Visualization of Heterogeneous Oxygen Storage Behavior in Platinum‐Supported Cerium‐Zirconium Oxide Three‐Way Catalyst Particles by Hard X‐ray Spectro‐Ptychography

The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce₂Zr₂O_x (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce₂Zr₂O_x particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts.     

Visualization of the Heterogeneity of Cerium Oxidation States in Single Pt/Ce2Zr2Ox Catalyst Particles by Nano‐XAFS

The cerium oxidation states in single catalyst particles of Pt/Ce₂Zr₂O_x (x=7 to 8) were investigated by spatially resolved nano X‐ray absorption fine structure (nano‐XAFS) using an X‐ray nanobeam. Differences in the distribution of the Ce oxidation states between Pt/Ce₂Zr₂O_x single particles of different oxygen compositions x were visualized in the obtained two‐dimensional X‐ray fluorescent (XRF) mapping images and the Ce L_III‐edge nano X‐ray absorption near‐edge structure (nano‐XANES) spectra.     

A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce20M1Ox (M=Zr,Cr, Mn,Fe, Co,Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide

This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce₂₀M₁O_x (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N₂ physisorption, X‐ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X‐ray photoelectron spectroscopy, temperature‐programmed reduction by hydrogen and by oxygen (H₂‐TPR and O₂‐TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M^x+ into the lattice of CeO₂ increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O₂^? (and/or O^?) species of these Ce₂₀M₁O_x composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce₂₀Cr₁O_x exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near‐surface Ce³⁺ and Cr³⁺. Finally, a possible reaction mechanism was tentatively proposed to understand the reactions.     

Bulk and surface analysis of Ti1–xFexO2/Fe2O3 composites prepared by solid state reaction for photocatalytic applications

Ti_1–xFe_xO₂ / Fe₂O₃ (x = 0.3, 0.6, and 0.7 wt%) composites were prepared by solid state reaction of the oxides TiO₂ (rutile phase) and Fe₂O₃ at 550 °C. The following techniques were applied for the characterization of the composites: X‐ray powder diffraction, Mössbauer spectroscopy, SEM, energy dispersive X‐ray spectroscopy and adsorption of nitrogen. The anatase/rutile/hematite ratio and the abundance of Fe³⁺ were quantified. The results indicate that Fe³⁺ substituted Ti⁴⁺ in the rutile structure and that the α‐Fe₂O₃ phase was predominantly on the surface of the crystalline Ti_1–xFe_xO₂ powders. A substantial increase of the materials density, with respect to rutile, favoured the application of the composites in photocatalytic experiments. The performance of the solids upon the photodegradation of aqueous solutions of carbofuran was evaluated. The Lewis sites created in the composites correlated directly with the photodegradation rate constant of carbofuran and the decrease of the total organic carbon content in the treated solutions. Copyright © 2011 John Wiley & Sons, Ltd.     

Highly Dispersed Ce x Zr1−x O2 Nano-Oxides Over Alumina, Silica and Titania Supports for Catalytic Applications

We have been exploring the utilization of supported ceria and ceria–zirconia nano-oxides for different catalytic applications. In this comprehensive investigation, a series of Ce _x Zr_1−x O₂/Al₂O₃, Ce _x Zr_1−x O₂/SiO₂ and Ce _x Zr_1−x O₂/TiO₂ composite oxide catalysts were synthesized and subjected to thermal treatments from 773 to 1073 K to examine the influence of support on thermal stability, textural properties and catalytic activity of the ceria–zirconia solid solutions. The physicochemical characterization studies were performed using X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HREM), thermogravimetry and BET surface area methods. To evaluate the catalytic properties, oxygen storage/release capacity (OSC) and CO oxidation activity measurements were carried out. The XRD analyses revealed the formation of Ce_0.75Zr_0.25O₂, Ce_0.6Zr_0.4O₂, Ce_0.16Zr_0.84O₂ and Ce_0.5Zr_0.5O₂ phases depending on the nature of support and calcination temperature employed. Raman spectroscopy measurements in corroboration with XRD results suggested enrichment of zirconium in the Ce _x Zr_1−x O₂ solid solutions with increasing calcination temperature thereby resulting in the formation of oxygen vacancies, lattice defects and oxygen ion displacement from the ideal cubic lattice positions. The HREM results indicated a well-dispersed cubic Ce _x Zr_1−x O₂ phase of the size around 5 nm over all supports at 773 K and there was no appreciable increase in the size after treatment at 1073 K. The XPS studies revealed the presence of cerium in both Ce⁴⁺ and Ce³⁺ oxidation states in different proportions depending on the nature of support and the treatment temperature applied. All characterization techniques indicated absence of pure ZrO₂ and crystalline inactive phases between Ce–Al, Ce–Si and Ce–Ti oxides. Among the three supports employed, silica was found to stabilize more effectively the nanosized Ce _x Zr_1−x O₂ oxides by retarding the sintering phenomenon during high temperature treatments, followed by alumina and titania. Interestingly, the alumina supported samples exhibited highest OSC and CO oxidation activity followed by titania and silica. Details of these findings are consolidated in this review.     

