An average particle size of 50 nm undoped nanodiamond supported PtRu (PtRu/ND) electrocatalyst has been prepared by a microwave-assisted reduction method. Furthermore, acetylene black as an additive was introduced into the PtRu/ND electrocatalyst (PtRu/ND + C) to improve its electrocatalytic performance by increasing electrical conductivity. The two functions of conventional supporting materials involve the dispersal of the catalysts and the transfer of electrons. However, in this paper, the functions of the supporting material were separated. ND, with its high oxidation resistance, was used as the supporting material to disperse the catalysts, with the catalytic reaction occurring on its surface. Acetylene black was only used to transfer electrons and was not involved in catalysis. The electrochemical activity of PtRu/ND + C increased compared to PtRu/ND because of the combination of PtRu/ND and acetylene black. Based on the results of electrochemical measurements, the PtRu/ND + C electrocatalysts exhibited remarkably enhanced electrochemical activity and stability compared with the PtRu/ND. This could be attributed to the excellent stability of the ND support and the electro-conductive network resulting from the introduction of acetylene black. Copyright (c) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.