2 chemisorption. The calcination of the dried catalysts prior

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... their reduction led to higher interaction of the hexachloroplatinic acid with the supports, which resulted in greater electrochemical stability. Dechlorination of the reduced catalysts was performed to decrease the residual content of chlorine species, which resulted in a 1.1–1.7-fold increase in the Pt crystallite size but did not alter the surface area or the electrochemical performance significantly. All of the prepared catalysts exhibited similar electrochemically active surface area, about 30 m2 gPt-1, and all showed higher specific electrocatalytic activities toward the oxygen-reduction reaction than that of the commercial high-surface-area reference catalyst, while their mass-specific activities were slightly lower. All five catalysts showed better electrochemical stability of the support than the reference, while the stability of the Pt particles was better for one of them, catalyst Pt/CB3.