Preparation and properties of reduced graphene oxide for direct methanol fuel cell application

Abstract

Reduced graphene oxide has recently attracted great attention due to its unique chemical and physical properties. In this study, reduced graphene oxide is introduced in direct methanol fuel cell application as this system had been delayed by several reasons which are related to the lack of materials with good methanol permeability and conductivity properties. Therefore, the objective of this research is to develop and characterize a high conductive reduced graphene oxide as additive in membrane electrode assembly (MEA). Reduced graphene oxide was prepared using reduction of the oxide with different reducing agents and the degree of reducibility of the reducing agents used was compared in order to determine the alternative reducing agent to replace hydrazine. The reduced graphene oxide was successfully prepared from the pristine graphite by reductive precipitation of graphene oxide aqueous solution using sodium borohydride which acted as the reducing agent for 24 hours reaction time at room temperature. Subsequently, MEA from sulfonated poly (etherether ketone) (SPEEK) consists of reduced graphene oxide as additive was fabricated for direct methanol fuel cell (DMFC) performance testing. The physicochemical properties of the reduced graphene oxide were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electronmicroscopy (TEM) and conductivity measurement. The FTIR spectrum of the reduced graphene oxide shows that the carbonyl group was successfully removed and the reduced graphene oxide contains some water. The XRD spectrum shows reduced graphene oxide has hexagonal structured crystal with a sharp peak at 2θ = 26.4owhich can be assigned as 002 peak associated with reduced graphene oxide. The exhibited conductivity was in the range of 1.80 × 103 – 1.30 × 104 S m-1. TEM micrograph showed that reduced graphene oxide has multilayer structures. The DMFC performance of the blended reduced graphene oxide with SPEEK55 exhibited substantial improvement by 5 – 15% of open circuit voltage (OCV), initial voltage,power density, and stabilization period as compared to the commercial nafion membrane. In conclusion, reduced graphene oxide is a potential material as catalyst support in MEA and additive in SPEEK55 membrane to improve the DMFC performance.