Bismuth Oxyiodide Microspheres Research Articles

Solvent-mediated synthesis of BiOI with a tunable surface structure for effective visible light active photocatalytic removal of Cr(VI) from wastewater

The present study investigated the effect of various solvents on the tunable surface morphology and photocatalytic activity (PCA) of bismuth oxyiodide (BiOI), which could be used for the reduction of Cr(VI) under visible light irradiation (VLI). BiOI samples exhibiting different morphologies, i.e., two-dimensional square-like nanosheet and three-dimensional hierarchical flower-like morphology, were synthesized by a hydro/solvothermal process using different solvents, namely H2O, MeOH, EtOH, and ethylene glycol (EG). The crystal structure, surface morphology, surface area, light-absorption capability, and recombination rate of the photogenerated charge carriers were examined by X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller analysis, UV–vis diffuse reflectance spectroscopy, photoluminescence, and transient photocurrent analyses, respectively. The BiOI sample fabricated in EG showed excellent photocatalytic efficiency (~99%) for the reduction of Cr(VI) after 90 min under VLI. The enhanced PCA demonstrated that the high surface area and well-structured surface characteristics of flower-like 3D BiOI microspheres played important roles in the photoreduction process. Moreover, a plausible mechanism for the reduction of Cr(VI) over the EG–BiOI photocatalyst was proposed. The results of the PCA evaluation and recycle test revealed that 3D EG–BiOI microspheres could serve as promising materials for the efficient removal of Cr(VI) from wastewater. Additionally, EG–BiOI could be utilized in other environmental remediation processes.

Visible light-driven photoelectrochemical ampicillin aptasensor based on an artificial Z-scheme constructed from Ru(bpy)32+-sensitized BiOI microspheres

Dye sensitization is an alternative strategy to improve photoelectric activity of semiconductors and, particularly, to enhance the activity towards visible light domain. Herein, an artificial Z-scheme bipyridine ruthenium (Ru(bpy)32+) sensitizing narrow-gap bismuth oxy-iodide (BiOI) microspheres was constructed by a simple electrostatic interaction strategy for the first time. The electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) analysis showed that this design of such Z-scheme structure was helpful to enhance the interfacial charge transfer and improve the photoelectric conversion efficiency. In addition, due to the sensitization of Ru(bpy)32+, the band gap was narrowed from 1.8 eV of BiOI microspheres to 1.3 eV of BiOI/Ru(bpy)32+ microspheres, leading to improve the utilization of visible light. So that, the photocurrent of the resulted BiOI/Ru(bpy)32+ was 13.0 times that of pure BiOI microspheres. In view of the outstanding photoelectrochemical (PEC) performance of BiOI/Ru(bpy)32+ and the high specificity of the aptamer, the PEC aptasensor for ampicillin (AMP) merits the excellent detection performance including a broad linear ranging from 1 × 10–7 nM to 100 nM as well as a low detection limit of 3.3 × 10–8 nM (S/N = 3). This work not only provides a novel way to construct and design highly efficient photoactive materials for PEC detection, but also broadens the application of Z-scheme in the field of sensing.

Fabrication of direct Z-scheme Co3O4/BiOI for ibuprofen and trimethoprim degradation under visible light irradiation

The escalation of pharmaceutical products development and sales in the last few decades have raised concerns about their effect on the environment, particularly water and consequently their removal from wastewater. Composites of cobalt oxide (Co3O4) and bismuth oxyiodide (BiOI) were synthesised and evaluated for degradation of ibuprofen (IBU) and effect of trimethoprim (TMP) under visible light irradiation. The properties of the as synthesised composites were evaluated using different techniques such as FTIR, SEM, TEM, XRD, BET, TGA, UV–Vis and PL. The self-assembled direct Z-scheme heterojunction showed high photocatalytic activity for degradation of ibuprofen (97.02%) after adding 2 mg of TMP. TOC reduction of 85.68 ± 2.22% at pH 11.3 was also calculated. The enhanced photocatalytic activity of the Z-scheme heterojunction was attributed to strong visible light absorption properties of the catalyst and improved separation of photoexcited charge carriers resulting from the built-in electric field formed between the BiOI microspheres and the Co3O4 wormy epitaxy established after equilibrium Fermi level was reached. The Z-scheme heterojunction is a promising material for the removal of pharmaceuticals in aquatic effluents.

Ultrathin-Layer Structure of BiOI Microspheres Decorated on N-Doped Biochar With Efficient Photocatalytic Activity.

