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

摘要

Reduced graphene oxide has recently attracted great attention due to itsunique chemical and physical properties. In this study, reduced graphene oxide isintroduced in direct methanol fuel cell application as this system had been delayed byseveral reasons which are related to the lack of materials with good methanolpermeability and conductivity properties. Therefore, the objective of this research isto develop and characterize a high conductive reduced graphene oxide as additive inmembrane electrode assembly (MEA). Reduced graphene oxide was prepared usingreduction of the oxide with different reducing agents and the degree of reducibility ofthe reducing agents used was compared in order to determine the alternative reducingagent to replace hydrazine. The reduced graphene oxide was successfully preparedfrom the pristine graphite by reductive precipitation of graphene oxide aqueoussolution using sodium borohydride which acted as the reducing agent for 24 hoursreaction time at room temperature. Subsequently, MEA from sulfonated poly (etherether ketone) (SPEEK) consists of reduced graphene oxide as additive was fabricatedfor direct methanol fuel cell (DMFC) performance testing. The physicochemicalproperties of the reduced graphene oxide were characterized by Fourier transforminfrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electronmicroscopy (TEM) and conductivity measurement. The FTIR spectrum of thereduced graphene oxide shows that the carbonyl group was successfully removed andthe reduced graphene oxide contains some water. The XRD spectrum shows reducedgraphene oxide has hexagonal structured crystal with a sharp peak at 2θ = 26.4owhich can be assigned as 002 peak associated with reduced graphene oxide. Theexhibited conductivity was in the range of 1.80 × 103 – 1.30 × 104 S m-1. TEMmicrograph showed that reduced graphene oxide has multilayer structures. TheDMFC performance of the blended reduced graphene oxide with SPEEK55 exhibitedsubstantial improvement by 5 – 15% of open circuit voltage (OCV), initial voltage,power density, and stabilization period as compared to the commercial nafionmembrane. In conclusion, reduced graphene oxide is a potential material as catalystsupport in MEA and additive in SPEEK55 membrane to improve the DMFCperformance.