Synergy of photocatalytic reduction and adsorption for boosting uranium removal with PMo12/UiO-66 heterojunction

In this work, we proposed a new U(VI) removal strategy combining adsorption and photocatalytic reduction by the PMo₁₂/UiO-66 heterojunctions. The PMo₁₂ has been encapsulated in the cavities of UiO-66 by a one-step hydrothermal method, and the PMo₁₂/UiO-66 exhibited high adsorption capacity and photocatalytic activity. The maximal theoretical sorption capacity of U(VI) on 15% PMo₁₂/UiO-66 reached 225.36 mg/g and the photoreduction rate of 15% PMo₁₂/UiO-66 is about thirty times as much as UiO-66. Under the light irradiation, the photogenerated electrons rapidly transport from UiO-66 to PMo₁₂, and the photo-generated electrons could efficiently reduce the pre-enriched U(VI) to U(IV). This work provides new insights into remediation of the radioactive environment.     

Preparation and photocatalytic performance research of Bi2WO6/UiO-66-NH2 composite

Bi₂WO₆/UiO-66-NH₂ photocatalysts were fabricated through solvothermal method using acetic acid as template. The photocatalytic performance of as-fabricated composites was highly improved under simulated visible light due to the addition of UiO-66-NH₂. The structural and chemical properties of the composites were characterized through FTIR, XRD, XPS, SEM, BET, UV–vis DRS and PL. After 90 min of visible light irradiation, the RhB at an initial concentration of 10 mg·L^?1 in the solution was degraded by 99.4% due to the addition of 10 mg of the composite. There was no significant decrease in the photocatalytic activity even after four rounds of cycles. The free radical capture experiments indicate that the photogenerated holes (h⁺) were the main active sites. The possible photocatalytic degradation mechanism was proposed as the specific surface area of the composite was enlarged due to the uniform distribution of UiO-66-NH₂ on the surface of Bi₂WO₆. The electron–hole pairs recombination rate was decreased due to the photogenerated electrons (e^?) on the CB of Bi₂WO₆ which can be rapidly transferred to the CB of UiO-66-NH₂ and the photogenerated holes of UiO-66-NH₂ transferred to the VB of Bi₂WO₆. Meanwhile, the RhB was directly oxidized to H₂O and CO₂ by h⁺ to achieve the purification effect.

     

Sunlight photocatalytic degradation of ofloxacin using UiO-66/wood composite photocatalysts

This study synthesized UiO-66（Zr） in situ on wood via a one-step solvothermal method. UiO-66/wood was successfully prepared and its catalytic performance for the ofloxacin（OFX） photodegradation under simulate sunlight was also explored. Ui O-66/wood exhibited a better catalytic performance, and its degradation rate constant was about 1.2 and 1.5 times than that of UiO-66 and wood, respectively. The effects of solution initial concentration, pH of the system and dosage of the photocatalyst were e...     

