The crystal structure of Bi4O5I2 and its relation to the structure of Bi4O5Br2

Elucidating Structural Disorder in Ultra-Thin Bi-Rich Bismuth Oxyhalide Photocatalysts

Advancing the field of photocatalysis requires the elucidation of structural properties that underpin the photocatalytic properties of promising materials. The focus of the present study is layered, Bi-rich bismuth oxyhalides, which are widely studied for photocatalytic applications yet poorly structurally understood, due to high levels of disorder, nano-sized domains, and the large number of structurally similar compounds. By connecting insights from multiple scattering techniques, utilizing electron-, X-ray- and neutron probes, the crystal phase of the synthesized materials is allocated as layered Bi24O31X10 (X = Cl, Br), albeit with significant deviation from the reported 3D crystalline model. The materials comprise anisotropic platelet-shaped crystalline domains, exhibiting significant in-plane ordering in two dimensions but disorder and an ultra-thin morphology in the layer stacking direction. Increased synthesis pH tailored larger, more ordered crystalline domains, leading to longer excited state lifetimes determined via femtosecond transient absorption spectroscopy (fs-TAS). Although this likely contributes to improved photocatalytic properties, assessed via the photooxidation of benzylamine, increasing the overall surface area facilitated the most significant improvement in photocatalytic performance. This study, therefore, enabled both phase allocation and a nuanced discussion of the structure-property relationship for complicated, ultra-thin photocatalysts.

Multifunctional property exploration: Bi4O5I2 with high visible light photocatalytic performance and a large nonlinear optical effect

Exploration of the versatility of materials is very important for increasing the utilization of materials. Herein, we successfully prepared Bi₄O₅I₂ powders via a facile solvothermal method. The Bi₄O₅I₂ photocatalyst exhibited significantly higher photocatalytic activity as compared to the common BiOI photocatalyst in the degradation of methyl orange, methylene blue and rhodamine B under visible light irradiation. Especially, for the degradation of methyl orange, the photocatalytic activity of Bi₄O₅I₂ is about 10 times that of BiOI. Moreover, Bi₄O₅I₂ exhibits an extremely high second harmonic generation response of about 20 × KDP (the benchmark) estimated by the unbiased ab initio calculations. The coexisting multifunction of Bi₄O₅I₂ is mainly because of the increased dipole moment due to the stereochemical activity of lone pairs that promotes separation and transfer of photogenerated carriers, then enhances the photocatalytic activity and results in a high second harmonic generation response. This indicates that Bi₄O₅I₂ may have good potential applications in photocatalytic and nonlinear optical fields.

Bi₄O₅I₂ exhibits an extremely high second harmonic generation response and enhanced photocatalytic activity. The multifunction of Bi₄O₅I₂ is mainly resulting from the dipole moment of the stereochemical activity of Bi 6s lone pairs.

Fe-doped Bi4O5Br2 visible light photocatalyst: A first principles investigation

This study employed first principles calculations to investigate Fe-doped Bi4O5Br2 as a potential photocatalyst with high efficiency. Based on formation energy calculation, the Fe atoms prefer to replace the Bi atoms with coordination bond of 3, and the optimal concentration for Fe-doping is 6.06[Formula: see text]wt.%. From surface energy calculations, the [Formula: see text] surface has the lowest surface energy, and therefore the easiest cleavage facet is [Formula: see text]. The key factors for the improvement of photocatalytic efficiency after Fe-doped Bi4O5Br2 are estimated as follows. First, the band gap decreases from 2.63[Formula: see text]eV in pristine case to 2.40[Formula: see text]eV in 4 Fe-doped Bi4O5Br2 case, resulting in the photon absorption edge shift to lower energy range and the absorption coefficient increase. Secondly, the work functions decrease from 5.66 eV (pristine) to 4.92[Formula: see text]eV (4 Fe-doped Bi4O5Br2), which facilitate the electrons escaping from the surface. Thirdly, the relative mass ratio of photo-induced electrons and holes increases with Fe concentration. Because the Fe 3[Formula: see text] impurity states in the forbidden band gap become wider, the relative ratio increased after Fe-doped Bi4O5Br2. Finally, the Fe doping process introduces more active sites on the surface, which can effectively improve the capacity of target molecules adsorption. Therefore, it is reasonable to believe that Fe-doped Bi4O5Br2 can effectively improve the photocatalytic efficiency because the abovementioned key factors have tremendously improved. Our work provides a reasonable reason for choosing Fe as a dopant, which can help our experimental work and provide explanation for photocatalytic efficiency improvement.

Heavy pnictogen chalcohalides: the synthesis, structure and properties of these rediscovered semiconductors

Heavy pnictogen chalcohalides offer various shades from the same palette, like “Paysage” by Nicolas de Staël. Their versatility and tunability lead to a new world of possible applications.

Synthesis of Bi4O5Br2 from reorganization of BiOBr and its excellent visible light photocatalytic activity

In this study, a novel visible-light-driven Bi₄O₅Br₂ photocatalyst was successfully synthesized via the structure reorganization of BiOBr at room temperature using NH₃·H₂O as a structure-controlling agent.

Synthesis of BiOI/Bi4O5I2/Bi2O2CO3 p–n–p heterojunctions with superior photocatalytic activities

The formation of p–n heterojunctions among BiOI, Bi₄O₅I₂ and Bi₂O₂CO₃ enhances the charge transfer and separation of the photogenerated carriers and photocatalytic activity.

Influence of facets and heterojunctions in photoactive bismuth oxyiodide

An investigation into the influence of facets versus heterojunctions in the photoactivity of bismuth oxyiodide composites.