MnO_2基材料常温催化降解甲醛研究进展

甲醛(HCHO)是室内空气中的主要污染物之一,已被世界卫生组织确定为致癌和致畸形物质,对人体健康构成了极大威胁。常温催化技术在室温下即可将甲醛降解为无毒无害的CO_2和H2O,能耗低,具有较好的应用前景。二氧化锰(MnO_2)具有价格低廉、环境友好等优势,且晶型种类多,表现出优异的甲醛催化性能,具有较大的实际应用价值而被广泛研究。本文综述了MnO_2基催化剂,包括离子掺杂MnO_2、MnO_2固溶体和负载型MnO_2的甲醛催化活性及其制备方法,并探讨了其活性影响因素、常温催化反应机理,分析了其研究现状及发展趋势。

Research progress on room-temperature catalytic degradation of formaldehyde over MnO2-based catalysts

Background, aim, and scope Formaldehyde (HCHO), a potential carcinogen, usually exists at high concentration in indoor air, which poses a serious threat on human health. Therefore, it is essential to explore efficient methods to remove formaldehyde. The catalytic technologies for formaldehyde removal at room temperature can fully degrade formaldehyde with low energy consumption. It is the most promising method to remove indoor formaldehyde. The valence state of Mn element ranges from +2 to +7, and MnO₂ possesses four different crystal phases consisting of unique MnO₆] octahedral structure, which allows MnO₂-based materials to have excellent low-temperature redox ability. Thus, MnO₂-based materials are the most promising catalysts to degrade HCHO of low concentration at room temperature. It is of great practical significance to review the application of MnO₂-based materials in the catalytical degradation of formaldehyde at room temperature. In this paper, the structure-activity relationship of doped MnO₂, MnO₂ composites and supported MnO₂ at room temperature were discussed in terms of formaldehyde degradation. And the potential application of MnO₂-based materials in the degradation of formaldehyde at room temperature was also discussed. Materials and methods A total of 63 articles were retrieved by WOS (Web of Science) retrieval TS= (HCHO* AND MnO₂) from all databases before 2019-04-03, and more relevant literatures were found through the references, similar literatures and cited literatures of these articles. And the factors affecting the catalytic activity of MnO₂-based materials for HCHO degradation at room temperature and the corresponding catalytic mechanism were summarized based on these articles. The potential research areas for the catalytic removal of formaldehyde at ambient temperature were proposed. Results</i> Among the formaldehyde catalytic materials, the precious metal-based catalysts can convert formaldehyde of high concentration into CO₂ and H₂O at room temperature, while the MnO₂-based materials of the transition metal oxide-based catalysts are abundant and have showed excellent activity for HCHO of low concentration at room temperature. The actual concentration of HCHO in indoor air is relatively low. Discussion At present, more attentions are focused on noble metal materials to remove HCHO at room temperature. However, the precious metal-based catalyst is very expensive, sintering easily and not convenient for industrial application, while MnO₂-based materials possess special structures and strong redox ability. It is most likely to replace precious metals to degrade formaldehyde of low concentration at room temperature. However, the relationship between the activity and structure of MnO₂-based materials in formaldehyde catalysis at room temperature, and its practical application have been rarely reviewed. Conclusions Supported- MnO₂ is expected to completely degrade formaldehyde of low concentration and does have great application prospect in the field of indoor air purification. Recommendations and perspectives (1) MnO₂-based materials combined with AC, PET, ACF and other materials may be more effective and suitable to remove formaldehyde at low concentration in indoor air; (2) The room temperature catalytic activity of MnO₂-based materials for formaldehyde at low concentration in some complex environments with high humidity and other VOCs pollutants still needs to be further investigated.