Morphology-Engineered NiV–LDH/CdMoSe Quantum Dot S-Scheme Heterojunctions for LED-Driven H ₂ O ₂ Production and Cr(VI) Reduction

High Resolution Image Download MS PowerPoint Slide Photocatalytic hydrogen peroxide (H 2 O 2 ) is a sustainable alternative approach for the energy-intensive, demanding anthraquinone process, yet suppressing charge recombination under visible light illumination remains a critical bottleneck. Hence, designing a heterostructured photocatalyst is a promising strategy to enhance photocatalytic performance. Herein, we report the interfacially engineered n–n S-scheme heterojunction of CdMoSe QDs with morphologically modified NiV–LDH. The optimized nanocomposites were evaluated for photocatalytic H 2 O 2 production and Cr(VI) detoxification under light-emitting diode (LED) light irradiation. Interestingly, the NiV–LDH nanoflower-modified CdMoSe-QD (CNF) exhibits a greater number of reactive sites, larger interfacial contact area, and enhanced defect density, which collectively promote efficient charge separation and accelerated interfacial carrier migration. As a result, CNF achieves a superior H 2 O 2 production rate of 1658 μmol g –1 h –1 compared with NiV–LDH nanorod-integrated CdMoSe-QD (CNR, 1527 μmol g –1 h –1 ). Additionally, CNF demonstrates remarkable Cr(VI) reduction efficiency of 94.6% and retains excellent stability up to the fifth cycle due to its defect-rich surface that facilitates efficient interfacial charge transfer and suppresses charge recombination. The mechanistic investigations revealed that reactive oxygen species play a crucial role in delaying carrier separation through the formation of an S-scheme heterojunction. The CNF nanocomposite attains a solar-to-chemical conversion efficiency of 1.31% and an apparent quantum yield of 3.25% for photocatalytic H 2 O 2 production. Photoelectrochemical and spectroscopic analyses, including enhanced photocurrent density, quantum confinement effect of CdMoSe-QDs, and delayed charge carrier recombination evidenced by photoluminescence (PL), time-resolved PL, and electrochemical impedance spectroscopy, further substantiate the improved charge transfer mechanism. Moreover, scavenger experiments and ultraviolet photoelectron spectroscopy work-function analysis and Kelvin probe force microscopy measurements provide strong evidence supporting the proposed S-scheme charge transfer mechanism.