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Promoting the charge migration and separation efficiency of Bi2O2CO3 is an appealing strategy to improve its photocatalytic performance. Herein, iodine-intercalated Bi2O2CO3 (I-Bi2O2CO3) nanosheets were prepared with the assistance of solvents containing multiple hydroxyl groups through a facile hydrothermal route. The formation process and mechanism of I-Bi2O2CO3 are illustrated. Notably, the intercalated iodine ions of the Bi2O2CO3 nanosheets could modify the band structure of Bi2O2CO3 and enhance its light response, while also acting as a bridge for efficient charge migration and separation. As a result, the resultant I-Bi2O2CO3 nanosheets exhibited superior photocatalytic performance for phenol degradation, achieving complete phenol removal within 5 h under solar illumination. Furthermore, the reaction rate constant of the I-Bi2O2CO3 nanosheets was ∼18 times that of Bi2O2CO3. We expect this work to bring new insights into the structural regulation of photocatalysts for the efficient separation of charge carriers and enhanced photocatalytic performance. [ABSTRACT FROM AUTHOR]

Normally, the band structure of a photocatalyst can be tuned by surface oxygen vacancies or element doping, however, employing the synergetic effects of surface oxygen vacancies and oxyacid group replacements to regulate the band structure of the photocatalyst is challenging. Here, the band structure of BiOBr nanosheets was regulated by surface oxygen vacancies and VO3− ions replacement through a hydrothermal VO3− ions exchange route, in which the VO3− transform into VO43− for BiVO4 and BiV1.025O4+x. The crystal phase of the products evolved from BiOBr, BiOBr/BiVO4, BiOBr/BiVO4/BiV1.025O4+x, and BiVO4/BiV1.025O4+x accordingly, when gradually increasing the concentration of VO3− (NH4VO3) from 0.05 to 3.0 mmol. In particular, the BiOBr nanosheets with surface oxygen vacancies and VO43− ion replacement (by adding 0.05 mmol of VO3−) possessing defective states and more negative conduction band potential could promote visible-light-driven photocatalytic performances of organic contaminants due to the effective separation of charge carriers. This work provides new insight into refining the band structure of photocatalysts and evidential proof of a phase transition through oxyacid exchange. [ABSTRACT FROM AUTHOR]

In this study, the phase transition from tetragonal BiOBr to monoclinic Bi4O5Br2 was regulated in the presence of branched polyethyleneimine (BPEI) containing massive amino groups via a hydrothermal route. Based on the crystal phase of the products obtained at different concentrations of the BPEI and Br− sources, the relative concentration of BPEI (the concentration ratio of the BPEI and Br− sources, BPEI/Br−) played the decisive role in this phase transition. In particular, a BPEI/Br− value over 0.2 g mmol−1 with excessive BPEI was critical for the phase transition. Further, a reasonable theory referring the synergistic effect of the "drag force" and facet recognition of excessive BPEI underlying this phase transition was confirmed through a series of systematically designed experiments. The protonated amino groups from excessive BPEI could not only act as a "drag force" to extract the bromine ions from the solid-state BiOBr nanosheets but also recognize the (001) facet of BiOBr, thereby distorting the tetragonal structure of the BiOBr nanosheets and forming monoclinic Bi4O5Br2 nanosheets. This work provides a new insight and proof of the regulation of the phase transition of BiOBr to Bi4O5Br2. [ABSTRACT FROM AUTHOR]