다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Bismuth-based semiconductors are a unique and promising group of recently developed advanced photocatalytic materials. They have been widely applied in several areas including the generation of H2 by splitting water, decomposition of organic and inorganic pollutants in both wastewater and polluted air, and organic synthesis through harvesting the energy of light. The electronic structure of bismuth-based semiconductors confers them with a suitable band gap for visible-light response and a well-dispersed valence band composed of hybrid orbitals of Bi6s and O2p, making them a promising candidate when compared to other metal oxide semiconductors. In addition, they are simple to operate and prepare with controlled morphologies, making them attractive as potential photocatalysts. The purposes of this review are (1) summarization of advanced bismuth-based compounds that have been applied to date, (2) statement of challenges facing this material and possible approaches to overcome them, and (3) suggestions for future work.

Bismuth-based photocatalytic semiconductors: Introduction, challenges and possible approaches

Nanoscale Bi-based photocatalysts are promising candidates for visible-light-driven photocatalytic environmental remediation and energy conversion. However, the performance of bulk bismuthal semiconductors is unsatisfactory. Increasing efforts have been focused on enhancing the performance of this photocatalyst family. Many studies have reported on component adjustment, morphology control, heterojunction construction, and surface modification. Herein, recent topics in these fields, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed. The progress in the enhancement mechanism involving light absorption, band structure tailoring, and separation and utilization of excited carriers, is also introduced. The challenges and tendencies in the studies of nanoscale Bi-based photocatalysts are discussed and summarized.

Review on nanoscale Bi-based photocatalysts

Bismuth oxyhalide layered materials for energy and environmental applications

In this work, Bi2O3/Bi2SiO5 p-n heterojunction photocatalyst was successfully fabricated via a facile one-step synthesis using Bi(NO3)3 and nano-SiO2 as precursors. With the increasing amount of SiO2, α-Bi2O3 gradually transferred into β-Bi2O3, and Bi2O3/Bi2SiO5 p-n heterojunction was obtained at the same time. The as-prepared samples were systematically characterized by XRD, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS). The Bi2O3/Bi2SiO5 heterojunction photocatalysts exhibited higher photocatalytic activity than α-Bi2O3 on the degradation of organic pollutants under simulated sunlight irradiation. The enhanced photocatalytic activity could be ascribed to the larger specific surface area, the larger contact angle, the formation of β-Bi2O3 and construction of p-n heterojunction. More importantly, the phase transition mechanism of Bi2O3 in Bi2O3/Bi2SiO5 heterojunction photocatalyst was proposed, which is significant for the theoretical study and application of photocatalytic materials.

/pdf/a-high-performance-bi2o3-bi2sio5-p-n-heterojunction-30faa6wavw.pdf

A high-performance Bi2O3/Bi2SiO5 p-n heterojunction photocatalyst induced by phase transition of Bi2O3

In order to develop low-cost photocatalyst, commercial Bi2O3 was utilized as raw material to prepare α-Bi2O3/BiOCl core-shell heterojunction via a facile in situ chemical transformation method. To clarify experimentally the band alignment relationships between the α-Bi2O3 and BiOCl (0 0 1), the α-Bi2O3/BiOCl (0 0 1) core–shell heterojunction band offsets were analyzed by X-ray photoelectron spectroscopy (XPS). Here based on energy gaps, valence band values of α-Bi2O3 and BiOCl (0 0 1), core levels difference of Bi 4f in α-Bi2O3/BiOCl (0 0 1) heterojunction, we demonstrate that band alignment of ∼0.28 eV exists between α-Bi2O3 and BiOCl with α-Bi2O3 possessing the higher valence band potential or electron affinity which is a driving force of valence band holes from α-Bi2O3 to BiOCl (0 0 1). While, the electrons in conduction band were driven to migrate through conduction band potential difference (0.49 eV) from BiOCl (0 0 1) to α-Bi2O3.

