Co-M(M=La,Ce,Fe,Mn,Cu,Cr)复合金属氧化物催化分解N_2O

通过共沉淀法制备了一系列Co-M(M=La,Ce,Fe,Mn,Cu,Cr)复合金属氧化物及纯Co_3O_4催化剂,考察了其催化分解N_2O的活性.结果表明在研究的系列催化剂中,Co-Ce复合氧化物催化剂具有最好的催化分解N_2O的活性;其活性与Ce/Co摩尔比有直接的关系,当Ce/Co摩尔比为0.05时(CoCe0.05催化剂)催化活性最佳;当有NO和O_2共存时,可能在催化剂活性中心上形成表面硝酸盐或亚硝酸盐吸附物种而使其活性受到较大影响.通过对Co-M催化剂的XRD、BET、O_2-TPD及H_2-TPR等表征结果的分析,发现作为主要活性位的Co^(2+)的氧化还原能力是影响催化剂活性的主要原因.这是因为根据反应机理,N_2O的表面分解步骤与Co^(2+)氧化成Co^(3+)的能力相关,而吸附氧的脱附与Co^(3+)还原成Co^(2+)的能力相关.在所研究的催化剂中,添加除CeO_2之外的其它过渡金属氧化物时,催化剂中Co^(3+)/Co^(2+)的氧化还原能力降低,因此其催化性能降低.另外,添加不同过渡金属氧化物也改变了N_2O催化分解反应的速控步骤.

光刻技术在整体式层板催化剂床研究中的应用

采用自主设计研制的高精度双面自对准光刻模具和标准MEMS光刻工艺技术研制出整体式层板催化剂床板片,简要介绍了光刻工艺原理、工艺流程和工艺过程。光刻加工出的板片满足设计要求,板片经过电镀和真空扩散焊接工艺形成了整体式催化剂床,该床成功地通过了热点火试车。催化剂床床载为16.5g/(cm2·s),分解效率为97%,室压粗糙度小于2%。

含氨典型废气净化及工程示范装置运行总结

采用吸收/吸附-催化有氧分解耦合工艺净化合成氨及尿素生产过程中产生的含氨废气。介绍了净化合成氨弛放气的工程示范装置的工艺操作条件、工艺流程及运行效果。氨含量约3%的弛放气经过离子液吸收塔处理后,气体中的氨平均浓度降到45×10-6以下,再经4级蒸馏后,回收氨的浓度可达95%;氢氨回收膜分离装置含少量氨的工艺尾气经催化反应器处理后,排放氨浓度小于1.4×10-6;弛放气中氨的净化率达到99.99%。

一级反应数据非线性拟合的Excel方法

分析了通常处理一级反应实验数据的方法存在的缺陷,给出了使用Excel做非线性拟合的方法和实例.

大象牙膏实验喷射成形影响因素研究

作为最具观赏性的化学实验之一,"大象牙膏"目前多数不能成形且喷射无力.系统的反应条件优化表明,过氧化氢质量分数、催化剂类别和用量、发泡剂类别和用量,以及反应容器等因素共同决定"大象牙膏"实验能否喷射成形.研究结果显示,使用质量分数为50%的H2O2(50 m L),KI(7.47 g,溶于15 m L水),洗洁精(12 m L),食用色素(5滴)的组合能够得到炫彩夺目、喷射力强且成形的"大象牙膏".

Superior performance of iridium supported on rutile titania for the catalytic decomposition of N_2O propellants

N2O is a promising green propellant and exhibits great potential for satellite propulsion systems. It is difficult for catalytic decomposition, which is an important way to initiate the propulsion process, to occur at temperatures below 600 °C due to the high activation energy of N2O. In this work, we report an Ir supported on rutile TiO2（Ir/r-TiO2） catalyst which exhibits a fairly high activity for high-concentration N2O decomposition. HAADF-STEM, H2-TPR, and XPS results indicate that highly dispersed Ir particles and improved oxygen mobility on the Ir/r-TiO2 could facilitate the decompo-sition of N2O and desorption of the adsorbed oxygen. Bridge-bonded peroxide intermediates were observed with in-situ DRIFT and herein, a detailed decomposition route is proposed.

Simultaneous hydrogen and peroxide production by photocatalytic water splitting

Photocatalytic oxidation of water is a promising method to realize large-scale H2O2 production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO2(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H2 and H2O2 production. Both H2 and H2O2 are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g^-1 h^–1 (first 1 h) for H2 and H2O2, respectively, which is much higher than that of a commercial Pt/TiO2(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H2O2, compared with the four-electron oxidation of water to O2.

