In situ Fourier Transform Infrared Spectroscopy Diagnostic for Characterization and Performance Test of Catalysts

The present work establishes a systematic approach based on the application of in-situ Fourier transform infrared spectroscopy （FTIR） for the investigation of the crystal structure, thermal stability, redox behavior （temperature-programmed reduction/temperatureprogrammed re-oxidation） as well as the catalytic properties of Co3O4 thin films. The syntheses of Co3O4 were achieved by chemical vapor deposition in the temperature range of 400-500℃. The structure analysis of the as-prepared material revealed the presence of two prominent IR bands peaking at 544 cm-1 （υ1） and 650 cm-1 （υ2） respectively, which originate from the stretching vibrations of the Co-O bond, characteristic of the Co3O4 spinel. The lattice stability limit of Co3O4 was estimated to be above 650℃. The redox properties of the spinel structure were determined by integrating the area under the emission bands υ1 and υ2 as a function of the temperature. Moreover, Co3O4 has been successfully tested as a catalyst towards complete oxidation of dimethyl ether below 340 ℃. The exhaust gas analysis during the catalytic process by in situ absorption FTIR revealed that only CO2 and H2O were detected as the final products in the catalytic reaction. The redox behavior suggests that the oxidation of dimethyl ether over Co3O4 follows a Mars-van Krevelen type mechanism. The comprehensive application of in situ FTIR provides a novel diagnostic tool in characterization and performance test of catalysts.

Identification of active sites for hydrogenation over Ru/SBA-15 using in situ Fourier-transform infrared spectroscopy

The active sites for hydrogenation over Ru/SBA‐15catalysts were identified using in situ Fourier‐transform infrared spectroscopy.The amount of active sites was proportional to the interfacial circumference of the Ru particles.In contrast,the rate of hydrogen spillover from Ru to the support was inversely proportional to the size of the Ru metal particles.Consequently,a catalyst with small Ru metal particles has a high rate of hydrogen spillover but a low density of active sites,whereas one with large Ru particles has a low rate of hydrogen spillover but a high density of active sites.The formation of these active sites is probably an intermediate step in hydrogen spillover.

In situ studies on ceria promoted cobalt oxide for CO oxidation

In situ studies of catalysts play valuable roles in observing phase transformation, understanding the corresponding surface chemistry and the mechanism of the reaction. In this paper, ceria promoted cobalt oxide was prepared by the calcination method and investigated for the CO oxidation. The microstructure and morphology of CeO2-Co3O4 were investigated by the Scanning Electron Microscope, High-resolution transmission electron microscopy, Raman and X-ray photoelectron spectroscopy characterization. The effect of CeO2 doping on Co3O4 for CO oxidation was characterized by in situ X-ray Diffraction (in situ XRD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). In situ XRD was carried out under H2 atmosphere to evaluate the redox property of catalysts. The results indicated that the ceria doping can enhance the reducibility of Co2+ and promote the Co3+-Co2+-Co3+ cycle, owing to the oxygen replenish property of CeO2. Furthermore, adsorbed carbonate species on the surface of CeO2-Co3O4 were investigated by in situ-DRIFTS experiment. It was turned out that carbonate species on ceria promoted cobalt oxide catalysts showed different IR peaks compared with pure cobalt oxide. The carbonate species on ceria promoted catalyst are more active, and similar to free state carbonate species with weak bonding to catalyst surface, which can effectively inhibit catalyst inactivation. This study revealed the mechanism of ceria promoting CO oxidation over cobalt oxide, which will provide theoretical support for the design of efficient CO oxidation catalysts.

Facile synthesis of Bi_(12)O_(17)Br_2 and Bi_4O_5Br_2 nanosheets:In situ DRIFTS investigation of photocatalytic NO oxidation conversion pathway

Bi12O17Br2and Bi4O5Br2visible‐light driven photocatalysts,were respectively fabricated by hydrothermal and room‐temperature deposition methods with the use of BiBr3and NaOH as precursors.Both Bi12O17Br2and Bi4O5Br2were composed of irregular nanosheets.The Bi4O5Br2nanosheets exhibited high and stable visible‐light photocatalytic efficiency for ppb‐level NO removal.The performance of Bi4O5Br2was markedly higher than that of the Bi12O17Br2nanosheets.The hydroxyl radical(?OH)was determined to be the main reactive oxygen species for the photo‐degradation processes of both Bi12O17Br2and Bi4O5Br2.However,in situ diffuse reflectance infrared Fourier transform spectroscopy analysis revealed that Bi12O17Br2and Bi4O5Br2featured different conversion pathways for visible light driven photocatalytic NO oxidation.The excellent photocatalytic activity of Bi4O5Br2resulted from a high surface area and large pore volumes,which facilitated the transport of reactants and intermediate products,and provided more active sites for photochemical reaction.Furthermore,the Bi4O5Br2nanosheets produced more?OH and presented stronger valence band holeoxidation.In addition,the oxygen atoms of NO could insert into oxygen‐vacancies of Bi4O5Br2,whichprovided more active sites for the reaction.This work gives insight into the photocatalytic pollutant‐degradation mechanism of bismuth oxyhalide.

