Photocatalytic activities of various pentavalent bismuthates under visible light irradiation

LiBiO₃, NaBiO₃, MgBi₂O₆, KBiO₃, ZnBi₂O₆, SrBi₂O₆, AgBiO₃, BaBi₂O₆ and PbBi₂O₆ were synthesized by various processes such as hydrothermal treatment, heating and so on. These materials were examined for their photocatalytic activities in the decolorization of methylene blue and decomposition of phenol under visible light irradiation. For methylene blue decolorization, the presence of KBiO₃ resulted in complete decoloration within 5 min. For phenol decomposition, NaBiO₃ showed the highest activity, while LiBiO₃, SrBi₂O₆ and BaBi₂O₆ possessed almost comparable decomposition rates. Their decomposition rates were apparently higher than that by anatase (P25) under UV irradiation.     

Large-Scale Synthesis of Porous Bi2O3 with Oxygen Vacancies for Efficient Photodegradation of Methylene Blue

Photocatalytic degradation of organic pollutants has become a hot research topic because of its low energy consumption and environmental-friendly characteristics. Bismuth oxide (Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document}) nanocrystals with a bandgap ranging from 2.0 eV to 2.8 eV have attracted increasing attention due to high activity of photodegradation of organic pollutants by utilizing visible light. Though several methods have been developed to prepare Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document}-based semiconductor materials over recent years, it is still difficult to prepare highly active Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} catalysts in large scale with a simple method. Therefore, developing simple and feasible methods for the preparation of Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} nanocrystals in large scale is important for the potential applications in industrial wastewater treatment. In this work, we successfully prepared porous Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} in large scale via etching commercial BiSn powders, followed by thermal treatment with air. The acquired porous Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} exhibited excellent activity and stability in photocatalytic degradation of methylene blue. Further investigation of the mechanism witnessed that the suitable band structure of porous Bi\begin{document}$ _2 $\end{document}O\begin{document}$ _3 $\end{document} allowed the generation of reactive oxygen species, such as O\begin{document}$ _2 $\end{document}\begin{document}$ ^{-\cdot} $\end{document} and \begin{document}$ \cdot $\end{document}OH, which effectively degraded MB.     

Self‐assembly of a cobalt(II)‐based metal–organic framework as an effective water‐splitting heterogeneous catalyst for light‐driven hydrogen production

The solar photocatalysis of water splitting represents a significant branch of enzymatic simulation by efficient chemical conversion and the generation of hydrogen as green energy provides a feasible way for the replacement of fossil fuels to solve energy and environmental issues. We report herein the self‐assembly of a Co^II‐based metal–organic framework (MOF) constructed from 4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetrabenzoic acid [or tetrakis(4‐carboxyphenyl)ethylene, H₄TCPE] and 4,4′‐bipyridyl (bpy) as four‐point‐ and two‐point‐connected nodes, respectively. This material, namely, poly[(μ‐4,4′‐bipyridyl)[μ₈‐4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetrabenzoato]cobalt(II)], [Co(C₃₀H₁₆O₈)(C₁₀H₈N₂)]_n, crystallized as dark‐red block‐shaped crystals with high crystallinity and was fully characterized by single‐crystal X‐ray diffraction, PXRD, IR, solid‐state UV–Vis and cyclic voltammetry (CV) measurements. The redox‐active Co^II atoms in the structure could be used as the catalytic sites for hydrogen production via water splitting. The application of this new MOF as a heterogeneous catalyst for light‐driven H₂ production has been explored in a three‐component system with fluorescein as photosensitizer and trimethylamine as the sacrificial electron donor, and the initial volume of H₂ production is about 360 µmol after 12 h irradiation.     

金属-有机框架材料在光催化二氧化碳还原中的应用

CO₂的过度排放导致全球环境问题日益严重,如何将CO₂有效地利用起来成为全世界的研究热点。相比于高耗能的CO₂捕获和储存(CCS)技术,通过催化反应将CO₂转化为有价值的能源燃料是同时解决能源危机和环境问题的有效途径。其中,使用太阳能作为能量来源的光催化CO₂还原技术更具应用前景。但是目前CO₂光还原催化剂仍然存在很多缺点,如可见光响应能力低、光生电子空穴对复合严重、CO₂吸附量小、产物的选择性低以及在含水环境中的产氢竞争反应等。金属-有机框架(MOFs)是由金属离子/簇和有机配体构成的一类独特的多孔晶态材料,具有可调的多孔结构、电子迁移速度快、CO₂吸附量大等优点,在光催化CO₂还原领域具有广阔的应用潜力。现有方法主要是通过对MOFs的功能化修饰、与其他功能型材料复合等获得高效的光还原CO₂的催化性能。本文主要对近年来MOFs基CO₂光还原催化剂(单一MOFs、MOFs基复合材料以及MOFs衍生材料)的研究现状进行了分析和讨论,并对MOFs材料在光催化CO₂还原中的发展趋势进行了展望。     

