On the Reduction of O2 on Cathode Surfaces of Co-Corrin and Co-Porphyrin: A Computational and Experimental Study on Their Relative Efficiencies in H2O/H2O2 Formation
Journal
Journal of Physical Chemistry C
Journal Volume
124
Journal Issue
8
Pages
4652-4659
Date Issued
2020
Author(s)
Abstract
The mechanisms for O2 reduction and H2O/H2O2 formation on Co–corrin and Co–porphyrin cathode surfaces of the proton exchange membrane fuel cell (PEMFC) systems have been studied by hybrid Hartree–Fock/density functional theory (B3LYP) calculations with the LANL2DZ basis set. The calculations show that the reduced Co–corrin with a single negative charge (Co–corrin–) is more reactive than the neutral Co–corrin and the doubly charged Co–corrin2–. Both O2 and O adsorptions are most stable on Co–corrin–, rather than Co–corrin or Co–corrin2–. The potential energy profiles show that the decomposition of O2 on both Co–corrin and Co–corrin– can take place energetically favorably without thermal activation. The formation of H2O and H2O2 are predicted to occur by two separate reaction paths: the HO path and the HOO path. The HO path with H2O as the predominant product on the reduced Co–corrin– surface, the energetically favored surface, under operational cathodic conditions, which is consistent with recent experimental findings, wherein the PEMFCs with pyrolyzed vitamin B12 containing Co–corrin as catalysts loaded at the cathode, can deliver up to 14.5 A cm–3 at 0.8 V with IR compensation. A similar calculation performed for a Co–porphyrin system shows a significantly less efficient O2 reduction, consistent with the experiment results of the PEMFC power output studies.
SDGs
Publisher
American Chemical Society
Type
journal article