Flexible and macroporous network-structured catalysts composed of conducting polymers and Pt/Ag with high electrocatalytic activity for methanol oxidation

Abstract

Flexible and uniquely network-structured polyaniline (PANi) and polypyrrole (PPy) supported Pt and Ag catalysts were synthesized using eggshell membrane as a template and explored for the methanol oxidation reaction (MOR) for proton exchange membrane fuel cell (PEMFC) application. The scanning electron microscopy observation showed a hierarchically ordered macroporous network of PANi and PPy. Due to the difference of polymer and metal essences, Pt was in the form of nanoparticles and Ag was in the form of nanofibers on the surfaces of PANi and nanoflakes on PPy. Energy dispersive X-ray spectra, thermal gravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction patterns and X-ray photoelectron spectra were used to characterize the resultant catalysts. The results revealed that the prepared flexible catalysts had a Pt loading of 7.5 and 7.48 wt% in Pt/PANi and Pt/PPy, and a Ag loading of 11.3 and 5.78 wt% in Ag/PANi and Ag/PPy, respectively. The PANi network was in its crystalline structure, which was expected to provide very high conductivities and electrochemical properties. The cyclic voltammetric studies at room temperature showed an excellent electrocatalytic activity for MOR in acidic medium. The catalysts were also checked in the electro-oxidation of methanol at high temperatures, a much higher electrocatalytic activity at 200 °C than that at 50 °C and good stability made them potential candidates for high-temperature PEMFCs. Combined with the mechanical strength, it is believed that PANi-based catalysts are more useful in MOR applications. The excellent properties, alterable supports, simple preparation procedure and low cost allow these catalysts to be used in high-temperature PEMFCs and other fields.