Bismuth oxyiodide (BiOI) is among the most potential photocatalysts due to its photocatalytic activity under visible light irradiation. However, the photoinduced carrier separation efficiency has limited the BiOI photocatalytic activity. Herein, we utilized the direct carbonation of sapless cattail grass to obtain N-doped hierarchical structure cattail-based carbon (NCC). The NCC not only served as an appropriate host but also as a self-sacrificing template for BiOI microspheres for the preparation of BiOI/NCC composite material. The acidic solutions (HCl or AcOH) were used as a solvent which helped to obtain a well-defined micro/nano hierarchical BiOI microspheres composed of ultrathin nanosheets. Thus, BiOI/NCC composites were successfully designed through the in-situ self-template rapid dissolution-recrystallization mechanism. Additionally, numerous well-contacted interfaces were formed between NCC and BiOI, which served as an electron-acceptor bridge function for ultrafast electron transfer process in order to hinder the electron-hole pairs recombination. On account of the multiple synergistic effects of micro/nano hierarchical microsphere structure, ultrathin nanosheets, and well-contacted interface, the as-prepared BiOI/NCC composites exhibit the superior degradation of rhodamine B (RhB) than pure BiOI under visible light irradiation.

Facile Preparation and Characterization of Nanostructured BiOI microspheres with certain adsorption-photocatalytic properties

A novel adsorbent based nanostructured bismuth oxyiodide (BiOI) microspheres combining the highly effective adsorption and green photocatalytic regeneration were fabricated by a facile and rapid low-temperature chemical bath method. The resultant products were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Nitrogen adsorption-desorption measurements, and UV-Vis diffuse reflectance spectroscopy (DRS). The BiOI microspheres displayed remarkable performance towards removal of Rhodamine B (RhB) and Cr (VI) from aqueous solution, showing a maximum adsorption capacity reached up to 40.78 mg g-1 and 38.01 mg g-1, respectively. The kinetics and equilibrium of adsorption process were found to follow the pseudo-second-order kinetic and Langmuir isotherm models. Notably, the BiOI microspheres have excellent photocatalytic regeneration capability due to their intrinsically prominent photoresponse in visible light region. By meaning of providing a new insight into the design of new generation adsorbent that could combine adsorption and solar-driven photocatalysis, the synthesized BiOI microspheres are very promising for the large-scale industrial application for water treatment.

Synthesis and characterization of BiOI microspheres under standardized conditions

Bismuth oxyiodide (BiOI) has received much attention in the design of materials, because this material has proved its potential application in heterogeneous photocatalysis for environmental decontamination processes using visible light or simulated solar radiation. In this study, standard conditions and a reproducible method of solvothermal synthesis are established in order to obtain BiOI microspheres with higher photocatalytic activity in the degradation of gallic acid. Standard conditions of reaction temperature and reaction time turn out to be 126 °C and 18 h, respectively. In addition, results show that reaction temperature has a stronger influence on different properties of the BiOI, affecting the photocatalytic efficiency. BiOI materials were synthesized by solvothermal process using different ranges of reaction temperature (120–200 °C) and reaction time (12–24 h). Eleven experiments were designed, applying response surface methodology. The morphological, optical, and chemical properties of the best and worst material were determined using several techniques.

Facet-dependent catalytic activity of nanosheet-assembled bismuth oxyiodide microspheres in degradation of bisphenol A.

Photocatalysts with different exposed facets often exhibit different photochemical performances, but the underlying mechanisms are not fully understood. In this study, we synthesized two nanosheet-assembled bismuth oxyiodide (BiOI) microspheres with exposed (110) and (001) facets, respectively, to further investigate facet-dependent photocatalytic activity. Our experimental results showed that the BiOI microspheres with exposed (110) facets exhibited much greater catalytic activity than the BiOI microspheres with exposed (001) facets in the degradation of bisphenol A under visible light irradiation. Density functional theory calculation revealed that the (110) facets can adsorb a greater amount of O2 and, thus, form more O2(•-) and (•)OH radicals than the (001) facets. The electron spin resonance spectroscopy and radical scavenging experiments verified that the BiOI microspheres with exposed (110) facets could produce a greater amount of O2(•-) radicals than the BiOI microspheres with exposed (001) facets, and more importantly, between the two BiOI products, only the BiOI microspheres with exposed (110) facets could generate (•)OH radicals directly. The facet-dependent radical formation mechanisms were previously unidentified. The findings of this study may have important implications for the understanding of the facet-dependent photochemical performance of photocatalysts and the design of novel catalytic materials with inorganic nanostructures.