Tungsten doped manganese dioxide for efficient removal of gaseous formaldehyde at ambient temperatures

Room-temperature active catalysts are very important to combat against ubiquitous indoor HCHO pollution. Here, tungsten doped MnO 2 (W-MnO 2 ) was first synthesized and investigated for HCHO decomposition at ambient temperature. With addition of WCl 6 as precursor into the mixture of permanganate and manganese chloride, tungsten-doped δ-MnO 2 with weak crystallinity and large specific surface area (>230   m 2 /g) was synthesized. Substitution of W 6+ for Mn in MnO 6 groups reduced the chemical valence of Mn and made adsorbed surface oxygen species more active. As a result, the W-MnO 2 catalyst with the nominal W/Mn ratio achieved efficient and stable activity for real-level indoor HCHO (0.3   mg/m 3 ) under the GHSV as high as 600   L/g cat ·h, the removal efficiency reaching 90% at 30   °C and 60% at 5   °C, respectively.