Oxygen vacancy–engineered δ-MnO_x/activated carbon for room-temperature catalytic oxidation of formaldehyde

Although oxygen vacancies (OVs) commonly act as adsorption/active sites in catalytic oxidation of formaldehyde (HCHO), thereby strongly influencing catalyst activity, their control and translation into scale-up products for practical application remain challenging. Herein, δ-MnO_x/activated carbon was synthesized via in situ reduction coupled with ammonia modification, and the developed method was found to allow easy OV control for large-scale production. OV concentration was effectively regulated through adjustment of Mn³⁺ content, and OV roles in the catalytic reaction were probed by several techniques. The optimized catalyst featured superior HCHO removal efficiency and CO₂ selectivity at room temperature, mainly due to oxygen activation by abundant OVs to form reactive oxygen species. The intermediates and pathways of HCHO removal were investigated. Thus, this work provides insights into the enhancement of active site exposure through OV control for a single bulk catalyst and demonstrates its applicability for efficient and commercially viable room-temperature oxidation of HCHO.