S-型分级多孔CdS/UiO-66光催化剂的构建实现4-硝基苯胺的高效还原

金属有机框架(MOFs)材料因其高孔隙率特性在气体吸附分离、药物传递、催化等领域具有广泛应用.近年来,将功能化纳米颗粒(NPs)封装在MOFs中的研究在催化领域引起了科学家的兴趣.其中,较大比表面积的MOFs可以为NPs的分散和固定提供理想的平台,而NPs反过来可以为催化反应引入更多的活性位点,提高催化效率.然而,MOFs本身的孔隙常局限于微孔(<2 nm),这极大地限制了NPs在MOFs孔隙中的有效封装.因此,设计并制备含有介孔(2?50 nm)或大孔(>50 nm)的多级孔MOFs,揭示其孔径大小对复杂NPs/MOFs复合催化剂催化性能的影响具有重要意义.然而,具有不同孔径MOFs的可控制备具有巨大挑战性,MOFs孔径如何影响和调控NPs/MOFs复合材料催化活性是一个悬而未决的科学问题.本文结合金属离子刻蚀法和调控配体法设计了两种具有不同孔径(大孔和介孔)的UiO-66,并系统研究了孔径大小对CdS NPs的分布以及所形成的复合催化剂CdS/UiO-66的催化性能的影响及机制.我们首先阐明了UiO-66调控孔径后影响和修饰CdS NPs的空间分布:对于具有开放大孔结构的UiO-66纳米笼,CdS NPs倾向于自发沉积在UiO-66纳米笼内壁上.相比之下,CdS NPs则主要附着于介孔UiO-66的外表面.据此,具有大孔和介孔结构的CdS/UiO-66表现出不同的光催化性能.以光还原4-硝基苯胺反应为例,大孔CdS/UiO-66的反应速率常数是介孔和实心样品的3?13倍,且优于许多文献报道的CdS复合材料催化剂,表明大孔结构在制备高效复合催化材料上的潜在优势.通过光吸收能力、能级结构等计算表征,该催化剂的电子空穴对传输遵循S-型异质结光催化机制;大孔CdS/UiO-66具有较高光催化活性可归因于纳米笼对NPs的限域效应,即CdS被限制在UiO-66纳米笼内,缩短了催化剂与底物之间的电子传输距离;空心纳米笼结构则保护其内部的CdS NPs免受光腐蚀的影响,进而获得较高的催化效率和循环稳定性.可见,本文提出了一种结合离子刻蚀法和调控配体法获得具有不同孔径MOFs的有效策略,阐明了调控MOFs的孔径尺寸可以影响NPs的空间分布,是制约其性能的关键因素,有望为高效催化剂的设计及催化机制的研究提供新的依据.     

增强UiO-66-NH2光催化水分解制氢性能的研究进展

氢能是一种能量密度高、储量大、可再生、零污染的新能源。光催化水分解制氢是一种绿色、清洁的能源转换技术,被认为是一种有效的制氢方法。UiO-66-NH2是一种可见光响应、稳定性良好的金属有机骨架材料,但存在可见光响应范围有限、导电性差、载流子复合率高等问题。研究者们采用金属粒子掺杂、染料敏化、金属纳米粒子负载等多种方法对UiO-66-NH2进行改性,提升UiO-66-NH2在光催化水分解制氢反应中的性能,并报道了许多研究成果。因此,本文对近年来报道的有关增强UiO-66-NH2光催化水分解制氢性能的方法进行了综述,并对后续的发展提出了建议,以期为UiO-66-NH2在光催化水分解制氢中应用研究提供参考。     

CdSeTe NSs/TiO2 NTs的制备及其光电催化还原CO2的应用

利用水热法将CdSeTe纳米片组装到TiO2纳米管阵列上,制得CdSeTe NSs/TiO2 NTs催化剂.由扫描电子显微镜图(SEM)和高分辨透射电子显微镜图(HRTEM)可知,CdSeTe呈片状均匀平行生长于TiO2 NTs上.X射线衍射(XRD)数据表明片状CdSeTe主要沿着(100)、(002)晶面生长.由紫外可见漫反射光谱(UV-vis DRS)得到材料的能隙为1.48 eV,X射线光电子能谱(XPS)数据得到价带位置为1.02 eV.对材料的光电催化还原性能测试发现,CdSeTe NSs/TiO2 NTs与基底TiO2 NTs相比,光照时对CO2的电流密度明显提高.利用气相色谱检测发现光电催化还原CO2的主产物为甲醇,并对其还原机理从能带匹配理论、电子传输高效性和材料的稳定性三方面进行了解释.     

Construction of high-efficiency CoS@Nb2O5 heterojunctions accelerating charge transfer for boosting photocatalytic hydrogen evolution

The random movement and easy recombination of photoinduced charges lead to a low conversion efficiency for photocatalytic hydrogen evolution. The cocatalyst design is a promising route to address such problem through introducing an appropriate cocatalyst on the semiconductor photocatalysts to construct the high-efficiency heterojunctions. Herein, novel CoS/Nb₂O₅ heterojunctions were constructed via in-situ loading CoS cocatalyst on the surface of Nb₂O₅ nanosheets. Through the femtosecond-resolved transient absorption spectroscopy, the average lifetime of charge carriers for 10 wt% CoS/Nb₂O₅ (159.6 ps) is drastically shortened by contrast with that of Nb₂O₅ (5531.9 ps), strongly suggesting the rapid charge transfer from Nb₂O₅ to CoS. The significantly improved charge-transfer capacity contributes to a high photocatalytic hydrogen evolution rate of 355 µmol/h, up to 17.5 times compared with pristine Nb₂O₅. This work would provide a new design platform in the construction of photocatalytic heterojunctions with high charge-transfer efficiency.     

