Tuning 4f-2p-3d gradient orbital coupling in perovskite heterointerfaces to optimize Co²⁺/Co³⁺ redox cycling for...

Co-containing perovskite oxides show great potential in peroxymonosulfate (PMS)-mediated water purification due to their unique 3d orbital electronic configuration, but face challenges in sustainable redox cycling. This study proposes a strategy to modulate Co spin states by constructing a heterointerface. La(OH)₃ nanoparticles were composited with SrCoO_3-α (SC) to form an SrCoO_3-α/La(OH)₃ (SC/LH3) heterostructure, achieving d-p-f orbital gradient coupling at the interface. The orbital gradient coupling at the interface modulated the electronic structure and coordination environment of the Co site, increasing the e_g electron occupancy to 0.940, which approaches the theoretical optimum value. The SC/LH3 catalyst activated 72.90% of PMS to form a synergistic effect between ¹O₂ and SO₄^•-. The SC/LH3/PMS system attained 98.90% enrofloxacin (ENR) abatement within 7 min (k_obs, 0.668 min^-1) and 3.4-fold improvement over that of SC. The system also demonstrated exceptional stability, with degradation efficiency decreasing by only 0.82% after five cycles. The continuous-flow membrane reactor maintained an ENR removal rate of 91.73% after 27 h of continuous operation. The exceptional degradation performance of SC/LH3 stems from the optimized electronic structure of the Co site, which enhances both the adsorption and dissociation capabilities of PMS. Furthermore, the enhanced reducibility of Co³⁺ in SC/LH3 is crucial for ensuring the catalyst's cycling stability. This study offers a promising strategy for designing catalysts through the engineering of surface interfaces and electronic configurations.