Fabrication of α-Fe₂O₃ Nanoparticles/g-C₃N₄ Direct Z-Scheme Heterojunction of Durable Photocatalytic Activity

The fabrication of a nanohybrid photocatalyst that combines α-Fe₂O₃ nanoparticles with graphitic carbon nitride (g-C₃N₄) is reported. The ensuing direct Z-scheme heterojunction greatly boosts the photocatalytic activity of the α-Fe₂O₃/g-C₃N₄ nanohybrids. This results in organic dye degradation rates more than two times higher than its individual components, promoted by the efficient charge separation and transfer of the Z-scheme heterojunction mechanism of the nanohybrid photocatalyst. In addition, recyclability tests show an outstanding stability of the nanohybrids spanning five consecutive dye degradation experiments, during which the degradation rate is slightly improved. The origin of the improved photocatalytic performance of the nanohybrid lies in the intimate interaction between α-Fe₂O₃ and g-C₃N₄ afforded by the two-step fabrication process, which enables the direct and controlled growth of α-Fe₂O₃ nanoparticles on g-C₃N₄. A first ultrasound impregnation step promotes the effective anchoring of stable Fe species via Fe-N and C-N/C-O bonding, while a second microwave phase conversion step induces the subsequent growth of α-Fe₂O₃ nanoparticles on the g-C₃N₄ sheets. Careful control of the FeCl₃ precursor concentration up to a threshold value of 0.25 M during impregnation enables complete control over their size and phase. This approach clearly highlights the benefits of microwave reactor systems in the fabrication of hematite-based Z-scheme photocatalytic, overcoming the limitations of conventional thermal treatment technology.