Synchronous activation of Ag nanoparticles and BiOBr for boosting solar-driven CO2 reduction

Artificial photosynthesis of valuable chemicals from CO₂ is a potential way to achieve sustainable carbon cycle. The CO₂ conversion activity is still inhibited by the sluggish charge kinetics and poor CO₂ activation. Herein, Ag nanoparticles coupled BiOBr have been constructed by in-situ photoreduction strategy. The crafting of interface between Ag nanoparticles and BiOBr nanosheets, achieving an ultra-fast charge transfer. The BiOBr semiconductor excited electrons and plasmonic Ag nanoparticles generated high-energy hot electrons synchronous accelerates the C=O double bond activation. Thus, the optimized Ag/BiOBr-2 heterostructure shows excellent CO₂ photoreduction activity with CO production of 133.75 and 6.83 µmol/g under 5 h of 300 W Xe lamp and visible light (λ > 400 nm) irradiation, which is 1.51 and 2.81 folds versus the pristine BiOBr, respectively. The mechanism of CO₂ photoreduction was in-depth understood through in-situ FT-IR spectrum and density functional theory calculations. This study provides some new perspectives into efficient photocatalytic CO₂ reduction.     

Facilely anchoring Cu2O nanoparticles on mesoporous TiO2 nanorods for enhanced photocatalytic CO2 reduction through efficient charge transfer

Semiconductor-employed photocatalytic CO₂ reduction has been regarded as a promising approach for environmental-friendly conversion of CO₂ into solar fuels. Herein, TiO₂/Cu₂O composite nanorods have been successfully fabricated by a facile chemical reduction method and applied for photocatalytic CO₂ reduction. The composition and structure characterization indicates that the Cu₂O nanoparticles are coupled with TiO₂ nanorods with an intimate contact. Under light illumination, all the TiO₂/Cu₂O composite nanorods enhance the photocatalytic CO₂ reduction. In particular, the TiO₂/Cu₂O-15% sample exhibits the highest CH₄ yield (1.35 µmol g^-1 h^-1) within 4 h irradiation, and it is 3.07 and 15 times higher than that of pristine TiO₂ nanorods and Cu₂O nanoparticles, respectively. The enhanced photoreduction capability of the TiO₂/Cu₂O-15% is attributed to the intimate construction of Cu₂O nanoparticles on TiO₂ nanorods with formed p-n junction to accelerate the separation of photogenerated electron-hole pairs. This work provides a reference for rational design of a p-n heterojunction photocatalyst for CO₂ photoreduction.     

Magnetron sputtering growth of AlN film for photocatalytic CO2 reduction

Research on Chemical Intermediates - Nitride has excellent optical properties and is a promising photocatalytic material. However, there are few studies on the effect of AlN on photocatalytic CO2...     

Fabrication of self-organized TiO2 nanotube arrays for photocatalytic reduction of CO2

The photocatalytic conversion of CO₂ and H₂O to alcohols was achieved using self-organized TiO₂ nanotube arrays (TNAs), which were prepared by electrochemical anodization of Ti foils in 1 M (NH₄)₂SO₄ electrolyte containing 0.5 wt% NH₄F. Experimental results revealed that the morphology and structure of self-organized TNAs could be strongly influenced by the applied voltage and anodization temperature, and the optimized TNAs were prepared by electrochemical anodization of Ti foils under optimal conditions (i.e., at 20 V for 2 h at 30 °C). The as-prepared TNAs were amorphous and could be transformed to anatase phase during the thermal treatment at 450 °C in air for 3 h. By using the annealed TNAs as a photocatalyst, the photocatalytic reduction of CO₂ to alcohol, predominately methanol and ethanol, was demonstrated under Xenon lamp illumination. Based on the photocatalytic measurements, the production rates of methanol and ethanol were calculated to be ～10 and ～9 nmol cm^?2 h^?1, respectively. In addition, the formation mechanism of methanol and ethanol was also tentatively proposed.     