Band alignment and enhanced photocatalytic activation for α-Bi2O3/BiOCl (0 0 1) core–shell heterojunction

The assembling heterojunction, one of the key topics in photocatalysts and semiconductors (SCs), is generally accomplished in at least two steps, of which the first step is the synthesis of a matrix, and then the growth of the second phase on the matrix. Herein we present the preparation of α/β-Bi2O3 heterojunctions by an in situ phase transformation technique. Under normal pressure, a facile citrate method was used to synthesize β-Bi2O3 nanosheets and α/β-Bi2O3 heterojunctions. The novel features of the process are the mild operating conditions by an appropriate selection of heat treatment temperature and time. Using transmission electron microscopy (TEM), we found that a number of nano-sized α-Bi2O3 form on the β-Bi2O3 nanosheet via a controlled β→α phase transition, generating a large number of heterojunctions. The CM1 (calcining β-Bi2O3 precursor at 363 °C for 4 h) heterojunction achieves a strong visible light absorption and dye absorption capacity and produces a very high reaction rate for Rhodamine B (RhB) photodegradation. Electrochemical impedance spectroscopy (EIS) revealed excellent charge transfer characteristics of the heterojunction, which accounts for its high photoactivity. Using the X-ray electron valence band spectra, it is found that the valence band of α-Bi2O3 is more negative than that of β-Bi2O3. Thus, in heterojunctions, the photogenerated holes in β-Bi2O3 are transferred to α-Bi2O3 with good charge transport characteristics by the intrinsic driving force in the interface field. Furthermore, a separated hole can accomplish a transfer process from α-Bi2O3 to the aqueous solution within its lifetime due to the diameter of α-Bi2O3 being less than 17.6 nm.

Band alignment and enhanced photocatalytic activation of α/β-Bi2O3 heterojunctions via in situ phase transformation.

The proper band alignment of coupled semiconductor plays a key role on enhancing photocatalytic activity due to the valence and conduction difference in the interface to drive the photogenerated charge carrier separation. However, little is known about the exact band alignment of coupled semiconductors due to that most band alignments were schematic by valence of monocomponent, but not consider the interface effect of coupled semiconductors. Herein the novel synthesis strategy via in situ chemical transformation was successfully utilized to prepare BiVO4/BiOCl {001} heterojunctions. The results of transmission electron microscopy (TEM) show that BiVO4/BiOCl photocatalyst was made of BiOCl sheets and BiVO4 nanoparticles. The exact band alignment was experimentally demonstrated in BiVO4/BiOCl through X-ray photoelectron spectroscopy (XPS). The results show that the valence band difference is 0.58 eV which is a driving force valence of band holes from BiVO4 to BiOCl by the valence band offset. While the reductive electrons were driven by conduction band difference (1.27 eV) along the opposite direction compared to the oxidative holes. The large driving force for the charge transport across the interface explains the high photocatalytic activity achieved by the BiVO4/BiOCl.

Highly efficient photocatalytic activities, band alignment of BiVO4/BiOCl {001} prepared by in situ chemical transformation

We prepared an α-Bi2O3/BiOBr core–shell heterojunction via a facile in situ chemical transformation method. Ultrathin BiOBr nanosheets were observed and these were found to be evenly distributed on the surface of α-Bi2O3/BiOBr by SEM and TEM. The results revealed that the prepared α-Bi2O3/BiOBr photocatalysts were porous, and their specific surface areas were found to be raised on comparing with α-Bi2O3 and BiOBr. In our experiments, the photocatalytic activity of α-Bi2O3 was obviously enhanced when assembling with ultrathin BiOBr compared with α-Bi2O3/BiOBr and the individual phase. It is considered that the surface porous structure increases the specific surface areas, which improved the adsorption characteristics of α-Bi2O3/BiOBr. The suitable band alignment (between α-Bi2O3 and BiOBr) and oxygen vacancy effect can be attributed to the increased photocatalytic activity under visible irradiation.

Ze Wu

Papers

Band alignment and enhanced photocatalytic activation for α-Bi2O3/BiOCl (0 0 1) core–shell heterojunction

Band alignment and enhanced photocatalytic activation of α/β-Bi2O3 heterojunctions via in situ phase transformation.

Highly efficient photocatalytic activities, band alignment of BiVO4/BiOCl {001} prepared by in situ chemical transformation

An α-Bi2O3/BiOBr core-shell heterojunction with high photocatalytic activity.

Enhanced photocatalytic properties of molybdenum-doped BiVO4 prepared by sol–gel method