Preparation of S-type heterojunction N-C3N4/BiOClxI1−x with internal electric field and enhanced photocatalytic properties
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Abstract
N doped carbon nitride (N-C3N4)/BiOClxI1−x S-type heterojunctions were prepared by a facile one-step hydrothermal method. The crystal form, morphology, structure, elemental composition, surface functional groups and optical properties of the samples were characterized by XRD, XPS, SEM, TEM, FTIR and UV-Vis. The photocatalytic activity of N-C3N4/BiOClxI1−x oxidation of organic pollutants and reduction of Cr(VI) was investigated. The results show that N-C3N4/BiOClxI1−x sample exhibits the effective enhancement in light absorption. The charge carriers were generated by the transfer of the photoinduced electron from N-C3N4 to BiOClxI1−x across the interface under irradiation, which inhibited the recombination of electron-hole pairs. Under visible light irradiation, 20%N-BiOCl0.5I0.5 exhibited high activity, the degradation rate of phenol reached 98.53% with 2.5 h of visible light irradiation. Meanwhile, the reduction rate of Cr(VI) of 20%N-BiOCl0.5I0.5 reached to 99.11% with 1 h of visible light irradiation. 20%N-BiOCl0.5I0.5 showed good stability after five cycles. The total organic carbon (TOC) removal rate of degradation phenol by 20%N-BiOCl0.5I0.5 within 3 h was 80.21%. Combined with capture experiment, ESR and DFT calculation, the improvement activity of N-C3N4/BiOClxI1−x was attributed to the formation of S-type heterojunction, the internal electric field based on different Fermi levels between N-C3N4 and BiOClxI1−x, as well as band bending and Coulomb force, which together accelerated spatial separation of photogenerated carriers and orderly electron flow.
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