聚光太阳能驱动二氧化碳甲烷化实验研究

针对聚光光热驱动CO_(2)甲烷化反应过程中聚光的作用机制尚不清晰的问题,以具有优异反应活性及光热转换特性的Ni/Al_(2)O_(3)催化剂为研究对象,开展了聚光光热驱动和热驱动下的CO_(2)甲烷化实验及机理研究。通过表观活化能测试、温度梯度实验及时间分辨的原位漫反射红外光谱实验,探究了聚光在反应过程中的作用机制,揭示了光热驱动CO_(2)甲烷化的反应机理。结果表明,与纯热驱动过程相比,光热驱动在相同温度下表现出更佳的催化性能。光热驱动下w(Ni)为15%的Ni/Al_(2)O_(3)催化剂在350℃下可达到86.8%的CO_(2)转化率,达到峰值转化率所需的温度比纯热驱动过程降低了25℃。此外,光热较热驱动过程的表观活化能降低了25%,且光致温度梯度进一步促进了CO_(2)的转化。时间分辨的原位漫反射红外光谱实验结果表明,聚光改善了CO_(2)在催化剂表面的吸附,促进了关键中间体的转变,增强了CO*生成CH4的反应路径,从微观动力学上促进了CO_(2)的转化。该研究为认识聚光太阳能驱动CO_(2)甲烷化过程中聚光的作用机制提供了新的思路。

Resistance to SO_2 poisoning of V_2O_5/TiO_2-PILC catalyst for the selective catalytic reduction of NO by NH_3

A titania pillared interlayered clay（Ti-PILC） supported vanadia catalyst（V2O5/TiO2-PILC） was prepared by wet impregnation for the selective catalytic reduction（SCR） of NO with ammonia. Compared to the traditional V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts, the V2O5/TiO2-PILC catalyst exhibited a higher activity and better SO2 and H2O resistance in the NH3-SCR reaction. Characterization using TPD, in situ DRIFT and XPS showed that surface sulfate and/or sulfite species and ionic SO4^（2-）species were formed on the catalyst in the presence of SO2. The ionic SO4^（2-） species on the catalyst surface was one reason for deactivation of the catalyst in SCR. The formation of the ionic SO4^（2-） species was correlated with the amount of surface adsorbed oxygen species. Less adsorbed oxygen species gave less ionic SO4^（2-） species on the catalyst.

Enhanced plasmonic photocatalysis by SiO_2@Bi microspheres with hot-electron transportation channels via Bi–O–Si linkages

The semimetal Bi has received increasing interest as an alternative to noble metals for use in plasmonic photocatalysis. To enhance the photocatalytic efficiency of metallic Bi, Bi microspheres modified by SiO2 nanoparticles were fabricated by a facile method. Bi-O-Si bonds were formed between Bi and SiO2, and acted as a transportation channel for hot electrons. The SiO2@Bi microspheres exhibited an enhanced plasmon-mediated photocatalytic activity for the removal of NO in air under 280 nm light irradiation, as a result of the enlarged specific surface areas and the promotion of electron transfer via the Bi-O-Si bonds. The reaction mechanism of photocatalytic oxidation of NO by SiO2@Bi was revealed with electron spin resonance and in situ diffuse reflectance infrared Fourier transform spectroscopy experiments, and involved the chain reaction NO -> NO2 -> NO3- with center dot OH and center dot O-2(-) radicals as the main reactive species. The present work could provide new insights into the in-depth mechanistic understanding of Bi plasmonic photocatalysis and the design of high-performance Bi-based photocatalysts. (C) 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Improving visible-light-driven photocatalytic NO oxidation over BiOBr nanoplates through tunable oxygen vacancies