Efficient destruction of sodium cyanide by thermal decomposition with addition of ferric oxide

Efficient destruction of cyanide by thermal decomposition with ferric oxide addition was proposed. The mechanism of destruction of sodium cyanide with or without ferric oxide addition under various conditions was examined by XRD, DSC-TG, and chemical analysis technologies. In the absence of ferric oxide, sodium cyanide decomposes at 587.4 ℃ in air and 879.2 ℃ in argon atmosphere. In the presence of ferric oxide, about 60% of sodium cyanide decomposes at 350 ℃ for 30 min in argon, while almost all sodium cyanide decomposes within 30 min in air or O2 with mass ratio of ferric oxide to sodium cyanide of 1:1. The increase of ferric oxide addition, temperature, and heating time facilitates the destruction of sodium cyanide. It is believed that with ferric oxide addition, NaCN reacts with Fe2O3 to form Na4Fe(CN)6, Na2CO3, NaNO2 and Fe3O4 in argon. NaCN decomposes into NaCNO, Na4Fe(CN)6, minor NaNO2, and the formed NaCNO and Na4Fe(CN)6 further decompose into Na2CO3, CO2, N2, FeOx, and minor NOx in air or O2.

Recent advances and perspectives in cobalt‐based heterogeneous catalysts for photocatalytic water splitting,CO_(2) reduction,and N_(2) fixation

Solar‐driven conversion of carbon dioxide,water and nitrogen into high value‐added fuels(e.g.H_(2),CO,CH_(4),CH_(3)OH,NH_(3) and so on)is regarded as an environmental‐friendly and ideal route for relieving the greenhouse gas effect and countering energy crisis,which is an attractive and challenging topic.Hence,various types of photocatalysts have been developed successively to meet the requirements of these photocatalysis.Among them,cobalt‐based heterogeneous catalysts emerge as one of the most promising photocatalysts that open up alluring vistas in the field of solar‐to‐fuels conversion,which can effectively enhance photocatalytic efficiency by extending light absorption range,promoting charge separation,providing active sites,and lowering reaction barrier.In this review,we first present the working principles of cobalt‐based heterogeneous catalysts for photocatalytic water splitting,CO_(2) reduction,and N_(2) fixation.Second,five efficient strategies including surface modification,morphology modulation,crystallinity controlling,crystal engineering and doping,are discussed for improving the photocatalytic performance with different types cobalt‐based catalysts(cobalt nanoparticles and single atom,oxides,sulfides,phosphides,MOFs,COFs,LDHs,carbide,and nitrides).Third,we outline the applications for the state‐of‐the‐art photocatalytic CO_(2) reduction and water splitting,and nitrogen fixation over cobalt‐based heterogeneous catalysts.Finally,the central challenges and possible improvements of cobalt‐based photocatalysis in the future are presented.The purpose of this review is to summarize the past experience and lessons,and provide reference for the further development of cobalt‐based photocatalysis technology.

Rational design and precise manipulation of nano‐catalysts

Nano‐catalysis plays a vital role in the chemical transformations and significantly impacts the booming modern chemical industry.The rapid technological enhancements have resulted in serious energy and environmental issues,which are currently spurring the exploration of the novel nano‐catalysts in diverse fields.In order to develop the efficient nano‐catalysts,it is essential to understand their fundamental physicochemical properties,including the coordination structures of the active centers and substrate‐adsorbate interactions.Subsequently,the nano‐catalyst design with precise manipulation at the atomic level can be attained.In this account,we have summarized our extensive investigation of the factors impacting nano‐catalysis,along with the synthetic strategies developed to prepare the nano‐catalysts for applications in electrocatalysis,photocatalysis and thermocatalysis.Finally,a brief conclusion and future research directions on nano‐catalysis have also been presented.

Electrocatalytic water oxidation by a nickel oxide film derived from a molecular precursor

In this study,we fabricated a NiOx film by electrodeposition of an ethanediamine nickel complex precursor(pH=11)on a fluorine‐doped tin oxide substrate.The resulting film is robust and exhibits high catalytic activity for electrochemical water oxidation.Water oxidation is initiated with an overpotential of375mV(1mA/cm2)and a steady current density of8.5mA/cm2is maintained for at least10h at1.3V versus the normal hydrogen electrode.Kinetic analysis reveals that there is a2e?/3H+pre‐equilibrium process before the chemical rate‐determining step.The low‐cost preparation,robustness,and longevity make this catalyst competitive for applications in solar energy conversion and storage.

