Development of modified electrode systems for methanol fuel cells

In this study, platinum (Pt) based modified electrode systems were developed to use in direct methanol fuel cells. The modification process was carried out in two steps as electrochemical pretreatment and electrochemical Pt coating. Electrochemical pretreatment led to the formation of more suitable surface on pencil graphite electrode (PGE) for the electrochemical Pt coating. The electrochemical Pt coating process was carried out in a larger potential range (2V:-1V) than the conventional potential range (0V:-1V) used for the reduction of Pt. Pt coating process which was performed in a wide potential range resulted the simultaneous oxidation of the PGE during the coating. This increased the amount of the functional group on the electrode surface and the conductivity of the electrode which increased the amount of Pt coating on the electrode surface. It was observed that the methanol oxidation activity of the modified PGE increased significantly. When the electrochemical Pt coating was performed in wide potential range, the methanol oxidation activitiy of the modified electrode increased 4.8 times according to the classical electrochemical Pt coating. The methanol oxidation activity of the modified electrode was also increased 3.4 times by the electrochemical pretreatment which was performed in the mixture of hydrochloric acid and lithium perchlorate. At optimal conditions, the increase in the activity of the electrode reached to 57.7 times. It was observed that the prepared Pt based modified electrode had high stability according to the literature. Finally, the electrochemical surface area was calculated as 39.46 m2g-1. This value was 59% higher than the commercial Pt/C catalyst (24.8 m2g-1). The results show that the proposed modification process can be a rapid and easily applicable alternative catalyst preparation method for the Pt based catalysts which are used in direct methanol fuel cells.