Al doping-induced electron delocalization of Co3O4 boosting efficient peracetic acid activation for water decontamination

Abstract

Advanced oxidation processes (AOPs) based on peracetic acid (PAA) hold broad application prospects in pollutant degradation. Cobalt-based spinel oxides can activate PAA via the Co(II)/Co(III) redox cycle, but their intrinsic activity is largely limited by the sluggish kinetics of the Co(III)-to-Co(II) reduction step. Herein, a synergistic strategy that couples electronically inert doping with lattice strain engineering by introducing Al³⁺ into the Co₃O₄ lattice is proposed. The closed-shell electronic inertness of Al³⁺ ensures a clean catalytic cycle, while its smaller ionic radius induces lattice strain, facilitating the formation of oxygen vacancies (OVs). Density functional theory (DFT) calculations combined with in situ Raman and FT-IR reveal that the OVs modulate the local electronic structure around Co active sites, resulting in an upshift of the d-band center, which synergistically enhances PAA adsorption energy from −0.53 eV to −0.64 eV on the catalyst surface, and accelerates the crucial Co(III)-to-Co(II) reduction step, ultimately leading to significantly improved PAA activation efficiency. Using tetracycline (TC) as the target pollutant, the Al_xCo_3−xO₄/PAA system achieves an efficient degradation rate of 91.8% in 15 min (28.4% in 15 min for the Co₃O₄/PAA system), with 7.7-fold enhancement in k_obs compared to the Co₃O₄/PAA system. By integrating experimental and theoretical approaches, this work provides new insights into the modulation of electronic structures for the design of highly efficient Co₃O₄-based PAA-activating catalysts.