Deciphering the dual-regulatory mechanism of Zn doping in spinel ZnCo₂O₄ for piezoelectric-activated peroxymonosulfate: Steering the high-valent cobalt-oxo pathway.

Developing highly efficient piezocatalytic systems requires effectively synchronizing mechanical energy harvesting with surface redox chemistry. Herein, we report a dual-regulatory strategy utilizing a spinel ZnCo₂O₄ piezoelectric catalyst for ultrasound-assisted peroxymonosulfate (PMS) activation. We demonstrate that Zn substitution within the Co₃O₄ lattice precisely modulates both its physical and chemical properties. Physically, Zn-induced lattice distortion significantly enhances the piezoelectric response (d₃₃ = 95.8 pm/V), providing a robust driving force for charge separation. Chemically, it upshifts the Co d-band center and promotes oxygen vacancy formation, optimally tuning PMS adsorption. Consequently, the optimized ZnCo₂O₄ exhibits exceptional piezocatalytic activity, degrading 2,4-dichlorophenol at a rate 3.6 times faster than pristine Co₃O₄. Crucially, quantitative analyses and density functional theory calculations reveal a non-radical pathway largely mediated by high-valent Co(IV)=O species. The synergy between this tailored electronic structure and external stress drastically lowers the energy barrier for the rate-determining O-O bond cleavage to merely 0.52 eV during Co(IV)=O formation. Demonstrating robust practical viability, this system achieves >97% chemical oxygen demand removal in real landfill leachate concentrate. This study provides fundamental atomic-level insights into coupling piezoelectricity with intrinsic catalytic activity, establishing a powerful paradigm for mechanical-energy-driven environmental remediation.