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<p>Water can be severely contaminated by the reckless dumping of industrial effluents, which contain organic pollutants such as pharmaceuticals, phenolic compounds, and dyes, with cascading effects on human health and the ecosystem. Remarkably, photocatalysis is a rapidly expanding method for treating a wide range of organic pollutants. Here, the photocatalytic activity of Ag-doped α-Fe<sub>2</sub>O<sub>3</sub> (metal-doped oxide nanocomposites) is compared with that of monolithic catalysts (substrate-based materials), offering an economical, environmentally friendly, efficient, and low-power/sunlight-driven process. The results revealed that the substrate-based catalysts could improve the photodegradation efficiency of as-fabricated nanocomposite photocatalysts. The electrochemical property of 3% Ag: α-Fe<sub>2</sub>O<sub>3</sub>/Ni/Graphene Foam (GF) (optimized catalyst) exhibits smaller over potential (Oxygen Evolution Reaction (OER): 84 mV and Hydrogen Evolution Reaction (HER): 214 mV) with remarkably minimum resistance (OER: 1.3 Ω and HER: 33 Ω) and high Tafel slope due to bubbles formation (OER: 43 mV dec<sup>− 1</sup> and HER: 170 mV dec<sup>− 1</sup>) to achieve 10&#xa0;mA cm<sup>− 2</sup> of current density, indicating efficient charge transfer activity which correlate with the photodegradation performance of photocatalyst. The highest degradation rate against selected organic pollutants was also achieved by optimal 3% silver doping: ciprofloxacin (62% within 70&#xa0;min) &gt; Methyl Orange (59% within 90&#xa0;min) &gt; 2,4-dinitrophenol (DNP with 39% within 120&#xa0;min), representing more complex and stable chemical structures of Methyl Orange (-N = N-) and 2,4-DNP (-NO<sub>2</sub> groups). The degradation process followed a pseudo-first-order kinetic model (R<sup>2</sup> values close to 1) beyond the optimal doping level. Photocatalytic and electrochemical activity decreased due to e<sup>−</sup>-h<sup>+</sup> recombination, decreased surface area, and reduced availability of reactive species. Additionally, the reusability of the optimized monolithic catalyst showed only 2.4, 3.8, and 4.6% decreases in ciprofloxacin, Methyl Orange, and 2,4-DNP, respectively, thus confirming its stability and sustainability as a promising candidate for organic industrial wastewater treatment.</p>

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Comparative performance of hematite-based nanopowder and monolithic photocatalysts on Ni/GF substrates for sunlight-driven degradation of organic contaminants

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月20日

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  • Iqra Mazhar,
  • Muhammad Afzaal,
  • Muhammad Altaf,
  • Manzar Sohail,
  • Raja Shahid Ashraf,
  • Abdul-Sattar Nizami

摘要

Water can be severely contaminated by the reckless dumping of industrial effluents, which contain organic pollutants such as pharmaceuticals, phenolic compounds, and dyes, with cascading effects on human health and the ecosystem. Remarkably, photocatalysis is a rapidly expanding method for treating a wide range of organic pollutants. Here, the photocatalytic activity of Ag-doped α-Fe2O3 (metal-doped oxide nanocomposites) is compared with that of monolithic catalysts (substrate-based materials), offering an economical, environmentally friendly, efficient, and low-power/sunlight-driven process. The results revealed that the substrate-based catalysts could improve the photodegradation efficiency of as-fabricated nanocomposite photocatalysts. The electrochemical property of 3% Ag: α-Fe2O3/Ni/Graphene Foam (GF) (optimized catalyst) exhibits smaller over potential (Oxygen Evolution Reaction (OER): 84 mV and Hydrogen Evolution Reaction (HER): 214 mV) with remarkably minimum resistance (OER: 1.3 Ω and HER: 33 Ω) and high Tafel slope due to bubbles formation (OER: 43 mV dec− 1 and HER: 170 mV dec− 1) to achieve 10 mA cm− 2 of current density, indicating efficient charge transfer activity which correlate with the photodegradation performance of photocatalyst. The highest degradation rate against selected organic pollutants was also achieved by optimal 3% silver doping: ciprofloxacin (62% within 70 min) > Methyl Orange (59% within 90 min) > 2,4-dinitrophenol (DNP with 39% within 120 min), representing more complex and stable chemical structures of Methyl Orange (-N = N-) and 2,4-DNP (-NO2 groups). The degradation process followed a pseudo-first-order kinetic model (R2 values close to 1) beyond the optimal doping level. Photocatalytic and electrochemical activity decreased due to e−-h+ recombination, decreased surface area, and reduced availability of reactive species. Additionally, the reusability of the optimized monolithic catalyst showed only 2.4, 3.8, and 4.6% decreases in ciprofloxacin, Methyl Orange, and 2,4-DNP, respectively, thus confirming its stability and sustainability as a promising candidate for organic industrial wastewater treatment.