Addition of non-metallic elements such as N, P and S was examined to reduce the catalyst particle size of PtRu deposited on a carbon support and to improve the catalytic performance. It was found that the addition of N, P and S reduced the size of PtRu catalyst particle and that P was the most effective additive on the size reduction. A well dispersed PtRu catalyst particle 2 nm in size was obtained by the addition of P. The maximum power density was observed to be 64 mW/cm(2) in a passive state of direct methanol fuel cell (DMFC) at room temperature by using the PtRuP anode catalyst. The PtRuP catalyst retained the size independently with surface area of the carbon support. This made it possible to use a carbon support with low surface area (lower porosity), resulting in better accessibility by molecules on the noble metal particles which were deposited prior to the external surface in compared to the micropore walls. The maximum power density was improved from 44 to 64 mW/cm(2) by using a less porous carbon support (140 m(2)/g). (c) 2005 Elsevier B.V. All rights reserved.