The synthesis, characterization, and performance of carbon nanotubes and carbon nanofibres with controlled size and morphology as a catalyst support material for a polymer electrolyte membrane fuel cell

Carbon nanotubes (CNTs) and carbon nanofibres (CNFs) were synthesized by the thermal chemical vapour deposition (CVD) process using an Ni-MgO catalyst. The Ni-MgO catalyst was treated by a mechanochemical (MC) process to govern its size and morphology. The grinding time in the MC process and pyrolytic temperature in the CVD process are regarded as the main factors to tailor the size and morphology of the CNTs and CNFs synthesized. CNTs with a diameter 25 and 15 nm, twisted CNFs with a diameter 65 and 100 nm, and straight CNFs with a diameter 70 nm were synthesized. After purification, they were used as the electrode platinum support for fuel cell application. 20% Pt was loaded on the CNTs and CNFs. The fuel cell performance with twisted CNFs was found to be better than that with straight CNFs, and the performance of CNTs and CNFs with smaller diameter was better than that of bigger ones. The best performance of the fuel cell voltage of 645 mV at a current density of 500 mA cm-2 was given by twisted CNFs with diameter 65 nm. The dispersal of the loaded Pt and the resistivity of the membrane electrode assembly were considered to affect their performance.