Abstract <p>Hematite-reduced graphene oxide (α-Fe₂O₃/rGO) composites are promising platforms for environmental, energy, and sensing technologies. This work investigates the effect of hematite particle synthesis on the morphology, and the physicochemical properties of hydrothermally prepared α-Fe₂O₃/rGO composites. Two approaches were employed: (1) involves sol–gel autocombustion derived hematite nanoparticles, combined with rGO at various relative weight ratios, and (2) iron chloride with varying rGO amounts under the same synthesis conditions. Both routes successfully produced composites, exhibiting fundamentally different morphologies and increased defect density as evidenced by Raman analysis. The first approach yielded two-dimensional network composite, while the second one yielded graphene-wrapped particulate structure. Consequently, both composite types exhibited enhanced UV–visible absorbance and reduced optical bandgap, more pronounced for the iron chloride approach. Electrical conductivity is increased up to 77.89 × 10⁻³ S m⁻¹, while composites from the first route exhibited better Methylene Blue adsorption, underlining morphology-controlled optoelectrical properties and water remediation performance.</p> Impact Statement <p>This study provides a practical design tool for the fabrication of advanced functional material with optimized optoelectrical properties. We have demonstrated that our synthesis method is powerful, since it provides insightful results about how the choice of the starting materials (reagents) either presynthesized nanoparticles or iron salt precursor, does control the final composite morphology, as a result its functional properties. Our work also provides, a clear and actionable roadmap for the scientific community: For instance, for applications requiring efficient pollutant removal, the two-dimensional network-decorated composite is preferred. This composite type is also favored over the other one in the sensing field due to its enhanced electrical conductivity. However, for applications in the photocatalysis field, the graphene-wrapped morphology is more suitable due to its enhanced optical properties, in particular its reduced optical bandgap. Our results are reproducible and offer a complete discussion on the structure-property relationship by establishing a clear correlation between the material’s morphology, interfacial interactions, optical, and electrical behavior.</p> <p>To conclude, our work goes beyond conventional synthesis routes to enable researchers to rationally design versatile materials with tunable properties for specific applications.&#xa0;It also opens new avenues for the development of “innovative” technologies for the engineering material field, to overcome environment, technological, and societal challenges.</p> Graphical abstract <p></p>