Photocatalytic oxidation of formaldehyde under visible light using BiVO4-TiO2 synthesized via ultrasonic blending.

Formaldehyde (HCHO) is one of the primary indoor air pollutants, and efficiently eliminating it, especially at low concentrations, remains challenging. In this study, BiVO4-TiO2 catalyst was developed using ultrasonic blending technology for the photocatalytic oxidation of low-level indoor HCHO. The crystal structure, surface morphology, element distribution, and active oxidation species of the catalyst were examined using XRD, SEM, TEM, UV-Vis, EDS, and ESR techniques. Our results demonstrated that the BiVO4-TiO2 catalyst, prepared by ultrasonic blending, exhibited good oxidation performance and stability. The HCHO concentration reduced from 1.050 to 0.030 mg/m3 within 48 h, achieving a removal rate of 97.1%. The synergy between BiVO4 and TiO2 enhanced the efficiency of separating photogenerated carriers and minimized the likelihood of recombination between photogenerated electrons and holes. Additionally, this synergy significantly enhanced the presence of hydroxyl radicals (·OH) on the catalyst, resulting in an oxidation performance superior to that of either BiVO4 or TiO2. Our research offers valuable insights for the development of new photocatalysts to address HCHO pollution.

Synergistic effect of photo-thermal oxidation for a low concentration of HCHO over Bi3+-TiO2/MnFeOx catalysts at ambient temperature.

Formaldehyde (HCHO) has been one of the important air pollutants, and the effective removal of HCHO at ambient temperature has been a big challenge. In this work, the synergistic effect of photo-thermal oxidation with Bi3+-TiO2/MnFeOx for a low concentration of HCHO was investigated. MnFeOx was synthesized by the complexation method (CM) and co-precipitation (CP), and TiO2 with Bi3+ doping supported on MnFeOx was prepared by using the hydrothermal method to obtain a higher oxidation performance. The results demonstrated an excellent oxidation activity of MnFeOx (CM) for HCHO at ambient temperature, attributed to the morphology effect (large surface areas and small crystal sizes), the large absorption of oxygen, and the interaction and oxygen vacancy formed between MnO2 and FeOx. Although Bi3+-TiO2/MnFeOx showed a similar result as MnFeOx at 48 h, the oxidation activities for HCHO were improved prominently under photo-thermal oxidation at 12 h. The improvement was ascribed to the synergistic effect of Bi3+-TiO2 and MnFeOx with surface adsorbed oxygen, and more generated reactive oxygen species on the surface. In particular, 2 wt% Bi3+-TiO2/MnFeOx displayed the highest activity (90.2%) and good stability (5 cycles), and the HCHO average conversion was increased from 46.2 to 58.2% at 12 h. The feasible oxidation mechanism and reaction pathway were also interpreted. This work provides a new insight for the development of photocatalysts supported on transition metal oxides to oxidize HCHO at ambient temperature.