Density Functional Theory Study of Iron Phthalocyanine Porous Layer Deposited on Graphene Substrate: A Pt-Free Electrocatalyst for Hydrogen Fuel Cells

Abstract

This paper details the use of ab initio density functional theory (DFT) to analyze a potential Pt-free catalyst, nonbonded iron phthalocyanine monolayer on graphene substrate (FePc/graphene), for an approximation of catalytic pathway and properties in oxidation reduction reaction of H2 and O2 to produce water. DFT calculations show that the associative mechanism, where O2 molecules chemisorbed on Fe site and prefer hydrogenation to O–OH intermediate species with ambient H+ and electron transfer followed by subsequent water formation reaction (WFR), is found to dominate for the FePc/graphene surface. Throughout the entire oxygen reduction reaction (ORR) process, the initial reduction of O2 to O–OH reaction appears to be the rate-limiting step with a reaction barrier of 0.68 eV. The complete free energy profile suggests that oxygen molecules are inherently favorable for reduction into water on FePc functionalized graphene surface.