2D Zinc Sulfoselenides as Photocatalysts for Enhanced Hydrogen Peroxide Production with DFT Analysis

Hydrogen peroxide (H₂O₂) is a crucial chemical in various industries due to its strong oxidizing capabilities, high energy density, and clean decomposition into oxygen and water[1]. However, the conventional anthraquinone process for producing H₂O₂ is energy-intensive and results in toxic by-products, spurring the search for more sustainable alternatives[2]. Among these, photocatalysis has gained attention as an eco-friendly method, leveraging sunlight and water to produce H₂O₂ without generating harmful by-products or requiring significant energy input[3]. Two-dimensional (2D) layered transition metal chalcogenide (TMC) photocatalysts are promising candidates for such applications due to their excellent light-harvesting abilities, large surface area, and favorable optoelectronic properties[4]. In particular, transition metal sulfoselenides (MS_xSe_1-x) are emerging as novel materials due to their tunable properties and low charge transfer resistance, making them highly efficient for photocatalytic processes[5]. In this study, we developed and tuned zinc sulfoselenides (ZnS_xSe_1-x) via a facile hydrothermal process, demonstrating superior H₂O₂ production compared to pure ZnS and ZnSe. Specifically, ZnS_0.5Se_0.5 achieved the highest H₂O₂ production rate of 415 µM h^-1, outperforming ZnS (166 µM h^-1) and ZnSe (262 µM h^-1). The synthesized catalysts were characterized using X-ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, and transmission electron microscopy (TEM). These zinc sulfoselenides exhibited a homogenous morphology, enhanced charge transport, and a higher number of active sites, contributing to their improved photocatalytic performance. To further explore the reaction mechanism, radical scavenger studies were conducted alongside Mott-Schottky analysis and density functional theory (DFT) simulations. DFT calculations revealed favorable energetics for oxygen reduction to H₂O₂ on the distorted ZnS_0.5Se_0.5 (110) surface, which showed strong interactions with O₂ (Eb = -170 kJ/mol) and hydrogen atoms (Eb = -56 kJ/mol). These results highlight the importance of material modification in optimizing photocatalytic performance. By combining experimental results with theoretical insights, this research advances our understanding of the mechanisms behind H₂O₂ production on zinc sulfoselenides and paves the way for the development of more sustainable photocatalytic technologies for industrial applications.<br/>References:<br/>[1] R.L. Myers, The 100 Most Important Chemical Compounds: A Reference Guide, Bloomsbury Publishing USA, 2007.<br/>[2] H. Hou, X. Zeng, X. Zhang, Production of Hydrogen Peroxide by Photocatalytic Processes, Angewandte Chemie International Edition. 59 (2020) 17356–17376. https://doi.org/10.1002/anie.201911609.<br/>[3] Y.C. Zhang, J. Li, M. Zhang, D.D. Dionysiou, Size-tunable hydrothermal synthesis of SnS₂ nanocrystals with high performance in visible light-driven photocatalytic reduction of aqueous Cr(VI), Environ Sci Technol. 45 (2011) 9324–9331. https://doi.org/10.1021/es202012b.<br/>[4] Adabala, S.; Dutta, D. P. A review on recent advances in metal chalcogenide-based photocatalysts for CO2 reduction. J. Environ. Chem. Eng. 2022, 10, 107763.<br/>[5] J. Zhang, M. Wu, Z. Shi, M. Jiang, W. Jian, Z. Xiao, J. Li, C. Lee, J. Xu, Composition and Interface Engineering of Alloyed MoS_2x Se_2(1– _x) Nanotubes for Enhanced Hydrogen Evolution Reaction Activity, Small. 12 (2016) 4379–4385. https://doi.org/10.1002/smll.201601496.