Tuning Oxygen Defects in Co-Substituted LaMnO3 Perovskites for Efficient Visible-Light Formaldehyde Oxidation

Coupling oxygen-defect chemistry with charge-transfer dynamics in perovskite catalysts for formaldehyde (HCHO) photocatalytic abatement under mild conditions remains challenging. Herein, a continuous series of LaMn 1-x Co x O 3 perovskites was synthesized via a facile Pechini method to elucidate the role of B-site Co substitution in visible-light-driven HCHO oxidation. The optimal composition, LaMn 0.67 Co 0.33 O 3 (LMCO-2), achieves ∼95% degradation of 100 ppm HCHO within 15 min (0.198 min −1 ). Comprehensive characterizations attribute this superior performance to a Co-induced defect-charge synergy, encompassing the proliferation of vacancy-associated surface oxygen species, enhanced oxygen mobility, improved low-temperature reducibility, a narrowed band gap, and accelerated charge separation. Mechanistic investigations reveal that photogenerated holes (h + ) and singlet oxygen ( 1 O 2 ) act as dominant oxidative species, while superoxide radicals (∙O 2 − ) serve as crucial intermediate precursors. Furthermore, in situ DRIFTS confirms a stepwise oxidation pathway involving dioxymethylene and formate intermediates prior to ultimate mineralization into CO 2 and H 2 O. Graphical Optimized Co substitution endows LaMn 1-x Co x O 3 with enriched oxygen vacancies, a narrowed band gap, and efficient charge separation, enabling h + / 1 O 2 -driven HCHO oxidation with 95% removal within 15 min.