<p>This work investigates the relationship between the concentrations of Fe and Zn in the synthesis of ZnFe₂O₄/α-Fe₂O₃ heterojunction nanoparticles (NPs) and the photocatalytic performance of the resulting Z-scheme photocatalysts. ZnFe₂O₄/α-Fe₂O₃ NPs were prepared by the Pechini-type sol-gel method using different Fe:Zn ratios of 51:49, 57:43, 63:37, and 69:31 in wt% and calcined at 500 °C for 2 h. FT-IR, X-ray diffraction, and Raman analyses confirmed the presence of a mixture of ZnFe₂O₄ and α-Fe₂O₃ phases in all the samples. Morphology analysis revealed that the samples with Fe:Zn ratios of 51:49 and 57:43 wt% comprised semispherical and icosahedral-shaped NPs. In contrast, the samples with Fe:Zn ratios of 63:37 and 69:31 wt% contained semispherical and elongated icosahedral NPs and disc-shaped particles. The energy band structure and alignment of ZnFe₂O₄ and α-Fe₂O₃ formed a type II heterojunction in all the samples. The sample with a Fe:Zn ratio of 69:31 wt% demonstrated the best photocatalytic performance, achieving 84.3% degradation of methylene blue (MB) after 120 min of exposure to natural solar irradiation and exhibiting a higher first-order kinetics constant of 1.36 × 10⁻² min⁻¹. The superior photocatalytic performance was attributed to the higher relative phase content of α-Fe₂O₃, which acts as an electron mediator in the proposed Z-scheme heterojunction mechanism. The scavenger experiments indicated that the primary species responsible for decomposing MB were ·O₂⁻ and ·OH. Finally, the samples demonstrated excellent recyclability and stability over four cycles.</p> Graphical Abstract <p></p>