Enhanced oxidative ability, recyclability, water tolerance and aromatic resistance of α-MnO 2 catalyst for room-temperature formaldehyde oxidation via simple oxalic acid treatment.

To obtain a versatile formaldehyde oxidation material, simultaneously increasing the oxidative ability, recyclability and deactivation repellence (e.g., enduring the interference from moisture and aromatic compound omnipresent in indoor air) is of great significance. Herein, the above properties of α-MnO ₂ were synchronously updated via one step treatment in oxalic acid (H ₂ C ₂ O ₄ ), and an in-depth understanding of the surface properties-performance relationship was provided by systematic characterizations and designed experiments. Compared with the pristine sample, XPS, ESR, O ₂ -TPD, CO-TPR and pyridine-IR reveal that H ₂ C ₂ O ₄ created substantial Mn ³⁺ species on surface, exposing a higher coverage of oxygen vacancies that actively participated in the dissociative activation of gas-phase O ₂ into reactive chemically adsorbed oxygen (O _C ), and the abundant Lewis acid sites further enabled the effective O ₂ activation process. The large amount of oxygen O _C promoted the HCHO-to-CO ₂ conversion and inhibited the accumulation of formate that required a high temperature of 170 °C to be eliminated, thus conspicuously improving the α-MnO ₂ 's thermal recovery. The combined H ₂ O-TPD, H ₂ O-preadsorbed CO-TPR, C ₆ H ₆ -TPD and C ₆ H ₆ -preadsorbed CO-TPR investigations shed light on the H ₂ C ₂ O ₄ -induced water and benzene resistance. The notably weakened water and benzene binding strength with the H ₂ C ₂ O ₄ -modified surface together with the unrestrained oxygen O _C accounted for the outstanding anti-deactivation performance.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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