Abstract
Photocatalysis enables room temperature synthesis of hydrogen peroxide (H2O2) without any byproducts as well as offering advantages such as low cost, and no release of toxic chemicals [1]. Thus, photocatalysis is an appealing approach for the environmentally friendly synthesis of H2O2. Two-dimensional (2D) layered transition metal chalcogenide (TMC) photocatalysts are good at light harvesting due to their high specific surface area and exhibit excellent optoelectronic properties which make them suitable for environmental remediation and energy production [2]. Metal sulfides have a narrower band gap, which improves their light absorption ability in the visible spectrum. However, they often suffer from low quantum yield and high charge recombination rate. Carbonaceous materials have been proven as very effective co-catalysts with semiconductors at increasing their photoactivity and decreasing recombination rate [3]. The present study focusses on indium sulfide (In2S3) and its composites with carbon nano tubes (CNTs) and carbon quantum dots (CQDs) for H2O2 generation via two-electron oxygen reduction reaction. In2S3, In2S3-CNT and In2S3-CQD are synthesized via hydrothermal method. Structural and optical properties characterized using several techniques such as XRD, Raman, UV-Vis-DRS, PL spectra, SEM, TEM etc. show high crystallinity of In2S3 lattice, good dispersion of carbons on In2S3 lattice, improved light absorption and decrease in recombination rate in In2S3 carbon composites. Photoelectric properties are studied using chronoamperometry, EIS, cyclic voltammetry etc. The In2S3 carbon composites show good stability and lower charge transfer resistance and higher active surface area than pure In2S3. The carbon composite materials show a significantly higher performance than the pure In2S3. In2S3-CQD achieves H2O2 production rate of 634 µM h-1, which is ~ 17 times higher than that of pure In2S3. These composites also show good performance for water treatment with In2S3-CQD removing 93% chromium(VI) and 94% rhodamine B (RhB) from contaminated water upon 2h of irradiation. The mechanism of removal of the impurities is also discussed. In2S3-CQD has shown good results owing to their good light absorption, high specific surface area, and CQDs being able to act as electron reservoir.
Keywords: Photocatalysis, Hydrogen peroxide photosynthesis, Advanced Oxidation processes, Wastewater Treatment.
References
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