Platinum nanoparticles electrodeposited on diamond substrate show poor stability. Their electrochemical activities vary with different substrates and deposition methods. In this study Pt nanoparticles were prepared using a two-step deposition method. The stability and electrochemical activities of Pt nanoparticles on diamond were investigated in detail. The deposition method includes a wet-chemical seeding process and an electrochemical overgrowth of the seeds. The wet-chemical seeding process can be applied as well for other kinds of metal particles on diamond. H-terminated diamond surface is more favorable for seeding than O-terminated surface. Rapid thermal annealing process was applied to enhance the stability of Pt particles on diamond. Electrochemical activation and further overgrowth of annealed Pt nanoparticles were applied to improve the hydrogen adsorption/desorption activities of Pt nanoparticles on diamond with cyclic voltammetry in 0.1 M sulfuric acid solution. As confirmed by ultrasound removal and atomic force microscope (AFM) removal experiments as well as electrochemical tests, highly stable and active Pt nanoparticles on diamond were achieved after thermal annealing and electrochemical activation/overgrowth processes. (C) 2013 Elsevier Ltd. All rights reserved.