Graphite Intercalation Compounds As Theoretical Model For Electronic Effect Of Carbon Support On Pt Catalyst

In recent years, great attention has been paid to the direct methanol fuel cell (DMFC), in that DMFC shows great promise as high efficiency, low emission power sources. However, Platinum was easy to be poisoned by intermediates in the process of methanol electrooxidation. So that, study on improving the activity of the catalyst have been carried out increasingly.This paper firstly reviewed the fundamental mechanism of DMFC and the method to improve the preference of platinum catalyst. Graphite intercalation compound (GIC) as theory model of support was employed to explore the electronic effect of support on the preference of anode catalyst for DMFC.In the present work, graphite intercalation compound with different intercalation degree and thus different ability of electron donation were used as theoretical model for studying the electronic effect of carbon support on the catalytic activity of the anodic Pt catalyst. The intercalation degree of GIC was controlled by electrolyzing expansible graphite in sulfuric acid or saturated potassium nitrate solution for different period of time. XRD was employed to determine the interlayer spacing of the GIC, which can be used to describe the degree of intercalation of ions.An impregnation reduction method was employed to prepare GIC-supported Pt as anode catalyst. Electrodeposition method was also used to prepare the anode catalyst for DMFC. The microstructure and nanomorphology of the Pt/GIC was characterized by scanning electron microscopy (SEM). The catalytic activity and anti-poisoning of the GlC-supported Pt catalyst were investigated using cyclic voltammetry in both sulfuric acid and acidic methanol solution. Electrochemical measurement for electrooxidation of formic acid was also carried out as a model system for understanding the complex oxidation pathways, such as those for methanol. Electronic effect of support on electrocatalystic activity of anode catalyst was evaluated by examining peak current, potential of onset of oxidation and Af/A_b value. As for anionic intercalation, with increase in degree of intercalation to graphite as catalyst support, activity of catalyst for methanol electrooxidation went down. However, the value of Af/A_b, which indicates the poisoning tolerance of the catalyst to carbonaceous species accumulation increased. And as to cationic intercalation, with increase in degree of guest ionic intercalation, the forward anodic peak current density increased, and Af/A_b value also increased. This means that the activity and the anti-poisoning of the catalyst improved. Electronic effect of GIC as support on electrooxidation of methanol was very prodigious.