In this work,a series of BiOBr nanoplates with oxygen vacancies(OVs)were synthesized by a solvothermal method using a water/ethylene glycol solution.The number of OVs and facets of BiOBr were tuned by changing the water/ethylene glycol ratio.Although the role of OVs in photocatalysis has been investigated,the underlying mechanisms of charge transfer and reactant activation remain unknown.To unravel the effect of OVs on the reactant activation and photocatalytic NO oxidation process,in situ diffuse reflectance infrared Fourier transform spectroscopy,so‐called DRIFTS,and theoretical calculations were performed and their results combined.The photocatalytic efficiency of the as‐prepared BiOBr was significantly increased by increasing the amount of OVs.The oxygen vacancies had several effects on the photocatalysts,including the introduction of intermediate energy levels that enhanced light absorption,promoted electron transfer,acted as active sites for catalytic reaction and the activation of oxygen molecules,and facilitated the conversion of the intermediate products to the final product,thus increasing the overall visible light photocatalysis efficiency.The present work provides new insights into the understanding of the role of OVs in photocatalysts and the mechanism of photocatalytic NO oxidation.

Surface Modification of (001) Facets Dominated TiO2 with Ozone for Adsorption and Photocatalytic Degradation of Gaseous Toluene

This study investigated the positive effect of surface modification with ozone on the photocatalytic performance of anatase TiO2 with dominated（001） facets for toluene degradation.The performance of photocatalyst was tested on a home-made volatile organic compounds degradation system. The ozone modification, toluene adsorption and degradation mechanism were established by a combination of various characterization methods, in situ diffuse reflectance infrared fourier transform spectroscopy, and density functional theory calculation.The surface modification with ozone can significantly enhance the photocatalytic degradation performance for toluene. The abundant unsaturated coordinated 5 c-Ti sites on（001）facets act as the adsorption sites for ozone. The formed Ti–O bonds reacted with H2O to generate a large amount of isolated Ti5 c-OH which act as the adsorption sites for toluene,and thus significantly increase the adsorption capacity for toluene. The outstanding photocatalytic performance of ozone-modified TiO2 is due to its high adsorption ability for toluene and the abundant surface hydroxyl groups, which produce very reactive OH·radicals under irradiation. Furthermore, the O2 generated via ozone dissociation could combine with the photogenerated electrons to form superoxide radicals which are also conductive to the toluene degradation.

In situ Raman,FTIR,and XRD spectroscopic studies in fuel cells and rechargeable batteries

As state-of-the-art electrochemical energy conversion and storage(EECS)techniques,fuel cells and rechargeable batteries have achieved great success in the past decades.However,modern societies’ever-growing demand in energy calls for EECS devices with high efficiency and enhanced performance,which mainly rely on the rational design of catalysts,electrode materials,and electrode/electrolyte interfaces in EESC,based on in-deep and comprehensive mechanistic understanding of the relevant electrochemical redox reactions.Such an understanding can be realized by monitoring the dynamic redox reaction processes under realistic operation conditions using in situ techniques,such as in situ Raman,Fourier transform infrared(FTIR),and X-ray diffraction(XRD)spectroscopy.These techniques can provide characteristic spectroscopic information of molecules and/or crystals,which are sensitive to structure/phase changes resulted from different electrochemical working conditions,hence allowing for intermediates identification and mechanisms understanding.This review described and summarized recent progress in the in situ studies of fuel cells and rechargeable batteries via Raman,FTIR,and XRD spectroscopy.The applications of these in situ techniques on typical electrocatalytic electrooxidation reaction and oxygen reduction reaction(ORR)in fuel cells,on representative high capacity and/or resource abundance cathodes and anodes,and on the solid electrolyte interface(SEI)in rechargeable batteries are discussed.We discuss how these techniques promote the development of novel EECS systems and highlight their critical importance in future EECS research.

原位DRIFTS在SCR过渡金属催化剂研究中的应用进展

概述了4类选择性催化还原(SCR)过渡金属催化剂的研发现状,归纳了原位漫反射红外傅里叶变换光谱(DRIFTS)在NH3和NO吸附转化过程研究中的应用进展,总结了SCR的反应机理及路径,并对原位DRIFTS在SCR研究中的应用前景进行了展望。指出,基于原位DRIFTS技术可遴选出影响催化剂SCR活性的要素,这些要素包括NH3和NO在催化剂上的吸附方式、物种间的活化转化、中间体及(副)产物的生消过程等,这对针对性合成具有特殊结构和形貌的高活性催化剂具有重要指导作用。