2D/2D atomic double-layer WS2/Nb2O5 shell/core nanosheets with ultrafast interfacial charge transfer for boosting photocatalytic H2 evolution

Low-efficiency charge transfer is a critical factor to limit the photocatalytic H₂ evolution activity of semiconductor photocatalysts. The interface design is a promising approach to achieve high charge-transfer efficiency for photocatalysts. Herein, a new 2D/2D atomic double-layer WS₂/Nb₂O₅ shell/core photocatalyst (DLWS/Nb₂O₅) is designed. The atom-resolved HAADF-STEM results unravel the presence of an unusual 2D/2D shell/core interface in DLWS/Nb₂O₅. Taking advantage of the advanced femtosecond-resolved ultrafast TAS spectra, the average lifetime of charge carriers for DLWS/Nb₂O₅ (180.97 ps) is considerably shortened as compared to that of Nb₂O₅ (230.50 ps), strongly indicating that the 2D/2D shell/core interface enables DLWS/Nb₂O₅ to achieve ultrafast charge transfer from Nb₂O₅ to atomic double-layer WS₂, thus yielding a high photocatalytic H₂ evolution rate of 237.6 μmol/h, up to 10.8 times higher than that of pure Nb₂O₅ nanosheet. This study will open a new window for the development of high-efficient photocatalytic systems through the interface design.     

"反应环境磷酸化"加速g-C3N4/碳纸气-液-固三相界面光催化CO2还原

采用悬浮体系进行光催化CO2还原反应是将半导体光催化剂均匀分散到液相中,但液相中有限的CO2溶解度和扩散速率,极大限制了光催化还原CO2反应的活性和选择性.为了提高悬浮体系的CO2还原活性,研究人员进行了一系列研究,包括开发新材料、形貌调控、复合光催化剂和用CO2饱和溶液代替纯水等.但这些改进策略对CO2还原活性的提升是有限的,仍然难以达到实际应用的要求.近年来,关于催化剂的设计和制备方面取得较大进步,但仅有极少数的研究致力于构建有效的光催化体系.实际上,光催化体系的构建与催化剂的设计和制备同样重要,因为理想的光催化CO2还原体系会使CO2反应气体与光催化剂的相互作用最大化,从而提高CO2还原反应的效率.近年来,可以建立气-液-固三相接触界面的疏水基底材料被广泛研究并应用于许多领域,包括燃料电池、光催化、电催化和有机合成等.这种独特的界面体系可以使反应气体到达反应界面并吸附在催化剂表面,从而提高了许多涉及气体的多相反应的反应速率.在传统的固-液两相体系中,气体传输通常是限制反应速率的因素,疏水基底的引入则可以很好地解决这一问题.氮化碳(g-C3N4)作为一种聚合物半导体,具有可见光响应能力,并且光生电子具有足够的还原能力满足还原CO2的需求,这使得它逐渐成为光催化CO2还原领域的明星材料.本文把g-C3N4作为光催化剂负载到疏水基底表面,构建气-液-固三相光催化体系并用于研究光催化CO2还原反应活性.以三聚氰胺为前驱体,采用化学气相沉积法在亲、疏水碳纤维纸表面生长g-C3N4光催化剂来构建新型气-液-固三相光催化体系,该体系可以增强CO2的传输和吸附能力,并形成气-液-固(CO2-H2O-光催化剂)三相反应界面,使得光催化CO2还原反应的活性和选择性显著提高.借助于疏水表面,气态物质可以连续不断地输送到光催化剂表面,而不仅依赖于溶解在液相中的微量CO2气体.因此,催化剂表面可以保持有较高的CO2和较低的H+浓度,在抑制析氢反应的同时增强CO2还原反应.研究结果表明,与亲水样品相比,疏水样品的CO2还原效率显著提高并明显抑制了析氢反应,其光催化CO2还原反应的选择性达到78.6％.另外,氧化半反应通常是光催化CO2还原反应的限制因素,会导致光生空穴的大量聚集,阻碍光生载流子的分离与传递,进而影响整体的光催化转化率.研究结果表明,使用磷酸盐溶液代替纯水进行光催化CO2还原反应性能,可以大幅提高气-液-固三相体系的光催化活性,其总体光催化CO2还原速率达到了1175.5 μmol h-1 m-2,是纯水环境下的8.8倍,CO2还原选择性为93.8％.光催化剂表面的光生空穴可以直接与溶液中的磷酸根离子发生反应,使磷酸盐反应生成过磷酸盐,以代替较难发生的产氧半反应.     

