Non-uniform strain synergistically induced by active centers driving efficient peroxymonosulfate activation: Sulfur doping-augmented oxygen vacancies

An effective catalyst, for peroxymonosulfate (PMS) activation as an example, requires at least one special structural or morphological property. Lattice strain engineering can create such a special property by disrupting the uniformity of the crystal structure. Herein, it is triggered by the simultaneous contribution of sulfur doping (Sₓ) and point defects (oxygen vacancies, OVₓ) to create non-uniform strain. Low-electronegativity S dopants with wide and polarized 3p orbitals replace the host O atoms in the lattice of pristine Co₃O₄ (denoted as S₀OV₀CO), reducing the ionic character but increasing the covalency of Co–S bonds, thereby increasing the Co's electron density in these bonds. OVₓ, meanwhile, remove O²⁻ ions, increasing the delocalization of the surrounding Co and enhancing the unoccupied states’ density of Co 3d. Therefore, the highest Sₓ level and OVₓ density synergistically make S₃OV₃CO the most efficient PMS activator after excluding specific surface area, with a normalized rate constant of 0.00854 min⁻¹⋅m⁻²⋅g (greater than 0.00751 min⁻¹⋅m⁻²⋅g for S₀OV₃CO without Sₓ). Compared with OVₓ, more appreciable in reducing the adsorption energy (-7.64 to −7.73 eV for one and two OVₓ), Sₓ enhances the activation to a lesser extent with incremental Sₓ level (-6.83 to −7.03 eV for one and two S dopants), but it simultaneously augments the formation of OVₓ. Ultimately, S₃OV₃CO/PMS is capable of forming assorted reactive species, degrading outright benzophenone-2 and tetracycline within eight minutes. This study offers a singular prospect of tailoring properties of metal oxides through non-uniform strain induced by the interplay of dopants and defects. Copyright © 2025 Elsevier B.V.