Current research has widely applied heteroatom doping
for the promotion
of catalyst activity in peroxymonosulfate (PMS) systems; however,
the relationship between heteroatom doping and stimulated activation
mechanism transformation is not fully understood. Herein, we introduce
nitrogen and sulfur doping into a Co@rGO material for PMS activation
to degrade tetracycline (TC) and systematically investigate how heteroatom
doping transformed the activation mechanism of the original Co@rGO/PMS
system. N was homogeneously inserted into the reduced graphene oxide
(rGO) matrix of Co@rGO, inducing a significant increase in the degradation
efficiency without affecting the activation mechanism transformation.
Additionally, S doping converted Co3O4 to Co4S3 in Co@rGO and transformed the cooperative oxidation
pathway into a single non-radical pathway with stronger intensity,
which led to a higher stability against environmental interferences.
Notably, based on density functional theory (DFT) calculations, we
demonstrated that Co4S3 had a higher energy
barrier for PMS adsorption and cleavage than Co3O4, and therefore, the radical pathway was not easily stimulated by
Co4S3. Overall, this study not only illustrated
the improvement due to the heteroatom doping of Co@rGO for TC degradation
in a PMS system but also bridged the knowledge gap between the catalyst
structure and degradation performance through activation mechanism
transformation drawn from theoretical and experimental analyses.