The effect of experimental parameters on the synthesis of carbon nanotube/nanofiber supported platinum by polyol processing techniques

Developing corrosion resistant carbon nanotube (CNT) and carbon nanofiber (CNF) supported Pt catalysts with optimized particle size is important for proton exchange membrane fuel cells. We investigated the effects of deposition technique (conventional refluxing and microwave irradiation), water content, carbon support and metal loading on the average Pt particle size and electrochemically active surface area (ECSA). BET surface area measurements, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, transmission electron microscopy and cyclic voltammetry were used to characterize all the CNT/CNF supported catalysts. Processing was accelerated via microwave irradiation without significantly affecting Pt particle size as compared to conventional refluxing especially for high surface area CNT supported low Pt loading (10 wt%) catalyst. Adjusting the water content during synthesis effectively controlled the Pt particle size and size distribution regardless of the heating method, carbon support and metal loading. The ECSA of the samples was found to be dependent on Pt particle size which further depends on the water content during synthesis, support surface area and Pt loading. Optimization of deposition conditions leads to higher ECSA than seen in a commercially available carbon black supported catalyst.