Enhanced stability and CO2 affinity of a UiO-66 type metal-organic framework decorated with dimethyl groups

A new dimethyl-functionalized UiO-66 framework exhibits higher physicochemical stability, larger CO(2) uptake, and an enhanced heat of adsorption in comparison with what was previously observed for analogous UiO-66 type MOFs.     

在光催化还原CO2中具有高催化效率的八面体Cu2O修饰的TiO2纳米管

光催化还原CO2生成烃类燃料是一种可同时解决全球变暖和能源危机问题的最有效途径之一。尽管这方面的研究已经取得了一定的进展,但是整体的光催化转换效率还非常低。因此,需要发展更加高效的催化剂。由于半导体材料禁带宽度与太阳光谱相匹配,人们已经对其进行了广泛研究。其中TiO2因具有无毒、强氧化性以及良好的光学和电学性质等而成为最主要的研究对象。但是对于光催化还原CO2反应来说, TiO2仍存在很多不足,如只能吸收太阳光谱中的紫外光,光生载流子会快速结合,以及光生空穴的强氧化能力等,这些都限制了其光催化还原CO2的效率。采用窄禁带宽度半导体修饰TiO2是解决上述不足的有效途径之一。本文采用简单的电化学方法成功制备了一种由窄禁带半导体Cu2O修饰的TiO2纳米管(TNTs)的复合物,并运用扫描电子显微镜(SEM)、X射线衍射(XRD)以及X射线光电子能谱(XPS)表征了所制备复合物的形貌、化学组成和结晶度。表征结果显示,所制备的TiO2为整齐排列的纳米管阵列结构;复合物中的纳米颗粒为Cu2O;当电化学沉积Cu2O的时间为5 min时,得到的Cu2O纳米颗粒初步呈类八面体结构。随着沉积时间的增加, Cu2O颗粒尺寸增加,具有八面体结构。 XRD和XPS结果表明, TiO2纳米管为锐钛矿,八面体Cu2O纳米颗粒的主要暴露晶面为(111)面。我们还进一步研究了不同量Cu2O纳米颗粒修饰的TiO2纳米管复合物在可见光以及模拟太阳光下光催化还原CO2的能力。在可见光下,由于自身的禁带宽度,纯净的TiO2纳米管没有任何光催化还原CO2的能力;经过Cu2O纳米颗粒的修饰,复合物显现出明显的光催化还原CO2的能力,其中经过30 min Cu2O沉积的TNTs具有最高的光催化效率。在模拟太阳光下,经过15 min Cu2O沉积的TNTs具有最高的光催化效率。在所有光催化还原CO2过程中,主要碳氢产物为甲烷。为了深入地理解该复合体系在还原CO2中的高催化效率,我们对催化剂进行了进一步的表征。紫外-可见漫反射光谱表明, Cu2O八面体纳米颗粒的沉积将TNTs的吸收光谱拓展到了可见光区域,提高了复合物对太阳光的吸收能力。此外,我们还通过测试所制样品的光电流反应、荧光发射光谱以及电化学阻抗谱,研究了催化剂中光生电子和空穴的分离和迁移能力。结果表明,适量的Cu2O沉积提高了复合物对光的吸收能力,增加了光生载流子的数量,从而使更多的光生载流子参与光催化反应。综上,本文首次报道了八面体Cu2O纳米颗粒修饰TNTs复合物的光催化还原CO2的能力。在一定量的Cu2O纳米颗粒修饰下,该复合物在光催化还原CO2生成烃类反应中表现出高效性。经过一系列详细的表征和讨论,我们认为其高效性主要源于三个方面：(1) TNTs的管状结构为反应物的吸附提供了大量的活性位点,同时一维的管状结构更有利于光生载流子的运载,从而提高了电子和空穴的分离;(2) Cu2O纳米颗粒的修饰提高了催化剂对光的吸收,促进催化剂最大程度地利用太阳光;(3) TiO2和Cu2O之间导带以及价带位置的匹配,在减少光生载流子复合的同时也降低了TiO2价带上空穴的氧化能力,从而抑制了CO2还原产物的再氧化过程。     

