Density Functional Theory Study of FePc Functionalized Graphene: A Potential Non-precious Pt-free Cathode Catalyst for Fuel Cell
Sean Mussel and Pabitra Choudhury
Department of Chemical Engineering, New Mexico Tech, Socorro, NM
Fuel cells offer a high potential for commercial and industrial use, however, severe shortcomings of current technology, which needs to be overcome to make them economically enticing at low temperature. One of the main cost prohibitive features of fuel cells is the use of large amount of platinum catalysts on both electrodes. One of the most important barriers for complete fuel cell reactions is related to the slow rate of cathode reaction where O2 is reduced, known as oxygen reduction reaction (ORR). In spite of Pt catalyst is being used on the cathode electrode, the kinetics is much slower than that of anode reaction. Recently, non-precious metal catalysts make replacement of Pt in ORR electrocatalysts with earth-abundant elements such as Fe, Co, N and C have also been realized. As such, there is also an interest in reducing the amount of PGM in the cathode catalysts. However, over potential associated with the ORR reaction on cathode catalysts is also one of the major concerns. Our hypothesis is that nonprecious single metal atom based catalyst center will not only reduce both cost & energy barrier for ORR reaction but also reduce the over potential associated with cathode catalysts. So, single metal atom based catalyst center such as metal phthalocyanine has been tested on a graphene substrate for ORR. In this study, we have used first principles density functional theory (DFT) calculations to study the structural, energetics and catalytic ORR reaction on Iron-phthalocyanine (FePc) and Copper-phthalocyanine (CuPc) functionalized graphene. The fundamental reaction mechanisms, how the non-precious single metal atom based catalyst and/or support affects the ORR rate at the electronic structure level will be discussed. Finally, we will also discussed the role of the central metal atom, ligand and several single bridging atoms for tunable catalytic properties during ORR on the cathode electrode.
DFT calculation work was also supported from NSF TeraGrid (XSEDE) resources under allocation number [TG-DMR140131]. Use of the Center for Nanoscale Materials was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.