Morphology controlled synthesis of α-Fe2O3-x with benzimidazole-modified Fe-MOFs for enhanced photo-Fenton-like catalysis

Abstract

Intrinsically poor reactivity restricts pure hematite (α-Fe2O3) from practical photo-Fenton-like systems. Surface structure engineering is considered one of effective methods to tune its photo-Fenton-like catalytic performance. Therefore, it is essential to understand how the surface structure of α-Fe2O3-based photocatalysts alters its catalytic activity at the nanoscale. Herein, four α-Fe2O3-x materials with different morphologies (sphere, octahedron, spindle and rod) and controllable oxygen vacancies (OVs) were synthesized with benzimidazole (BIm)-modified Fe-MOFs (MOFs = metal-organic frameworks) as templates using the solvothermal method. The rod-like α-Fe2O3-x was found to exhibit the highest activity for the complete methylene blue (MB) degradation with apparent reaction rate constant k = 0.08 min−1. While apparent reaction rate constants for α-Fe2O3-x with sphere-, octahedron- and spindle-like morphologies are only 0.02, 0.035 and 0.05 min−1, respectively. The enhanced photocatalytic activity can be attributed to the synergy of large surface area, high Fe2+ and OVs concentrations. This is further substantiated by density functional theory (DFT) calculations, which indicates that both Fe2+ and OVs facilitate H2O2 dissociation to produce hydroxyl radicals (·OH) for MB degradation. The present work provides a promising strategy for designing low-cost and efficient α-Fe2O3-based photocatalysts with abundant OVs for photo-Fenton-like catalysis and other energy and environmental applications.