Synthesis of Ultrafine Pt Nanoparticles on defective Graphene Nanosheets with Enhanced Performance towards Methanol Electro-oxidation

Content Provider	Semantic Scholar
Author	Rao, Longshi Zhang, Bang Wen Sun, Shu Gang
Copyright Year	2013
Abstract	Direct methanol fuel cells (DMFCs) have been recognized as one of the av ailable energy resources due to its high energy density, low pollutant emission, low operating temperature, and ease of handling liquid fuel [1]. However, maximizing Pt utilization efficiency and reducing Pt loading still f ace big challenges [2]. The performance of Pt catalyst strongly depended on Pt particle size and Pt dispersion on the carbon support. Graphene (GS) is a planar sheet of grap hite carbon, where the carbon atoms are tightly arranged in a 2-D honeycomb like lattice, and is extensive applied in many fields. In this work, a facile and simple method was applied to prepare ultrafine Pt nanoparticles on GS. First, GS were formed by the thermal-expansion method, and then Pt nanoparticles supported on GS (Pt/GS) were synthesized through an improved impregnation approach and mixture gas (5% H 2 in N2) reduction. BET analysis proved that GS had micropores of 1.2 nm, which could be effectively used as active surface sites for anchoring Pt nanoparticles on GS. SEM and TEM images indicated the simple and clean method can effectively synthesize Pt with uniform dispersion and small size (below 3 nm) on the 2-D specific and stratiform GS (shown in Fig.1a-b). From HRTEM of Fig.1c, the crystal grains were clearly observed with the lattice spacing of 0.230 nm corresponding to the (111) plane of Pt crystal. Fig.1d depicted the powder X-ray diffractogram (XRD) of the Pt/GS. The diffraction peaks at 39.5°, 46.2°, 67.6° and 81.7° were respectively indexed to the (111), (200), (220), and (311) reflections of face-centered cubic Pt nanocrystals. The strongest p eak at 39.5° indicated the Pt/GS (20%) showing the Pt (111) preferred orientation. Fig. 1e is cyclic voltammograms of the methanol electro-oxidation on Pt/GS (20%), Pt/C (XC-72) and Pt/C (JM). Pt/GS (20%) displayed remarkable catalytic activity and prominent current peaks in both the positive and negative potential scanning. Fig. 1f is the current density-time curve ( j-t) of methanol oxidation at 0.4 V in the solution of 0.5 M CH 3OH + 0.5 M HClO4. After 1800 s the current density of methanol oxidation on Pt/GS (20%) remained 0.36 mA cm , about 2.33 times that of Pt/C (JM) (20%) (0.15 mA cm ) and 1.2 times that of Pt/C (XC-72) (20%) (0.30 mA cm ), indicating that the Pt/GS (20%) catalyst possessed the superior performance towa rd the methanol electrooxidation. The loss of elect ro-active surface area was evaluated by calculating the charge associated with H adsorption in sulfuric acid before and after the stability test. The Pt/C (JM) suffered a 17.6 % loss (from 1.27 to 1.04 cm) in catalytic surface area, whereas for Pt/GS (20%), only 8.2 % (1.14 to 1.05 cm ) of the original Pt surface area was lost, indicatin g that the synthesized GS with 1-2 nm pores could potentially provide much higher durability than the commercial carbon resource.
File Format	PDF HTM / HTML
Alternate Webpage(s)	https://ecs.confex.com/data/abstract/ecs/224/Paper_21294_abstract_4522_0.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article