Open AccessNon-PGM Electrocatalysts for PEM Fuel Cells: Thermodynamic Stability of Potential ORR CoNx-C Electrocatalytic Sites
Author(s) -
Vassili P. Glibin,
Gaixia Zhang,
JeanPol Dodelet,
Shuhui Sun
Publication year - 2021
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ac1d03
Subject(s) - chemistry , microporous material , chemical stability , proton exchange membrane fuel cell , algorithm , materials science , membrane , computer science , organic chemistry , biochemistry
We present here a thermodynamic assessment of the stability behavior in acidic environments at 298 and 353 K (80 °C) of several Co-based sites that may potentially be active for the oxygen reduction reaction (ORR) at the cathode of proton exchange membrane (PEM) fuel cells. These sites are: i) the porphyrin-like CoN 4 /C site located in a micropore, ii) two different 1,10-phenanthroline-like CoN (2+2) /C sites located either in a micropore or embedded into a graphene sheet, and iii) the CoN (4+2) /C site having (at its center) the structural motif of the hexa-aza-macrocyclic complex of Co(II) embedded into a graphene sheet. The calculations of the equilibrium constants ( K c ) for the reactions of demetallation indicate that all evaluated active sites are chemically stable in an acidic medium at both 298 and 353 K. At 298 K, K c values for CoN 4 /C and for the two examples of CoN (2+2) /C sites are very similar. The same conclusion is also true at 353 K. However, the simple introduction of two supplementary nitrogen atoms in the structure of the embedded hexa-aza CoN (4+2) /C site vs that of the embedded phenanthroline-like CoN (2+2) /C site significantly affects its stability toward Co 2+ demetallation, rendering CoN (4+2) /C much less likely to demetallate than CoN (2+2) /C either at 298 or 353 K.