Hierarchical coral-like FeNi(OH)_x/Ni via mild corrosion of nickel as an integrated electrode for efficient overall water splitting

Efficient,stable,and noble‐metal‐free electrocatalysts for both the oxygen evolution reaction and the hydrogen evolution reaction are highly imperative for the realization of low‐cost commercial water‐splitting electrolyzers.Herein,a cost‐effective and ecofriendly strategy is reported to fabricate coral‐like FeNi(OH)x/Ni as a bifunctional electrocatalyst for overall water splitting in alkaline media.With the assistance of mild corrosion of Ni by Fe(NO3)3,in situ generated FeNi(OH)x nanosheets are intimately attached on metallic coral‐like Ni.Integration of these nanosheets with the electrodeposited coral‐like Ni skeleton and the supermacroporous Ni foam substrate forms a binder‐free hierarchical electrode,which is beneficial for exposing catalytic active sites,accelerating mass transport,and facilitating the release of gaseous species.In 1.0 mol L^-1 KOH solution,a symmetric electrolyzer constructed with FeNi(OH)x/Ni as both the anode and the cathode exhibits an excellent activity with an applied potential difference of 1.52 V at 10 mA cm^-2,which is superior to that of an asymmetric electrolyzer constructed with the state‐of‐the‐art RuO2‐PtC couple(applied potential difference of 1.55 V at 10 mA cm^-2).This work contributes a facile and reliable strategy for manufacturing affordable,practical,and promising water‐splitting devices.

Ultrasound assisted electrocatalytic oxidation of 3-chlorophenol in aqueous solution

Ultrasound assisted electrocatalytic process was used for enhancing decomposition efficiency of organic compounds. In this paper, the effect of ultrasonic frequency, ultrasonic intensity and pH value on 3-chlorophenol decomposition were studied. It was found that 3-chlorophenol in aqueous solution can be markedly decomposed by ultrasound assisted electrocatalytic process. The rate of decomposition increased with the increase of frequency, and low frequency is proper in the ultrasound assisted electrocatalytic system. The removal of 3-chlorophenol increased visibly with the increase of ultrasonic intensity until the intensity of 1.56 W/cm2. Alkaline condition is beneficial to 3-chlorophenol decomposition, the rate at pH 9.08 was higher than pH 2.48 and 6.85. The major intermediate formed during 3-chlorophenol decomposition was 2-chloro-pbenzoquinone, which was readily decomposed by ultrasound assisted electrocatalytic process.

Time-resolved infrared spectroscopic investigation of Ga_(2)O_(3) photocatalysts loaded with Cr_(2)O_(3)-Rh cocatalysts for photocatalytic water splitting

Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated electrons in Ga_(2)O_(3) loaded with Cr_(2)O_(3)-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy.The structure of these Cr_(2)O_(3)-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy,as Rh particles partly covered with Cr_(2)O_(3).The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction.The loaded Cr_(2)O_(3) promotes electron transfer from Ga_(2)O_(3) to Rh,which accelerates the electron-consuming reaction for H2 evolution.Based on these observations,a photocatalytic water-splitting mechanism for Cr_(2)O_(3)-Rh/Ga_(2)O_(3) photocatalysts has been proposed.The elucidation of the roles of the Cr_(2)O_(3)-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.

Efficient development of Type-Ⅱ TiO_2 heterojunction using electrochemical approach for an enhanced photoelectrochemical water splitting performance

Type‐II‐heterojunction TiO2nanorod arrays(NAs)are achieved by a combination of reduced and pristine TiO2NAs through a simple electrochemical reduction.The heterojunction‐structured TiO2NAs exhibit an enhanced photo‐efficiency,with respect to those of pristine TiO2NAs and completely reduced black TiO2.The improved efficiency can be attributed to a synergistic effect of two contributions of the partially reduced TiO2NAs.The light absorption is significantly increased,from theUV to the visible spectrum.Moreover,the type II structure leads to enhanced separation and transport of the electrons and charges.The proposed electrochemical approach could be applied to various semiconductors for a control of the band structure and improved photoelectrochemical performance.

Direct decomposition of nitric oxide in low temperature over iron-based perovskite-type catalyst modified by Ru

Iron-based perovskite-type compounds modified by Ru were prepared through sol-gel process to study its catalytic activity of NOx direct decomposition at low temperature and evaluate the conversion of NO under the experimental conditions. The catalytic activity of La 0.9Ce 0.1Fe 0.8-nCo 0.2RunO3 （n=0.01,0.03,0.05,0.07,0.09）series for the NO, NO-CO two components, CO-HC-NO three components were also analyzed. The catalytic investigation evidenced that the presence of Ru is necessary for making highly activity in decomposition of nitric oxide even at low temperature（400 ℃）and La 0.9Ce 0.9Fe 0.75Co 0.2Ru 0.05O3 （n=0.05） has better activity in all the samples, the conversion of it is 58.5%. With the reducing gas（CO,C3H6）added into the gas, the catalyst displayed very high activity in decomposition of NO and the conversion of it is 80% and 92.5% separately.

