Mn2V2O7 Nanocrystals—Investigation of Photocatalytic Efficiency

Purifying wastewater to eliminate harmful organic molecules has been a major focus of both industrial and academic research. Many solutions have been suggested, and one promising approach is to use catalyst materials to break down organic pollutants while they are still in water. This method is cost-effective, environmentally friendly, and efficient at removing contaminants from wastewater. Among catalysts, photocatalysts are particularly interesting because external radiation, such as sunlight, can help the organic compounds degradation.<br/>To assess the photocatalytic potential of β-phase manganese pyrovanadate (Mn₂V₂O₇), we successfully synthesized Mn₂V₂O₇ particles using urea as the precipitating agent in a homogeneous solution. We obtained single-phase β-Mn₂V₂O₇ crystals after heat treatment at 410 °C. A phase transition to α-Mn₂V₂O₇ was observed at 560°C. Morphological analysis revealed that the β-Mn₂V₂O₇ particles have a plate shape formed by smaller crystallites, suggesting a growth mechanism known as "oriented attachment." The band gap energy of β-Mn₂V₂O₇ measured by UV-vis spectroscopy was 4.1 eV. We evaluated the photocatalytic efficiency by studying the degradation of Rhodamine B and Methylene Blue dyes in an aqueous solution under UV radiation. The β-Mn₂V₂O₇ crystals showed low photocatalytic activity, with no degradation observed for the Rhodamine B dye and a 47% degradation of the Methylene Blue dye. The energy used (UV) for activation in the photocatalytic process is close to the band gap energy of the semiconductor, which may make it challenging to generate the electron/hole pair. Additionally, the low photocatalytic efficiency may be due to recombination of the electron/hole pair in the semiconductor/solution interface, preventing the formation of oxidative radicals responsible for photodegradation.