Controlled Growth of Phase-Pure α-Fe2O3 Nanoparticles on g-C3N4 for the Construction of High-Performance Direct Z-Scheme Heterojunction Photocatalysts

This work presents an innovative two-step approach for constructing efficient direct Z-scheme heterojunction photocatalysts, involving the direct growth of hematite (α-Fe2O3) nanoparticles on graphitic carbon nitride (g-C3N4). The key to this strategy lies in an initial ultrasound-assisted impregnation step that induces the cleavage of g-C3N4 sheets in the presence of FeCl3 precursors while simultaneously promoting the effective anchoring of Fe-N and C-O/C-N species. Interestingly, conversion into hematite nanoparticles is easily achieved in a subsequent short and mild microwave-treatment step, eliminating the need for conventional high-temperature processes. The hematite phase-purity of the nanoparticles, critically controlled by the initial FeCl3 precursor concentration, directly impacts the photocatalytic activity of the g-C3N4@Fe nanohybrid heterojunction. A two-fold enhancement in the photocatalytic degradation of methylene blue compared to α-Fe2O3 and g-C3N4 is achieved for nanohybrids with highest hematite phase-purity. This significant improvement is attributed to the successful formation of a direct Z-scheme g-C3N4/α-Fe2O3 heterojunction photocatalyst as confirmed by electron spin resonance (ESR) analysis. Our two-step approach offers a facile, efficient and scalable route for the development of highly active heterojunction photocatalyst, of promise for the sustainable degradation of contaminants in environmental remediation technologies.