Mixed Dimensional Nanostructure (UiO-66-Decorated MWCNT) as a Nanofiller in Mixed-Matrix Membranes for Enhanced CO2/CH4 Separation

Mixed-matrix membranes (MMMs) with combination of two distinct dimensional nanofillers (such as 1D-3D, 2D-3D, or 3D-3D, etc.) have drawn special attention for gas separation applications due to their concerted effects on gas permeation and mechanical properties. An amine-functionalized 1D multiwalled carbon nanotube (NH₂-MWCNT) with exceptional mechanical strength and rapid gas transport was crosslinked with an amine-functionalized 3D metal-organic framework (UiO-66-NH₂) with high CO₂ affinity in a Schiff base reaction. The resultant crosslinked mixed-dimensional nanostructure was used as a nanofiller in a polysulfone (PSf) polymer matrix to explore the underlying synergy between 1D and 3D nanostructures on the gas separation performance of MMMs. Cross-sectional scanning electron microscopy and mapping revealed the homogenous dispersion of UiO-66@MWCNT in the polymer matrix. The MMM containing 5.0 wt. % UiO-66@MWCNT demonstrated a superior permeability 8.3 Barrer as compared to the 4.2 Barrer of pure PSf membrane for CO₂. Moreover, the selectivity (CO₂/CH₄) of this MMM was enhanced to 39.5 from the 28.0 observed for pure PSf under similar conditions of pressure and temperature.     

Imidazolium-modification enhances photocatalytic CO2 reduction on ZnSe quantum dots

Colloidal photocatalysts can utilize solar light for the conversion of CO₂ to carbon-based fuels, but controlling the product selectivity for CO₂ reduction remains challenging, in particular in aqueous solution. Here, we present an organic surface modification strategy to tune the product selectivity of colloidal ZnSe quantum dots (QDs) towards photocatalytic CO₂ reduction even in the absence of transition metal co-catalysts. Besides H₂, imidazolium-modified ZnSe QDs evolve up to 2.4 mmol_CO g_ZnSe⁻¹ (TON_QD > 370) after 10 h of visible light irradiation (AM 1.5G, λ > 400 nm) in aqueous ascorbate solution with a CO-selectivity of up to 20%. This represents a four-fold increase in CO-formation yield and 13-fold increase in CO-selectivity compared to non-functionalized ZnSe QDs. The binding of the thiolated imidazolium ligand to the QD surface is characterized quantitatively using ¹H-NMR spectroscopy and isothermal titration calorimetry, revealing that a subset of 12 to 17 ligands interacts strongly with the QDs. Transient absorption spectroscopy reveals an influence of the ligand on the intrinsic charge carrier dynamics through passivating Zn surface sites. Density functional theory calculations indicate that the imidazolium capping ligand plays a key role in stabilizing the surface-bound *CO₂⁻ intermediate, increasing the yield and selectivity toward CO production. Overall, this work unveils a powerful tool of using organic capping ligands to modify the chemical environment on colloids, thus enabling control over the product selectivity within photocatalyzed CO₂ reduction.

A photocatalyst system consisting of ZnSe quantum dots modified with a thiolated imidazolium capping ligand for visible light-driven reduction of aqueous CO₂ to CO is reported without the need for a metal complex co-catalyst.     

