Investigating a New Electrocatalyst for Polymer Electrolyte Membrane Fuel Cells and the Effect of Carbon Additives in the Reaction Layer

Abstract

In this study gas diffusion electrodes for Oxygen Reduction Reaction (ORR) was prepared for Polymer Electrolyte Membrane Fuel Cells (PEMFCs) using a new electrocatalyst. For this purpose, the Pt/ZnO electrocatalyst was synthesized, and graphite and Vulcan XC-72 was used as the additive in cathode catalyst layer. This approach was designed to investigate the effect of electrical conductivity and surface area in the reaction layer. Electrochemical methods, such as linear sweep voltammetry and impedance analysis, were applied to investigate the actual role of graphite and Vulcan XC-72 in the electrodes. The addition of different carbon additives like graphite and Vulcan XC-72 improves the structure of electrocatalyst and forms a conductive and porous layer, facilitating an efficient mass transport. The network structure of the catalyst layer and its performance depends on the amount of the carbon additives. It was found that the addition of graphite and Vulcan XC-72 into the cathode catalyst layer enhanced the performance at the high current density region, probably due to an increase in the gas diffusion rate. The amount of carbon additives varied from 10 wt.% to 50 wt.% with respect to the weight of the Pt/ZnO catalyst layer used. The Pt/ZnO electrocatalyst by only 10 wt. % addition of Vulcan XC-72 shows much higher reduction current. This suggests an excellent catalytic activity for oxygen reduction in comparison with Pt/ ZnO electrocatalyst with graphite additive. Hence Vulcan XC-72 additive acts better than graphite additive due to its high surface area and pore structure.