一种以还原氧化石墨烯为电子中继体的复合光催化剂的合成及光催化性能研究

本文构建了一种以还原氧化石墨烯( RGO) 为电子中继体的复合光催化体系 Pt-RGO / ZnIn2S4 - CoPi / BiVO4 ,并分别利用若丹明 B(RhB)的脱色和光催化分解水测试其催化性能。 在 RhB 的光催化脱色实验 中,反应 3h 后,溶液中 RhB 的脱色率高达 99. 89%。 在光催化分解水的过程中,反应 5h 之后,复合催化剂体 系产 H2 量达到 359. 6μmol,产氧量达到 196. 3μmol。 探讨了复合光催化剂体系的工作机理,发现其卓越的光 催化水处理效能主要缘于 RGO 作为电子中继体促进了光生电子在两个复合单体之间的传导,从而提高了系 统的光催化性能。     

P-doped g-C3N4 as an efficient photocatalyst for CO2 conversion into value-added materials: a joint experimental and theoretical study

The photocatalytic yield of g-C₃N₄ for CO₂ reduction was modified by phosphorus doping. Possible reaction pathways for CO₂ reduction on the P-doped g-C₃N₄ (PCN) surface were investigated by density function theory calculations for the first time. The experimental results showed that P doping increases the carriers' lifetime, which improves the production of CH₄ through the increase in the driving force of the electrons. The partial density of states of the PCN showed that the valence band maximum and conduction band minimum are composed of p_x, p_y, and, s orbitals of the N atoms and p_z states of carbon, nitrogen, and phosphorus, respectively. Mechanism studies confirm that formic acid, formaldehyde, methanol, and methane are the most probable products. Methane, having positive adsorption energy, can be easily desorbed from the PCN surface, and the Gibbs activation energy of the final step is 1.98 eV. The formation of H₂COOH is the rate-determining step.     

Perylene as a visible light photoredox catalyst for photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of MMA

Abstract

The organic photocatalyst, perylene, was used to mediate photoinduced electron transfer (PET) reversible addition-fragmentation chain transfer polymerization (RAFT) of methyl methhacrylate (MMA) under light irradiation in N,N-dimethylformamide (DMF) at 25°C with 4-cyanopentanoic acid dithiobenzoate (CPADB) as chain transfer agent (CTA). Kinetic studies confirmed that the polymerization obeyed the first order kinetic m'odel. The production of PMMAs with a good control of molecular weights (M_n,GPC) and narrow polymer molecular weight distribution (M_w/M_n) were obtained. It is found that well-controlled PET RAFT polymerization of MMA can be manipulated even with the amount of perylene decreasing to ppm level. No polymer was obtained in the absence of light irradiation, implying that the model of PET RAFT polymerization of MMA is an ideal light “on”-“off” switchable system. Furthermore, the speed of PET RAFT polymerization of MMA was also finely tunable by the external light irradiation intensity. The resultant PMMA macro-CTA was characterized by ¹H nuclear magnetic resonance spectrum (¹H NMR) and gel permeation chromatography (GPC). The accessibility of the high end group fidelity was further demonstrated by chain extension experiments.     

纳米薄膜光催化剂的制备与表面态研究

利用溶胶-凝胶提拉成膜法制备了TiO2,SnO2,Ag/SnO2,Ag/SnO2/TiO2纳米薄膜半导体催化剂.采用粉末电导法初步研究了纳米半导体薄膜催化剂的表面结构,测定了表面态能级相对于半导体导带边的位置.实验表明:四种催化剂在不同的表面能级位置都存在表面态:TiO2具有两类表面态,其能量分别为0.75eV和0.58eV.Ag/SnO2/TiO2由于Ag的担载,出现更负的表面态能级(0.33eV).这将会显著提高导带电子密度,加速光催化反应速率.     

Single-molecule Detection of Reactive Oxygen Species: Application to Photocatalytic Reactions

In this review, we have focused on the oxidation reactions of single dye molecules by reactive oxygen species (ROS). The methodologies for the single-molecule detection of ROS, such as hydroxyl radical (HO^•), singlet oxygen (O₂(a¹Δ_g)), and hydrogen peroxide (H₂O₂), have been introduced together with examples. In particular, a successful application using the single-molecule fluorescence technique for the investigation of the TiO₂ photocatalytic oxidation reactions is demonstrated in detail.