ic9b02663_si_001.pdf (1.19 MB)
Probing Heteroatomic Dopant-Activity Synergy over Co3O4/Doped Carbon Nanotube Electrocatalysts for Oxygen Reduction Reaction
journal contribution
posted on 2019-12-12, 22:44 authored by Aiai Zhang, Jinfang Wu, Lei Xue, Shan Yan, Shanghong ZengUnderstanding and predicting how heteroatomic dopants
of carbon
nanotubes (CNTs)-based catalysts alter their catalytic performance
at nanoscale is essential to design superior electrocatalysts for
oxygen reduction reaction (ORR). This report describes findings of
an investigation of the heteroatomic dopant-activity relationship
for Co3O4/doped CNTs catalysts with different
heteroatoms including N, O, and P atoms in ORR. By using an array
of techniques to probe the structure and elementary valence of the
catalysts, the incorporation of the Co3O4 nanoparticles
can introduce defects into the doped CNTs, especially the N-CNTs,
which should contribute to the generation of active sites. The Co3O4/N-CNTs are shown to exhibit both the highest
ORR activity and stability compared with Co3O4/O-CNTs, Co3O4/P-CNTs, and Co3O4/CNTs, manifesting the synergistic correlation of Co3O4 nanoparticles, heteroatoms, and CNTs. This kind of
synergy is assessed by density functional theory calculations based
on the electronic properties and molecular orbitals. It is found that
N, O, or P atoms can tune the charge distribution of CNTs by decreasing
the lowest unoccupied molecular orbital–highest occupied molecular
orbital energy gap, thus activating the adjacent C atoms. And the
addition of Co3O4 will further redistribute
the charge of CNTs from CNTs to Co3O4 toward
enhanced ORR activity. Moreover, the Co3O4/N-CNTs
catalyst exhibits a maximum structural stability due to the strong
electronic interaction between Co2+ ions and N atoms, which
is believed to result in its high ORR stability. Analysis of the results,
along with a combined theoretical and experimental study, has provided
implications for the design of catalysts with controlled activity
and stability for ORR.