A novel S-scheme heterojunction of MnCo2O4/CeO2 photocatalysts for effective and fast removal of Cr(VI) ion under visible illumination

The Cr(VI) ions' pollution is the most common in anthropogenic activities and drinking water sources. The photocatalytic reduction approach has been considered a promising process and highly desirable for decontamination of Cr(VI)- polluted water. In this contribution, a series of MnCo2O4/CeO2 nanocomposites were constructed for Cr(VI) photoreduction under visible light illumination. The physicochemical characterizations revealed that the 12 wt% MnCo2O4/CeO2 heterojunction photocatalyst exhibited the maximum visible light photocatalytic Cr(VI) reduction efficiency of 100 % within 45 min. Moreover, a photoreduction rate of ⁓7.071 mmol g−1min−1 was achieved at 12 wt% MnCo2O4/CeO2 photocatalyst which was 3.32 times higher than the sole CeO2 nanoparticles (NPs) (2.132 mmol g−1min−1). The heterojunction of MnCo2O4/CeO2 photocatalyst with outstanding photocatalytic ability was maintained after five runs, which verified its superior candidate for efficient and ultrafast removal of Cr(VI) ions. The superb photocatalytic reduction ability was attributed to uniform morphology with well-dispersed MnCo2O4 on the CeO2 NPs, and mesostructured characteristics. In addition, the enhanced photoreduction rate was credited to the construction of S-scheme heterojunction of MnCo2O4/CeO2, which could significantly be transferred and separate photoinduced charge carriers, thus minimizing the photocarrier recombination. This work illustrates the idea of fabricating S-scheme heterojunction nanocomposites and enhancing photocatalytic performance under visible illumination.