Optimization of sulfur-doped graphene as an emerging platinum nanowires support for oxygen reduction reaction

The slow kinetics of the oxygen reduction reaction (ORR) on platinum catalyst is a critical parameter for application in polymer electrolyte membrane fuel cells (PEMFCs). Herein, we study the effects of sulfur on the electrochemical activity and stability of sulfur doped graphene supported platinum nanowires (PtNW/SGs). To investigate the influence of sulfur, a series of sulfur-doped graphene materials with varying sulfur contents ranging from 0.35 to 3.95 at% are applied as platinum nanowire catalyst supports. Based on the physico-chemical characterizations, electrochemical measurements and density functional theory (DFT) calculations, we find that the amount of sulfur significantly affects the electrokinetics of the Pt nanowires. The best ORR kinetics are observed for the platinum nanowires supported on graphene with 1.40 at% sulfur, showing a mass activity of 182 mA/mg(Pt) and a specific activity of 662 mu A/cm(Pt)(2) at 0.9 V vs. RHE. At this sulfur content, well-defined platinum nanowires with diameters in the range of 4-16 nm are observed that are beneficial for enhancing ORR kinetics. (C) 2015 Elsevier Ltd. All rights reserved.