Theoretical Guidance for the Construction of Electron-Rich Reaction Microcenters on C–O–Fe Bridges for Enhanced Fenton-like Degradation of Tetracycline Hydrochloride

The construction of dual electron reaction centers is an attractive strategy to accelerate the rate-limiting step in Fenton-like catalyst. In this work, we constructed the dual electron reaction centers and electron transport path over C-O-Fe bridges connected by graphene oxide (GO) and Fe3O4 through density functional theory (DFT). The calculations show that there is a strong interaction of C-O-Fe between GO and Fe3O4, and electrons around C would transfer to Fe along C-O-Fe linkages and the electron-rich reaction microcenters are generated around Fe. Based on it, Fenton-like catalyst of ultra-small Fe3O4 (less than 10 nm) loaded on 3D reduced graphene oxide (rGO) (composite denoted as rGF) was successfully prepared. Characterization analyses have demonstrated that C-O-Fe bonds exist in rGF and CV test confirmed the cross-linked structure implemented by C-O-Fe is thermodynamically beneficial for electrons transport to Fe which is responsible for the regeneration of Fe(II). When the weight ratios of GO to Fe3O4 reach 5%, rGF-5, the optimized composite displays superior Fenton-like performance that the removal efficiencies of tetracycline hydrochloride (TCH) are 98.7% within 60 min and 96.1% within 90 min, with the initial pH 4.5 and pH 6.7, respectively. The excellent cyclic stability of rGF-5 further verifies the structure of electron-rich reaction microcenters on C-O-Fe bond bridges is well established to ensure that Fenton-like reactions continue to occur efficiently. The results of mass spectrometry indicate that products with m/z = 114 converted from TCH (m/z = 445) accounted for 87% at 60 min. This work not only achieves a way to construct high-performance heterogeneous Fenton-like catalysts for degradation of antibiotics, but also provides a new insight for designing various efficient catalysts based on the theoretical guidance.