Modification of multi-walled carbon nanotubes surface by urea and its evaluation as electrocatalyst support for palladium in oxygen reduction reaction

Fuel cells are considered as a source of green energy of the past two decades. Polymer electrolyte membrane fuel cells (PEMFC) are devices in which, hydrogen and oxygen electrochemically react and produced water, electricity and heat. Basic cell is formed of two cathode and anode electrodes, which separated by an electrolyte. Electrode is made of three-phase of catalyst, ionomer and substrate. catalyst particles should have a good electrical connection with the carbon substrate and are in close contact with the membrane [1]. Insufficient catalytic activity and durability are key barriers to the commercial deployment of PEMFC. Recent observations suggest that carbon-based catalyst support materials can be systematically doped with nitrogen to create strong, beneficial catalyst-support interactions which substantially enhance catalyst activity and stability [2]. To study the effect of the catalyst, the three phase interface and evaluate the oxygen reduction reaction, a homemade half cell test was used. The half cell which made in the lab, has oxygen injection capability from one side and on the other side has proton conductivity from the solution to three phase interface. The part of half cell which is in contact with sulfuric acid, including nafion (for proton transfer of solution) and the other side consists of commercial gas diffusion layer (GDL) to conduct the distribution of oxygen to the interface is threephase. Multi-wall carbon nanotubes(MWCNT) were used to modification with urea. Pd nanoparticles on modified multiwalled carbon nanotubes (Pd-urea /MWCNT) catalysts have been prepared by an intermittent microwave heating (IMH) technique[3]. From the synthesized material, the catalyst ink was made and placed on the GDL by dropping. The electrode hot-pressed to the Nafion and placed in the half-cell. Electrochemical Measurements such as Cyclic voltammetry (CV), Electrochemical Impedance Spectroscopy(EIS) and Linear sweep voltammetry (LSV) use for evaluation. The electrochemical data of Pd-urea/MWCNT obtained were compared with Pd/MWCNT and commercial Pd/C for efficiency and stability, and the results indicate that improvement has been achieved.