Fabrication of MnCo2O4@WO3 heterostructured nanocomposites with enhanced photocatalytic reduction of Cr(VI) ions under visible light irradiation

Cr (VI) deposition in water and the ground generated by different industrial operations is an urgent concern in environmental treatment because of its carcinogenic effects on people and aquatic life. Heterogeneous photocatalysts are regarded as a crucial pathway to treating wastewater under visible illumination not only on a laboratory level but also on an industrial level, which piqued the interest of researchers. In this study, a new semiconductor nanocomposite of mesoporous WO3 with different MnCo2O4 contents was constructed using a hydrothermal method. The impact of MnCo2O4 amount on structural, morphological, and optical properties was fully investigated. The reduction of toxic Cr(VI) to less venomous Cr(III) was used to examine the photocatalytic activity of the designed nanocomposites under visible light exposure with formic acid as a hole scavenger. XRD, TEM, and XPS examinations revealed the WO3 and MnCo2O4 phases. Tuning of the MnCo2O4 content to 9.0 wt% results in the improvement of visible light absorption, reducing the bandgap energy (Eg) to a minimum of 1.8 eV, and increasing the separation and mobility of the photogenerated charges. This composite can accomplish complete photoreduction of Cr(VI) within 1 h with a high photoreduction rate constant (0.0459 min−1), which was 2.8 folds higher than pure WO3 and can be increased to 0.0765 min−1 by adapting the dose to 2.0 g/L in 45 min, resulting in excellent stability and reusability for five runs. This research provides an inexpensive strategy to synthesize WO3-based nanocomposites with exceptional wastewater remediation capabilities.