Orange peel − derived CoFe₂O₄ spinel: A sustainable nanocatalyst for dye removal, water splitting, and CO₂ reduction

The pressing need for sustainable and eco−friendly solutions has driven a paradigm shift towards innovative materials to tackle critical environmental and energy challenges. This study pioneers a green, waste−to−resource methodology for synthesizing cobalt ferrite (CoFe₂O₄) spinel nanoparticles, leveraging orange peel powder as a natural reducing and stabilizing agent. By transforming agro−industrial waste into high−performance nanomaterials, this work exemplifies the seamless integration of circular economy principles with cutting−edge nanotechnology. Comprehensive characterization by XRD, SEM−TEM, BET, and UV−Vis spectroscopy revealed a well−defined cubic spinel structure with an optical bandgap of 1.46 eV, optimized for visible−light absorption. Advanced techniques, including Raman, XPS, and FTIR, uncovered a partially inverted spinel configuration, with Co 2+ and Fe 3+ ions distributed across tetrahedral and octahedral sites. The CoFe₂O₄ nanoparticles demonstrated exceptional multifunctionality, excelling in both environmental remediation and renewable energy applications. In water treatment, the nanoparticles achieved remarkable dye removal efficiencies of 83.49% for malachite green (MG) and 49.73% for methylene blue (MB) through a synergistic adsorption−photocatalysis mechanism under visible light. In visible light−driven energy production, they facilitated hydrogen evolution (480 μ mol/g) and formic acid (180 μ mol/g) production from H 2 O and CO 2 reduction, respectively. These achievements underscore the superior performance of the material compared to conventional photocatalysts. This approach establishes an efficient and sustainable route for nanomaterial synthesis, positioning orange peel−derived CoFe₂O₄ as a promising candidate for large−scale applications in water purification, renewable energy conversion, and carbon capture. By combining eco−compatibility with high catalytic efficiency, this study provides a scientifically grounded framework for advancing green nanotechnology. • Green synthesis of CoFe₂O₄ nanoparticles using orange peel waste as a natural fuel and complexing agent. • Eco-friendly route solely on water, metal salts, and orange peel powder, without auxiliary reagents. • Orange peel promotes CoFe₂O₄ spinel, whereas urea fails to produce the ternary oxide phase. • Efficient removal of synthetic dyes via combined adsorption and visible-light photocatalysis. • Photocatalytic hydrogen evolution and CO₂ reduction to formic acid achieved without sacrificial agents.