Efficient photocatalytic reduction of aqueous Cr (VI) by MXene-(Ti3C2, Mo4/3C) and Ca2Fe2O5-based nanocomposites

The reduction of highly toxic hexavalent chromium (Cr(VI)) to less toxic trivalent chromium (Cr(III)) in aquatic environments is a critical research topic. Photocatalytic reduction of Cr(VI) is a green and promising approach, and in this study, brownmillerite Ca 2 Fe 2 O 5 (CFO) and MXene-based (Ti 3 C 2 , Mo 4/3 C) nanocomposites were prepared for the photoreduction of Cr(VI) to Cr(III) under simulated sunlight. An electrostatic assembly, as concluded from X-ray photoelectron spectroscopy data, of CFO nanoparticles and MXene nanosheets significantly improved charge separation and enhanced the photocatalytic performance by forming a Schottky junction. Photoluminescence spectra showed a faster electron transfer from MXene to CFO, reducing recombination losses. The nanocomposites achieved 96 % Cr(VI) reduction with a rate constant of k = 0.0577 min −1 in 60 minutes using Ti 3 C 2 -CFO, and 99 % reduction with a rate constant of k = 0.0911 min −1 in 50 minutes using Mo 4/3 C-CFO. This study provides valuable insights into MXene-based photocatalysts for efficient environmental remediation. Photocatalytic reduction mechanism of Cr(VI) using a Ti3C2-Ca 2 Fe 2 O 5 Schottky junction photocatalyst • Tuned Ca 2 Fe 2 O 5 and MXene nanocomposites for enhanced photocatalytic reduction. • Improved charge separation through the formation of Schottky junction. • 96 % and 99 % Cr(VI) reduction using Ti₃C₂-CFO and Mo 4/3 C-CFO nanocomposites. • MXene-based catalysts offer efficient and sustainable water contaminant reduction.