for complete oxidation of indoor formaldehyde at room temperature
Formaldehyde, produced mainly from decorating materials, is an indoor air pollutant. Being a carcinogenic substance, it has adverse effects on human health and the environment at large. Due to the continuous awareness and campaigns regarding pollution and the urgent need to curb environmental pollution, the removal of indoor formaldehyde is highly desirable to protect both human health and meet the set environmental regulations. Formaldehyde can be removed from the air by conversion into harmless carbon dioxide and water through complete catalytic oxidation. Currently, noble metal and transition metal oxide catalysts are widely used for catalytic oxidation of formaldehyde. However, these catalysts generally require high reaction temperatures that are not cost-effective. Recently, Pd/ceria catalysts pretreated using non-thermal plasma have been identified as promising catalysts for complete oxidation of formaldehyde at room temperature. This can be attributed to their high-performance due to the interaction between the palladium and cerium oxides.
Non-thermal plasma consists of all the active species required for the preparation and treatment of catalysts, thus allows for efficient and controlled production of structures. Additionally, due to its low gas- and high electron temperature characteristics, non-thermal plasma treatments can prevent agglomeration and sintering of catalysts associated with high calcination temperatures. Equipped with this knowledge, a team of researchers at Sun Yat-sen University: Professor Haibao Huang, Dr. Kai Li and Dr. Jian Ji, investigated the efficient activation of Pd/ceria catalysts using non-thermal plasma to achieve complete catalytic oxidation of indoor formaldehyde at room temperature. Also, the physiochemical properties of the Pd/ceria catalysts were explored using various characterization methods, including in situ DRIFY and X-ray diffraction. Their work is currently published in the research journal, Chemosphere.
The research team observed that unlike the R300 sample, non-thermal activated sample exhibited remarkably high activity and stability due to narrower particle size distribution, smaller palladium particle size, and numerous active surface oxygen species. The performance of the non-thermal activated Pd/ceria catalyst was compared to that of conventional reduced sample for a 300 min formaldehyde conversion test. Results showed for Pd/ceria catalyst, the conversion of formaldehyde to carbon dioxide was kept over 80% at a concentration of 100 ppm and a space velocity of 150000 mL/g/h during the entire test duration. However, the formaldehyde conversion dropped from 70% to 50% in the case of the conventional thermally activated sample because the palladium particles were partially covered by ceria layer, thus blocking oxygen activation and mobility abilities. Moreover, in situ DRIFT characterization revealed that the presence of water significantly increased the formaldehyde conversion into carbon dioxide, mainly because the Pd/ceria catalysts intermediates consisted of formate, polyoxymethylene and dioxymethylene species.
In summary, the study presented non-thermal plasma-activated Pd/ceria catalyst for complete oxidation of indoor formaldehyde at room temperature. The prepared sample exhibited remarkably high-performance over the conventional thermal reduced sample. In a statement to Advances in Engineering, Professor Haibao Huang, the corresponding author said that their study results would enable efficient and complete conversion of formaldehyde into harmless carbon dioxide, thus contributing towards a greener and sustainable environment protection.
Li, K., Ji, J., Huang, H., & He, M. (2020). Efficient activation of Pd/CeO2 catalyst by non-thermal plasma for complete oxidation of indoor formaldehyde at room temperature. Chemosphere, 246, 125762.