Preparation and electrochemical characterization of carbon paper modified with a layer of boron-doped nanocrystalline diamond

Carbon paper (CP) was modified with a layer of boron- doped nanocrystalline diamond (BND) in order to improve the material's chemical resistance and microstructural stability during exposure to aggressive electrochemical environments. In the procedure, carbon fibers in the CP were coated up to a depth of about 50 mu m with a thin layer (ca. 1 mu m) of electrically conducting diamond. The diamond layer was deposited by microwave plasma- assisted chemical vapor deposition using an argon- rich CH4/H-2/Ar/B2H6 source gas mixture. X- ray diffraction and Raman spectroscopy confirmed the presence of a crystalline diamond overlayer. The electrodeposition of Pt electrocatalyst particles was used to probe the electrochemical activity of the diamond- coated electrode. The metal phase was formed using pulsed galvanostatic deposition (cathodic) at 1.25 mA/cm(2) (geom.) and evaluated in terms of (i) the particle size and distribution, (ii) the stability during anodic polarization, and (iii) the electrochemical activity for the reduction of dissolved oxygen. Pt particles with a diameter of 100-300 nm and a particle density of 108-109 cm(-2) were formed on all regions of the BND electrode. Importantly, the diamond- modified electrode exhibited superior morphological and microstructural stability during anodic polarization (1.4 V vs Ag/AgCl) as compared to CP, both in the presence and absence of Pt. The results demonstrate that surface modification with electrically conducting diamond is a means to improve the dimensional stability of sp(2) carbon materials, particularly those used in fuel cells.