Rapid Microwave-Assisted Synthesis of Platinum Nanoparticles Immobilized in Electrospun Carbon Nanofibers for Electrochemical Catalysis

Abstract

A one-pot microwave-assisted synthesis method was developed to produce carbon nanofiber (CNF) supported platinum (Pt) catalyst nanoparticles as potential electrode materials for polymer electrolyte membrane fuel cells (PEMFC). CNF-supported Pt (Pt/CNF) hybrid structures were prepared through electrospinning of poly(acrylonitrile-co-N-vinylpyrrolidone) (P(AN-co-nVP)) copolymer containing PtCl2 as a precursor and subsequent microwave-assisted chemical reduction in hydrazine hydrate solution and carbonization. First, the effect of carbonization temperatures (600 to 1000 °C) on the growth of Pt nanoparticles and their electrochemical activity was studied. Uniform particle distribution with an average particle size of 4.25 nm and the highest electrochemical surface area (ECSA) (47.4 m2 g–1) were observed for the sample carbonized at 800 °C. Then microwave-assisted chemical reduction of PtCl2 in the nanofibers prior to carbonization was investigated, which resulted in better control of particle size and distribution and higher electrochemical activity. After carbonization at 800 °C of those treated with microwave-assisted chemical reduction with irradiation time of 15 and 30 s, CNF-supported Pt nanoparticles with a particle size of 1.75 and 2.85 nm and catalytic activity of 71.2 m2 g–1 and 74.6 m2 g–1, respectively, were obtained. Finally, the addition of highly conductive SWCNTs into Pt/CNF hybrids was investigated in terms of its effect on Pt particle size and distribution and electrochemical activity of hybrid materials. SWCNT-containing Pt/CNF, obtained by chemical reduction with 15 s microwave irradiation followed by carbonization at 800 °C, had nanoparticles with an average particle size of 0.86 nm and showed high electrochemical active surface area of 90.0 m2 g–1.