原位傅里叶变换红外光谱研究Y型分子筛表面酸性对吸附有机分子的影响

采用吡啶原位吸附傅里叶变换红外(Py-FTIR)光谱对液相离子交换(LPIE)和固相离子交换(SSIE)法制备的CeY分子筛以及HY和NaY的酸性进行了测定.在原位条件下采用单探针分子噻吩、环己烯和苯对其在分子筛上的吸附过程进行了研究;以噻吩和环己烯、噻吩和苯组成的双探针分子对吸附过程中存在的竞争吸附、催化反应以及吸附机理进行了系统研究.结果表明,HY和L-CeY分子筛表面强Brnsted(B)酸性位可导致吸附在其表面的噻吩发生低聚反应以及吸附的环己烯产生二聚环己烯碳正离子.低聚的噻吩和吸附的环己烯在分子筛上发生强的化学吸附,进一步抑制和阻碍噻吩硫化物与分子筛吸附活性中心发生作用,从而降低了吸附剂的选择性以及吸附硫化物的能力.吸附剂表面Lewis(L)酸中心是吸附的主要活性中心,大量弱的L酸,有利于噻吩吸附.并且,S-CeY分子筛表面弱的L酸对吸附噻吩具有一定的选择性,它受到环己烯的影响较小,NaY吸附剂对噻吩、环己烯和苯选择性较差,它只与吸附质作用的先后有关.

Ce改性对Y型分子筛酸性及其催化转化性能的调变机制

采用液相离子交换(LPIE)法制备了不同离子交换度的Ce Y分子筛.运用电感耦合等离子发射光谱(ICPAES)、X射线衍射(XRD)、N2吸附等温线和氨气程序升温脱附(NH_3-TPD)等方法对其进行表征,采用原位傅里叶变换红外(in situ FTIR)光谱技术分别以吡啶和噻吩作为探针分子研究了Ce改性对Y型分子筛酸性能和催化转化性能的影响规律.结果表明,Ce离子改性不改变Y型分子筛晶体的基本骨架,但改变其精细结构.分子筛改性过程中Ce物种优先定位于方钠石(SOD)笼,随着稀土离子含量增大,逐渐出现在超笼中.Ce离子交换过程中产生一定量的Brnsted(B)酸中心,且其量与强度随着Ce含量的增大均呈现先增加后平稳的趋势.同时,Ce离子交换产生与非骨架铝物种和铈物种有关的两种强度不同的Lewis(L)酸中心,且两者均随着Ce含量的增大而增大.噻吩吸附红外光谱表明,由于Ce离子改性产生的强B酸中心可导致噻吩在室温条件下即可发生质子化反应,质子化的噻吩分子可进一步发生低聚反应.而稀土物种与B酸中心的协同作用有利于低聚反应的发生.

紫铜表面3-巯丙基三乙氧基硅烷薄膜的制备与耐蚀性能

利用傅里叶变换红外(FTIR)光谱分析了3-巯丙基三乙氧基硅烷分别在酸性和碱性的醇-水溶液中水解后以及在紫铜表面成膜后的结构特征.利用极化曲线、电化学阻抗谱(EIS)和盐水浸泡实验测试了硅烷膜的耐腐蚀性能.结果表明:3-巯丙基三乙氧基硅烷在酸性溶液中能够发生一定程度的水解并生成Si―OH结构,且当该溶液在自然状态下晾干后,其水解程度进一步增大.在碱性溶液中该硅烷只发生少量的水解,溶液中含有较多SiOCH2CH3结构,且在溶液自然晾干后水解程度也没有明显增大.由酸性硅烷溶液制得的薄膜中硅烷分子以Si―O―Si键相互交联的程度比由碱性硅烷溶液制得的薄膜高.硅烷膜降低了紫铜电极的腐蚀电流密度,其保护效率分别为90.3%(酸性)和79.2%(碱性).在3.5%(w)NaCl溶液中浸泡24h后,由酸性溶液制得的薄膜表现出更高的阻抗值,而由碱性溶液制得的薄膜则基本失去了对基底的保护能力.

常温下MnO_2/Al_2O_3催化剂催化臭氧氧化甲苯反应

采用浸渍法制备了Al2O3负载的5种过渡金属氧化物催化剂,考察了它们在常温下催化臭氧氧化甲苯的性能,并运用程序升温还原、程序升温氧化、N2吸附-脱附和X射线光电子能谱对催化剂进行了表征.结果表明,NiO/Al2O3,CoO/Al2O3和MnO2/Al2O3催化剂上活性氧中心数量较少,臭氧与甲苯转化率较高;而Fe2O3/Al2O3和CuO/Al2O3催化剂上则相反.催化降解臭氧效率较高的催化剂上甲苯转化率也较高,在本文实验条件下,CO2产率低于30%.当甲苯浓度为666mg/m3,O3浓度从193mg/m3提高至965mg/m3时,甲苯转化率从15.2%提高至46.7%,并且使反应后催化剂表面产物和晶格氧含量增加.原位漫反射红外光谱研究发现,反应过程中生成了含COO-,C=O和C-O官能团的物质,O3浓度的提高加速了COO-向C=O与C-O的转化,前者在573KO2气氛下几乎不发生反应,而后者在373K开始分解.基于此,提出了常温下臭氧催化氧化甲苯的反应机理.

