(190e) A Theoretical Study on Enhanced ORR Activity and Bifunctionality of Fepc-Functionalized Graphene Via Substrate Doping, Ligand Exchange, and/or Defect Incorporation

This work analyzes the tuning of a potential Pt-free fuel cell catalyst, an iron phthalocyanine monolayer supported on a graphene substrate (GFePc) via the ligand exchange of FePc, substate doping, and defect incorporation into the graphene substrate. Boron and nitrogen are chosen as substrate dopants due to their comparability to carbon in size. Two of the most common graphene defects, single and double (585) vacancies, are chosen to represent defects that can naturally occur on the graphene substrate. Tetra-substituted phthalocyanines (carboxy-, nitro-, and amino-) and hexadeca-substituted phthalocyanines (chloro-, fluoro-, and amino-) were tested due to their availability in the current market. Utilizing ab inito spin polarized density functional theory (DFT) calculations, the dominating pathways of both the oxygen reduction (ORR) and oxygen evolution reactions (OER) have been simulated along with defining their rate-limiting step to quantify the ORR/OER overpotentials (indicator of catalyst reactivity/performance). The DFT results show that ~1 at. % boron doping in conjunction with a mono-vacancy graphene substrate offers the best performance in both ORR and OER reactions. The volcano correlation between electronic descriptors and ORR overpotential for modified GFePc systems to aid in simplifying the catalyst screening process will also be discussed. The present study allows for expanded understanding and definition of substituted iron phthalocyanine functionalized graphene and the effects that the tested substituents have on GFePc’s performance as a potential bifunctional single-metal-atom based fuel cell catalyst.

Acknowledgements: The work is supported by ACS-PRF [58740-UR6] and used the Extreme Science and Engineering Discovery Environment (XSEDE) TACC at the stampede2 through allocation [TGDMR140131]. This work utilized resources from the University of Colorado Boulder Research Computing Group, which is supported by the National Science Foundation (awards ACI-1532235 and ACI-1532236), the University of Colorado Boulder, and Colorado. PCC Cluster, NM Consortium, NM.