Electrocatalytic Study of Cu/Ni Metal Organic Frameworks (MOFs) and its Graphitic Carbon Nitride (g-C3N4) Composites for Methanol Oxidation Reaction in DMFC

Abstract

Direct Methanol Fuel Cells (DMFCs) are the excellent source of portable power supply, they offer various advantages such as low working temperature, less emission of pollutants, high energy density and ease of mobility of Methanol as fuel. Fuel cells are the way towards green environment with its application reaching landmark where it can be employed on mass scales for consumer usage. Previously used catalyst such as Pt, Rh, Ru and Pd being expensive, faced the challenge of catalyst poisoning and slow reaction kinetics. The solution to these problems is an effective, low cost and efficient catalyst which can benefits the advantages of noble catalyst while suppressing the negatives faced by them. This research work involves the synthesis of novel bimetallic Cu/Ni MOF and composites of Cu/Ni MOF with graphitic carbon nitride (g-C3N4) as electro-catalyst for the oxidation of methanol in DMFC. Hydrothermal method was used to synthesize the electro-catalyst and to increase the stability and electrochemical properties of it, g-C3N4 was added to the Cu/Ni MOF. The weight percentage of g-C3N4 varies from 1% to 5% and 8%. Addition of g-C3N4 to Cu/Ni MOF proved to be helpful in increasing the catalytic activity as well as conductivity, among all the composites Cu/Ni MOF @ 5wt%- g-C3N4 has shown the best result in term of Current density which is reported as 103 mA/cm2 . Generally, increasing the concentration of g-C3N4 enhances the catalytic activity and hence the current density but up to the certain level. As Cu/Ni MOF @ 8wt%- g-C3N4 has inferior catalytic properties as compared to Cu/Ni MOF @ 5wt%-g-C3N4, due to the domination of g-C3N4 on active sites of catalyst. Characterization of samples was done by SEM, XRD and FTIR. XRD described the crystallinity of catalyst and reflected that g-C3N4 has no effect on crystallinity of catalyst. SEM revealed information about morphology of catalyst and FTIR confirmed the presence of functional group in catalyst. Electrochemical studies were carried out using CV, EIS and Chronoamperometry tests. The relative stability of Cu/Ni MOF @ 5wt%- g-C3N4was maximum as 19.31 % for the passage of one hour while EIS study show that lowest charge resistance is of Cu/Ni MOF @ 5wt%- g-C3N4