Ultra-low Pt loading catalytic layer based on buckypaper for oxygen reduction reaction

Buckypaper is a freestanding, self-supported and well defined membrane-like black thin film. We developed a buckypaper film containing a MWNTs-rich surface and a CNFs-rich surface. Pt nanoparticles supported on this film with an ultra-low Pt content, 0.05 mg/cm², as a catalytic layer for oxygen reduction reaction (ORR) were synthesized by a sputtering process (Pt/BP-SP). The physical and chemical properties as well as electrochemical performance of this nanocomposite were studied. For comparison, Pt nanoparticles supported on buckypaper with a Pt content of 0.10 mg/cm² were prepared by an electrodeposition process (Pt/BP-ED). The results proved that Pt/BP-SP possessed a smaller particle size and a more uniform distribution on buckypaper than Pt/BP-ED. Cyclic voltammetric investigation showed that Pt/BP-SP had a higher electrochemical surface area although its Pt content was lower than that of Pt/BP-ED. Tafel studies proved that Pt/BP-SP had a move positive equilibrium potential and a higher apparent exchange current density. Moreover, the results of linear sweep voltammetric (LSV) analysis exhibited that Pt/BP-SP had a higher ORR activity compared with Pt/BP-ED, and LSV at different rotation rates revealed that ORR on Pt/BP-SP electrode was a 4e^- process.