Rh_2O_3/monoclinic CePO_4 composite catalysts for N_2O decomposition and CO oxidation

CePO4 （in particular, monoclinic CePO4） has been rarely used to make supported catalysts. Herein, monoclinic CeP04 nanoparticles were prepared by calcining hexagonal CePO4 nanomds （prepared by precipitation） in air at 900 ℃. Monoclinic CePO4 nanowires were prepared by calcining hexagonal CePO4 nanowires （prepared by hydrothermal synthesis at 150 ℃） in air at 900 ℃. Both monoclinic CePO4 materials were used to support Rh2O3 by impregnation using Rh（NO3）3 as a precursor （followed by calcination）. The catalytic performance of Rh2O3/monoclinic CePO4 composite materials in N2O decomposition and CO oxidation was investigated. It was found that Rh2O3 supported on monoclinic CePO4 nanowims was much more active than Rh2O3 supported on monoclinic CePO4 nanoparticles. The stability of catalysts as a function of reaction time on stream was studied in both reactions. The influence of co-fed CO2, O2, and H2O on the catalytic activity in N20 decomposition was also studied. These catalysts were characterized by employing N2 adsorption-desorption, ICP-OES, XRD, TEM, XPS, H2-TPR, O2-TPD, and CO2-TPD. The correlation between physicochemical properties and catalytic properties was discussed.

3D graphene foam-supported cobalt phosphate and borate electrocatalysts for high-efficiency water oxidation

The cobalt phosphate-/cobalt borate-based oxygen-evolving catalysts （OECs） are the important class of earth-abundant electrocatalysts that can operate with high activity for water splitting under benign conditions. This article reports the integration of cobalt phosphate （Co- Pi） and cobalt borate （Co-Bi） OECs with three-dimensional （3D） graphene foam （GF） for the electrocatalytic water oxidation reaction. The GF showed a unique advantage to serve as a highly conductive 3D support with large capacity for anchoring and loading Co-OECs, thereby facilitating mass and charge transfer due to the large amount of active sites provided by the 3D graphene scaffold. As a result, this integrated system of GF and Co-OECs exhibits synergistically enhanced catalytic activity. The overpotential （η） of Co-Pi and Co-Bi/graphene catalysts is about 0.390 and 0.315 V in neutral solutions, respectively. Besides, the integrated Co-OECs/graphene catalysts have also exhibited improved and stable oxygen evolution catalytic ability in alkaline solution.

Promoted porous Co_3O_4-Al_2O_3 catalysts for ammonia decomposition

Transition metal catalysts have been considerably used for NH3 decomposition because of the potential application in COx-free H2 generation for fuel cells. However, most transition metal catalysts prepared via traditional synthetic approaches performed the inferior stability due to the agglomeration of active components. Here, we adopted an efficient method, aerosol-assisted self- assembly approach （AASA）, to prepare the optimized cobalt-alumina （C0304-A1203） catalysts. The C0304-A1203 catalysts exhibited excellent catalytic performance in the NH3 decomposition reaction, which can reach 100% conversion at 600 ℃and maintain stable for 72 h at a gaseous hourly space velocity （GHSV） of 18000 cm3 gcat-1 h-1. The catalysts were characterized by various techniques including transmission electron microscope （TEM）, scanning electron microscope （SEM）, nitrogen sorption, temperature-programmed reduction by hydrogen （H2-TPR）, ex-situ/in-situ Raman and ex-situ/in-situ X-ray diffraction （XRD） to obtain the information about the structure and property of the catalysts. H2-TPR and in-situ XRD results show that there is strong interaction between the cobalt and alumina species, which influences the redox properties of the catalysts. It is found that even a low content of alumina （10 at%） is able to stabilize the catalysts due to the adequate dispersion and rational interaction between different components, which ensures the high activity and superior stability of the cobalt-alumina catalysts.

Double layered,one-pot hydrothermal synthesis of M-TiO_2(M=Fe^(3+),Ni^(2+),Cu^(2+)and Co^(2+)) and their application in photocatalysis

A double layered, one-pot hydrothermal method was adopted in this work to prepare transition metal ions （Fe3＋, Ni2＋, Cu2＋ and Co2＋） doped TiO〉 The morphology and chemical properties of TiO2 and the status of metal ions were characterized with XRD, TEM, BET, UV-Vis and XPS analysis. TEM images show that the obtained TiO2 was very uniform with an average particle size of 10.4 nm. XPS, TEM and XRD results show that transitional metals were doped onto TiO2 in the form of ions. Photocatalytic decomposition of oxalic acid under UV illumination and methylene blue degradation under visible light on these materials were conducted, respectively. The results reveal that Cu2＋-TiO2 and C02＋-TiO2 showed a highest activity under UV and visible light illumination, respectively, and they were both more active than commercial P25 TiO2. With this special design of double layers, the hydrolysis of titanium precursor in the system with water can be easily controlled and metal ions are simply doped. This strategy can be further applied to synthesize metal ion doped TiO2 using various metal precursors with controllable amounts, and thus lead to better optimization of highly active photocatalyst.