The direct methanol fuel cells (DMFCs) have been received much attention as promising energy converters in the portable application because of high energy density, low operating temperature, low fuel price and low pollutant emission. However, although there are many advantage of DMFC, commercialization of DMFCs is difficult due to poor methanol oxidation kinetics, nondurable Pt-based catalysts, expansive price and poison of Pt by formation of CO-like intermediates ^[1]. To overcome these problems, many studies have progressed with numerous scientists. One of the methods is to modify supports like carbon material.

Among many carbon materials such as carbon black, carbon nanotubes, graphene and carbon fiber, the graphene have unique properties which are planar structure, high surface area and outstanding mechanical and chemical properties ^{[2, 3]}. However, the Pt-graphene used in fuel cell has low electrocatalytic activity because of weak interaction between the graphene used as support and Pt particles. Recently, to overcome the low electrocatalytic activity, many efforts for modification of RGO surface have been devoted. It has been studied by considering conducting polymer, and surfactant dispersant and substitution materials of functional groups ^[4,5]. The key point for maximizing elelctrocatalytic acticity is dipersion, particle size and chemical composition of Pt particles.

In this study, we present Platinum (Pt) supported thiol-attached reduced graphene oxide (RGO-S). The functional groups of GO were substituted for thiol (SH), which result from strong nucleophilic substitution reaction. The sulfur (S) that has high affinity to metal combines with Pt by strong covalent bond. In conclusion, The RGO-S-Pt composite was synthesized and showed that the RGO-S-Pt composite was better than RGO-Pt composite in terms of electrocatalytic activity. Also, the electrocatalytic activity was different according to the various weight ratios of thiol. Especially, the RGO-S-Pt composite that has weight ratio of one (GO) to five (SH) presented the highest performance in terms of electrocatalytic acticity.

Acknowledgments

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning, Korea (Grant No.: NRF-2011-0009007).

 

References

[1] Y. Zhao, L. Zhan, J. Tian, S. Nie, Z. Ning, Electrochim. Acta, 56 (2011) 1967

[2] J.Y. Park, S. Kim, J. Electrochem. Soc., 161(4) (2014) F518.

[3] C. Song, S. Kim, J. Electrochem. Soc., 162(10) (2015) F1181.

[4] J. Debgupta and V. K. Pillai, Nanoscale, 5 (2013) 3615

[5]  Q. L. Zhang, T. Q. Xu, J. Wei, J. R. Chen, A. J. Wang and J. J. Feng, Electrochim. Acta, 112 (2013) 127