Synthesis and characterization of some porphyrin molecules as potential electrocatalyst for fuel cell

Olajide, Afusat Ajoke (2016)



This study synthesized and characterized two negatively charged porphyrin molecules and four positively charged metalloporphyrins, fabricated porphyrin nanostructures using various combination of the negatively charged molecules and the studied the electronic properties of the nanostructures formed. This was with a view to fabricating of nanostructures that could be used as electrocatalyst for fuel cells. Porphyrin nanostructure were fabricated using two oppositely charged porphyrin molecules. The negatively charged molecules were meso-tetra (4-sulphonatophenyl) porphyrin (TPPS44-) and meso-tetra (4-carbonxyphenyl) porphyrin (TCPP4-) and the positively charged molecules were protonated to generate the positively charged species [zinc, nickel, cobalt and manganese meso- tetra (4-pyridyl) porphyrin (ZnTPyP4+, NiTPyP4+, CoTPyP4+ and MnTPyP4+]. They were synthesized following standard synthetic methods and characterized using ultraviolet-visible spectrophotometry, infrared spectrophotometry, 1H and 13C nuclear magnetic resonance and mass spectrometry. The porphyrin nanostructure were fabricated by ordinary electrostatic self -assembly and phase transfer self–assembly and characterized using ultraviolet-visible spectrophotometry only. All the spectroscopy data confirmed the structure of the synthesized compounds. The electronic spectra of TPPS-MTPyP (M=Zn, Ni, Co and Mn) using ordinary electrostatic self-assembly technique showed the typical J-aggregation influenced by TPPS with bands around 492 nm and 708 nm. These bands were absent in the case of TCPP-MTPyP instead, there was a shift of the absorption bands to shorter wavelength, indicating H-aggregation. For the phase-transfer electrostatic self-assembly technique, the electronic spectra were quite complex and bands were narrower than expected for aggregation. This study concluded that ordinary electrostatic self-assembly was more effective method for the fabrication of nanostructure than the phase transfer method in producing a robust and well-defined porphyrin nanostructures.