Efficient reduction of cr(VI) over nitrogen defected 1D/2D CuO/g-C₃N₄ heterojunction photocatalysts

The novel 1D/2D CuO/g-C₃N₄ binary heterojunctions with some nitrogen defects were successfully designed and constructed using a simple secondary calcination and wet precipitation method for the first time in the paper. The prepared specific samples were characterized by SEM, TEM-EDX, XRD, UV-vis DRS, XPS, N₂ adsorption-desorption isotherms, TRPL, PL emission spectra, EIS and EPR techniques. The 1D CuO nanowires (CNWs) can uniformly dispersed on the 2D g-C₃N₄ nanosheets resulting in the formation of some nitrogen defects. The lowest band gap energy of 1.75 eV and average lifetime τ_ave of 4.69 ns for the formed 1D/2D 20% CNWs/g-C₃N₄ photocatalyst can be obtained. It can efficiently compel the Cr(VI) reduction rate of 99.92% for the 90 min under simulated visible light by the synergistic effect of formed nitrogen defects and generated electrons (e⁻) and superoxide radicals (•O₂⁻) by a S-scheme mechanism according to the free radical trapping experiments and EPR results, which is 2.79 and 3.44 times higher than that of the 2D g-C₃N₄ nanosheets and 1D CuO nanowires. The 1D/2D 20% CNWs/g-C₃N₄ photocatalyst also showed high catalytic stability with a slight drop of 4.79% in the four repeated use without any change in the structure and morphology based on the XRD and SEM results. The method in this paper can provide a valuable reference and potential promising photocatalysts for the treatment of industrial Cr(VI) containing wastewater.