氮自掺杂暴露（001）晶面TiO2微米片的可见光光催化CO2还原性能增强

化石能源的使用可产生大量CO2,带来严重的温室效应。光催化CO2还原生产太阳燃料技术既有望缓解温室效应,又可以将低能量密度的太阳能转化为高能量密度的化学能储存起来方便使用。高效光催化材料的开发是发展光催化技术的关键。迄今,在已开发的所有半导体光催化材料中, TiO2仍是广泛研究的明星材料。在实际使用中, TiO2的光催化效率仍受限于其极弱的可见光利用率和较高的电子-空穴复合几率。近年来,越来越多的研究表明TiO2的结构与形貌特征极大地影响其光催化效率。尤其, TiO2的外露晶面设计与晶面效应研究引起了广泛关注。由于具有较高表面能和较多表面不饱和键,起初大多数理论和实验研究认为锐钛矿TiO2(001)晶面是光催化活性晶面。后来,越来越多研究表明并非锐钛矿TiO2(001)晶面的暴露比例越高其光催化活性就越高。最近,我们发现锐钛矿TiO2(001)晶面与(101)晶面在调控光催化CO2还原性能上具有良好的协同效应。密度泛函理论计算表明,锐钛矿TiO2的(001)晶面与(101)晶面的能带结构有差异,(001)晶面的导带位置相对于(101)晶面而言较高,而(101)晶面的价带位置相对于(001)晶面而言较低。基于此我们提出,具有合适比例的锐钛矿TiO2的(001)晶面与(101)晶面的交界处可以形成最佳的表面异质结或晶面异质结。表面异质结的形成导致光生电子倾向于向(101)扩散,光生空穴倾向于向(001)扩散,从而促进光生电子-空穴分离,降低光生电子-空穴复合几率。在此工作基础上,我们直接以氮化钛为原料,氢氟酸为添加剂,通过简单的水热反应一步合成了氮自掺杂的TiO2微米片。利用X射线粉末衍射、扫描电镜、X射线光电子能谱、紫外-可见漫反射光谱、氮气吸附-脱附以及电化学阻抗谱等方法手段对所制备的光催化剂进行了基本结构与理化性质表征分析,并研究了其可见光光催化CO2还原性能。电镜照片结果表明,我们所制备的氮自掺杂锐钛矿TiO2微米片的(001)晶面与(101)晶面比例分别为65%和35%。基于我们前期研究结果, TiO2微米片的(001)晶面与(101)晶面可以形成表面异质结,具有良好的电荷分离效率,这也得到了电化学阻抗谱研究结果的证明。同时,由于N的原位掺杂,所制备的TiO2微米片具有优异的可见光捕获能力。由于可见光利用效率增强与光生电子-空穴分离效率提高这两方面的综合作用,所制备的氮自掺杂TiO2微米片具有非常好的可见光光催化CO2还原制甲醇性能,比商用P25及氮掺杂TiO2纳米粒子等参考样品的可见光光催化性能更优异。研究表明,通过原位自掺杂方法与晶面设计方法相结合,可以同时改善TiO2的可见光利用效率和光生电子-空穴分离效率,优化TiO2的可见光光催化性能,这也为后续开发新型高效光催化材料提供了新思路。     

Binuclear rhenium(I) complexes for the photocatalytic reduction of CO2

Binuclear rhenium(I) complexes with 1,2-bis(4,4'-methyl-[2,2']bipyridyl)-ethane and 1,2-bis(4,4'-methyl-[2,2']bipyridyl)-dodecane as bridging ligands and their mononuclear analogues have been synthesized and characterized by their spectroscopic and electrochemical properties. First reduction potentials and luminescence properties as well as the reductive quenching of the emissive state with TEOA were not affected by the alkyl linker. By means of a detailed comparison of the photocatalytic CO(2) reductions of the monometallic and the bimetallic complexes a great beneficial effect on the activity depending on the proximity of the centres was found. In high dilution the overall kinetics in the CO(2) photoreduction of mononuclear complexes are clearly monometallic. If the proximity of the centres is adjusted according to the lifetime of the OER (one electron reduced species) the photocatalytic activity is greatly improved showing a clear bimetallic mechanism. In the binuclear rhenium complexes, both the facile generation of a free coordination site and binuclear interactions for effective two electron transfer can be realized.     

Covalent attachment of a rhenium bipyridyl CO2 reduction catalyst to Rutile TiO2

We have characterized the covalent binding of the CO(2) reduction electrocatalyst ReC0A (Re(CO)(3)Cl(dcbpy) (dcbpy =4,4'-dicarboxy-2,2'-bipyridine)) to the TiO(2) rutile (001) surface. The analysis based on sum frequency generation (SFG) spectroscopy and density functional theory (DFT) calculations indicates that ReC0A binds to TiO(2) through the carboxylate groups in bidentate or tridentate linkage motifs. The adsorbed complex has the dcbpy moiety nearly perpendicular to the TiO(2) surface and the Re exposed to the solution in a configuration suitable for catalysis.