离子液体BMIMBF4中对甲氧基甲苯的电化学氧化

以离子液体1-丁基-3-甲基咪唑四氟硼酸盐(BMIMBF4)为电解质,采用循环伏安法(CV)、计时电流法(CP)、原位傅里叶变换红外光谱(in situ FTIRS)法等手段研究了对甲氧基甲苯(p-MT)在铂电极上的电氧化行为.实验结果表明:对甲氧基甲苯在离子液体中的电化学氧化反应是受扩散控制的四电子不可逆过程,估算了其扩散系数D=3.4×10-7cm2.s-1,主要电氧化产物为茴香醛,加入适量的水或适当提高温度有利于电氧化反应向生成相应醛的方向进行.

原位漫反射傅里叶变换红外光谱研究锰铁基催化剂上低温选择性催化还原反应机理(英文)

采用自蔓延燃烧法制备了Ti0.9Mn0.05Fe0.05O2-δ催化剂,运用原位漫反射傅里叶变换红外光谱对该催化剂的NO和NH3稳态吸附以及NO和NH3瞬态反应进行了详细地分析与讨论.结果表明,相比于Lewis酸性位,150 oC时Brnsted酸性位吸附的NH3更具有SCR活性;与双齿硝酸盐和桥式硝酸盐相比,NO吸附产生的单齿硝酸盐是主要的中间物种;该SCR反应遵循Eley-Rideal和Langmuir-Hinshelwood机理,但以后者为主.另外,O2的存在有利于NO的氧化和配位态NH3的活化.

钛硅分子筛TS-1上液相氨氧化制环己酮肟机理的原位红外研究

采用原位漫反射红外光谱法,对TS-1上环己酮和氨水、过氧化氢液相氧化反应体系进行了研究。结果表明,环己酮和氨水各自吸附,它们的混合物吸附均发生在表面—Si—OH,且二者相互作用生成亚胺中间物;过氧化氢与TS-1作用形成Ti的过氧化物—Ti—OOH,它与亚胺反应可形成肟。亚胺机理可以很好地解释一些高沸点有机物形成的原因。

连续在线原位ATR-FTIR技术测定介孔CuAl_2O_4对黄药的吸附

以丁胺和正十二醇为混合模板剂,采用共沉淀法制备了介孔纳米CuAl_2O_4.用X射线粉末衍射(XRD)、傅里叶变换红外(FTIR)光谱、N_2吸附-脱附对产物的结构进行了表征.采用连续在线原位衰减全反射傅里叶变换红外(ATR-FTIR)光谱技术研究了水溶液中丁基和辛基黄药在介孔CuA_l2O_4表面的吸附.随着吸附时间的延长,1200和1040 cm^(-1)两处黄药特征峰的高度逐渐增加,根据1200 cm^(-1)处C—O—C伸缩振动峰的变化来评价黄药在CuAl_2O_4表面的吸附动力学过程.结果表明,介孔纳米CuAl_2O_4对黄药有很强的吸附能力,在100 min的时间内,CuAl_2O_4样品对丁基和辛基黄药的吸附量分别达到了236和300 mg·g^(-1),且属于化学吸附.对实验数据进行理论模拟,发现吸附过程更接近于拟二级吸附动力学方程.

Rubberband方法中分段数量的选择对基线校正效果的影响分析

针对混合气体红外光谱在应用现场基线漂移和畸变、基线校正方法 Rubberband方法中分段数量的选择不确定等问题进行探讨,通过遍历的形式筛选出针对烃类气体在中红外波段、波数分辨率为4 cm^-1的情况下,优选出分段数量在50-120之间、基线点的曲线拟合方法选择分段三次Hermite插值方法时,其基线估计和校正的效果较为理想。同时针对Rubberband方法易将吸收点误判为基线点的问题,使用中位数和偏离度首先剔除分段内的明显吸收点,然后将剩余谱线点采用偏最小二乘方法设定一定的阈值范围进行基线点的筛选,筛选出的基线点在整个波段采用分段三次Hermite插值方法进行基线的估计。从实测的光谱基线校正效果来看,提出的算法使用简单,并适合于在线连续分析的应用场合。