Fe-doped SnO2 nanoparticles: enhancing the photocatalytic hydrogen efficiency, Rhodamine-B dye degradation and visible light absorption

Materials for Renewable and Sustainable Energy https://doi.org/10.1007/s40243-024-00288-1 (2025) 14:14 ORIGINAL PAPER Fe-doped SnO2 nanoparticles: enhancing the photocatalytic hydrogen efficiency, Rhodamine-B dye degradation and visible light absorption Aashish K Moses1 · Srinath Ranjan Tripathy1 · Saroj Sundar Baral1 Received: 7 August 2024 / Accepted: 10 December 2024 © The Author(s) 2024 Abstract The existing energy-wastewater nexus may be resolved using metal oxide semiconductor photocatalysts in photocatalytic hydrogen production and pollutant degradation, which is a clean and sustainable process. SnO2 is one such well-researched and proven photocatalyst that is now in use, although it only works with ultraviolet light, which only makes up 4% of the total solar energy received. The present research aims to use iron as a dopant to make SnO2 active under visible light, enhancing reactions like water splitting and dye degradation. The sol-gel method was used to synthesize the photocatalysts. XRD, BET, UV diffuse reflectance spectra, PL spectra, XPS, and SEM micrographs were used to characterize the synthesized photocatalysts. For 7.5 wt% Fe-doped SnO2, a remarkable hydrogen generation rate of 18.81 µmol/hr under sunlight was achieved, nearly three times that of pure SnO2 (5.71 µmol/h). The nanocomposites display excellent photoreactivity towards RhB dye degradation with an optimal concentration of 7.5 wt% Fe-doped SnO2. This optimal composite photocatalyst removes 93% of RhB dye on 0.1 g/L photocatalysts in only 60 min under sunlight. Pristine SnO2 removes 36% of the dye under similar reaction conditions. The photoluminescence spectra of Fe-doped SnO2 had lower peak locations than the pristine SnO2, indicating a decreased rate of charge recombination and increased life duration of the active species. As a result, hydrogen generation rates and dye degradation efficiencies have increased significantly. The photocatalyst’s recyclability study revealed that the photocatalysts can be used efficiently for four cycles without significant reduction in the yield. Keywords Photocatalysis · Hydrogen production · Water splitting · Fe-doped SnO2 · Rhodamine B dye degradation Introduction In recent years, the escalating energy crisis and environmental pollution have sparked immense interest in developing efficient and sustainable technologies for clean energy production and wastewater treatment [1–3]. Photocatalysis, a process that utilizes light energy to initiate chemical reactions, has emerged as a promising avenue to address these pressing challenges [4]. Among various photocatalytic Saroj Sundar Baral Aashish K Moses Srinath Ranjan Tripathy 1 Department of Chemical Engineering, BITS Pilani, K.K.Birla Goa Campus, Goa 403726, India materials, tin dioxide (SnO2) has garnered significant attention due to its excellent photocatalytic properties and natural abundance [5].To enhance the photocatalytic performance of SnO2, the incorporation of transition metal dopants has been widely explored. Iron (Fe), with its unique electronic properties, has demonstrated great potential as a dopant to enhance the photocatalytic activity of SnO2 [6, 7]. The Fe-doped SnO2 photocatalysts combine the inherent advantages of SnO2, such as high stability, low toxicity, and costeffectiveness, with the catalytic properties of Fe, which can improve charge separation and extend the absorption range into the visible light region [8]. This research paper aims to investigate the utilization of Fe-doped SnO2 photocatalysts for two crucial applications: photocatalytic hydrogen production and rhodamine B dye degradation. Photocatalytic hydrogen production is a sustainable and environmentally friendly approach to generating clean energy, while the degradation of organic dyes represents a vital step towards water remediation and pollution control [7, 9]. 13 14 Page 2 of 13 The photocatalytic water splitting reaction mechanism for hydrogen production typically involves three key steps: first, the absorption of light by semiconductor photocatalysts, which generates electron-hole pairs; second, the separation of these charges and their subsequent migration to the surface of the photocatalysts; and third, the surface reactions that occur. In the dye degradation process, the photogenerated electron-hole pairs interact with nearby oxygen and water molecules to produce reactive oxygen species (ROS), effectively breaking down the dye molecules [10, 11]. The photocatalytic hydrogen production using Fedoped SnO2 photocatalysts harnesses solar energy to drive the water-splitting reaction, resulting in the generation of hydrogen fuel [9]. This process holds great promise as a renewable and carbon-neutral alternative to conventional fossil fuel-based energy sources. Incorporating Fe dopants into SnO2 can modify the band structure, enhance the charge carrier mobility, and reduce recombination rates, thereby improving the overall efficiency of hydrogen production [12]. Additionally, the degradation of organic dyes, such as rhodamine B, has become a critical concern due to their widespread use and potential environmental hazards [13]. Fe-doped SnO2 photocatalyst have demonstrated excellent photocatalytic activity for dye degradation owing to their enhanced visible light absorption and efficient electron-hole separation [14]. Understanding the underlying mechanisms of dye degradation using Fe-doped SnO2 will provide valuable insights into developing advanced photocatalytic materials for environmental remediation [13]. This research comprehensively investigates the synthesis, characterization, and performance evaluation of Fe-doped SnO2 photocatalyst for photocatalytic hydrogen production and rhodamine B dye degradation. The experimental results and thorough analysis will shed light on the crucial factors influencing the photocatalytic activity, such as doping concentration, synthesis method, and reaction conditions. Furthermore, the study aims to elucidate the reaction mechanisms involved in these photocatalytic processes, providing a solid foundation for further optimization and scale-up of Fe-doped SnO2 photocatalysts. The novelty of this research lies in using iron as a dopant to activate SnO2 under visible light, significantly enhancing its dual catalytic activity for water splitting and dye degradation. Materials and methods Materials Tin chloride pentahydrate and ferric nitrate were employed as metal precursors. Isopropyl alcohol (C3H8O, 70% V/V, 13 Materials for Renewable and Sustainable Energy (2025) 14:14 Loba Chemie, India) was used as the solvent in the sol-gel procedure. We obtained deionized water from a local labscale distillation unit. Synthesis of SnO2 The sol-gel method was used to synthesise SnO2, where the precursor O.1 M SnCl4.5H2O was dissolved in deionized water and ethylene glycol was added dropwise. A magnetic stirrer was used to agitate the reaction mixture for 30 min at 300 RPM at r (...truncated)