In-Situ Construction of 2D/2D CuCo2S4/Bi2WO6 contact heterojunction as a visible-light-driven fenton-like catalyst with highly efficient charge transfer for highly efficient degradation of tetracycline hydrochloride

The heterogeneous photo-Fenton technology by integrating the merits of photocatalysis and Fenton oxidation is verified to be a promising environmental purification technology due to its relatively mild reaction conditions, low cost and high treatment efficiency. Herein, we demonstrate the fabrication of Type-II CuCo2S4/Bi2WO6 heterojunction as an effective catalyst for the removal of tetracycline hydrochloride (TC-HCl). Two photoactive components are combined to form a two-dimensional/two-dimensional (2D/2D) heterojunction by coupling 2D CuCo2S4 with 2D Bi2WO6 nanosheets, in which CuCo2S4 cocatalyst broadens the light responsive range, facilitates the separation and transfer of photogenerated carriers. Most importantly, CuCo2S4 initiates the photo-Fenton catalysis by utilization photogenerated electrons to react with Cu (II) and Co (III) in presence of hydrogen peroxide (H2O2) to accelerate the circulation of the photo-Fenton reaction. Thus, the generated OH and·O2- are applied as potent free radical species for the catalytic degradation of pollutants. The synthesized CuCo2S4/Bi2WO6 heterostructures exhibited excellent photo-Fenton catalytic activity for TC-HCl removal. The rate constant (kapp/min−1) of 0.5% CuCo2S4/Bi2WO6 heterojunction is about 1.8 times higher than pure Bi2WO6. Recycling experiments show that the catalyst maintained its high activity after being reused for 4 cycles, reflecting its good stability. Meanwhile, hydroxyl radical (·OH) and superoxide radical (·O2-) were identified as oxygen active species, taking a key role in the degradation of TC-HCl. Based on the trapping experiment and energy band analysis, a reasonable photo-Fenton oxidation mechanism for Type-II CuCo2S4/Bi2WO6 heterojunctions is put forward. This work will arouse researchers' enthusiasm for introducing transition metal sulfides as cocatalyst to design heterogeneous photo- Fenton catalyst.