A modified polyol process is developed to enhance the Pt loading during the preparation of carbon-supported platinum (Pt/C) catalysts. With the help of the zeta potential, the effect of pH on the electrostatic forces between the Support and the Pt colloid is investigated. It is shown experimentally that the surface charge on the carbon Support becomes more electropositive when the solution pH is changed from alkaline to acidic. This change does not, however, affect the electronegative surface charge of Pt colloids already attained and stabilized by glycolate anions. This new behaviour caused by the change in solution pH accounts for the enhanced yield of the process and does not affect the Pt particle size. All the experimental results reveal that this simple modification is a cost-effective method for the synthesis of highly Pt-loaded Pt/C catalysts for fuel cells. (C) 2008 Elsevier B.V. All rights reserved.