Morphology-dependent surface phosphorylated Co3O4 for enhanced chlorobenzene oxidation and chlorine resistance

Morphology engineering is an effective strategy to regulate the catalytic performance of transition metal oxides for chlorinated volatile organic compound (CVOCs) elimination, yet the morphology-dependent response to surface modification and its intrinsic mechanism remain insufficiently understood. Herein, cubic Co 3 O 4 -c and plate-like Co 3 O 4 -p with distinct surface defect densities were selected as model catalysts to systematically reveal the morphology-dependent effect on chlorobenzene (CB) oxidation, with surface phosphorylation employed as a regulated means to probe the intrinsic morphology-dependent regulation mechanism. Surface phosphorylation exhibits a significant morphology-dependent feature. It retains the intrinsic spinel structure of Co 3 O 4 and triggers surface electronic redistribution via constructed Co–O–P bonds. High-defect Co 3 O 4 -p presents favorable responsiveness to phosphorylation, which synchronously boosts acid sites, surface Co 3 + proportion and adsorbed active oxygen content. By contrast, phosphate species partially cover surface active sites of low-defect Co 3 O 4 -c, leading to activity decline. The optimized HP-Co 3 O 4 -p delivers a T 90 value of 330 ℃ toward CB combustion, 23 ℃ lower than pristine Co 3 O 4 -p, and retains 84% conversion after 10 h reaction with mitigated attenuation. Mechanism analysis demonstrates that the morphology-dependent effect originates from the difference in surface defect density. On high-defect Co 3 O 4 -p, P–OH groups supply protons to facilitate C–Cl bond activation and HCl desorption, and phosphate moieties alleviate chlorine enrichment and restrain polychlorinated byproducts. This work reveals the morphology-dependent phosphorylation mechanism of Co 3 O 4 and guides the rational design of efficient CVOCs catalysts.