Preparation and Photocatalytic Properties of Ti1-xZrxO2 Solid Solution

A series of Ti1-xZrxO2 materials were synthesized through a multistep sol-gel process. The structural characteristics were investigated using X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and Raman measurements. The experimental results showed that a solid solution could be obtained at low Zr/（Ti＋Zr） molar ratios （x ≤0.319）. Raman measurements exhibited that the presence of zirconium in the solid solutions greatly retarded the amorphous-anatase and anatase-rutile transitions. The diffuse reflectance UV-Vis spectra revealed that the bandgap of the solid solution was enlarged gradually with the increment of incorporated zirconium content. The Ti1-xZrxO2 solid solutions exhibited higher photocatalytic activity than pure TiO2 for the degradation of 4-chlorophenol aqueous solution.     

Catalytic Hydrogenation of Acetic Acid to Acetaldehyde: Synergistic Effect of Bifunctional Co/Ce‐Fe Oxide Solid Solution Catalysts

The large‐scale industrial production of acetic acid (HAc) from carbonylation of methanol has enabled intense research interest from direct hydrogenation of HAc to acetaldehyde (AA). Herein, a series of cerium‐iron oxide solid solution supported metallic cobalt catalysts were prepared by modified sol‐gel method and were applied in gas‐phase hydrogenation of HAc to AA. A synergistic effect between the hydrogenation metal cobalt and Ce‐Fe oxide solid solution is revealed. Specifically, oxygen vacancies provide the active sites for adsorption of HAc, while highly uniformly dispersed metallic Co adsorbs H₂ and activates the reduction of HAc into AA. Moreover, the metallic Co can also assist the cyclical conversion between Fe³⁺/Fe²⁺ and Ce³⁺/Ce⁴⁺ on the surface of Ce_1‐xFe_xO_2‐δ supports. The unique effect substantially enhances the ability of the support material to rapidly capture oxygen atoms from HAc. It is found that the catalyst of 5% Co/Ce_0.8Fe_0.2O_2‐δ with the highest concentration of oxygen vacancy presents the best catalytic performance (i.e. acetaldehyde yield reaches 49.9%) under the optimal reaction conditions (i.e. 623 K and H₂ flow rate = 10 mL/min). This work indicates that the Co/Ce‐Fe oxide solid solution catalyst can be potentially used for the selective hydrogenation from HAc to AA. The synergy between the metallic Co and Ce_1‐xFe_xO_2‐δ revealed can be extended to the design of other composite catalysts.     

Synthesis and structure determination of Ce6Cd23Te: a new chalcogen‐containing member of the RE6Cd23T family (RE is a rare‐earth metal and T is a late group 14, 15 and 16 element)

The ternary phase hexacerium tricosacadmium telluride, Ce₆Cd₂₃Te, was synthesized by a high‐temperature reaction of the elements in sealed Nb ampoules and was structurally characterized by powder and single‐crystal X‐ray diffraction. The structure, established from single‐crystal X‐ray diffraction methods, is isopointal with the Zr₆Zn₂₃Si structure type (Pearson symbol cF 120, cubic space group Fm m ), a filled version of the Th₆Mn₂₃ structure with the same space group and Pearson symbol cF 116. Though no Cd‐containing rare‐earth metal binaries are known to form with this structure, it appears that the addition of small amounts of a p‐block element allows the formation of such interstitially stabilized ternary compounds. Temperature‐dependent direct current (dc) magnetization measurements suggest local‐moment magnetism arising from the Ce³⁺ ground state, with possible valence fluctuations at low temperature, inferred from the deviations from the Curie–Weiss law.     

Catalytic Properties of Nanoscale Iron‐Doped Zirconia Solid‐Solution Aerogels

Nanoscale iron‐doped zirconia solid‐solution aerogels are prepared via a simple ethanol thermal route using zirconyl nitrate and iron nitrate as starting materials, followed by a supercritical fluid drying process. Structural characteristics are investigated by means of powder X‐ray diffraction (XRD), thermal analyses (TG/DTA), N₂ adsorption measurements and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that the resulting iron‐doped solid solutions are metastable tetragonal zirconia which exhibit excellent dispersibility and high solubility of iron oxide. Further, when the Fe:(Fe+Zr) ratio x is lower than 0.10, all of the Fe³⁺ ions can be incorporated into ZrO₂ by substituting Zr⁴⁺ to form Zr_1?xFe_xO_y solid solutions. Moreover, for the first time, an additional hydroxyl group band that is not present in pure ZrO₂ is observed by DRIFTS for the Zr(Fe)O₂ solid solution. This is direct evidence of Fe³⁺ ions incorporated into ZrO₂. These Zr_1?xFe_xO_y solid solutions are excellent catalysts for the solvent‐free aerobic oxidation of n‐hexadecane using air as the oxidant under ambient conditions. The Zr_0.8Fe_0.2O_y solid‐solution catalyst demonstrates the best catalytic properties, with the conversion of n‐hexadecane reaching 36.2 % with 48 % selectivity for ketones and 24 % selectivity for alcohols and it can be recycled five times without significant loss of activity.     

Role of yttrium loading in the physico-chemical properties and soot combustion activity of ceria and ceria–zirconia catalysts

Ce_1−xY_xO₂ and Ce_0.85−xZr_0.15Y_xO₂ mixed oxides have been prepared by 1000 °C-nitrates calcination to ensure thermally stable catalysts. The physico-chemical properties of the mixed oxides have been studied by N₂ adsorption at −196 °C, XPS, XRD, Raman spectroscopy and H₂-TPR, and the catalytic activity for soot oxidation in air has been studied by TG in the loose and tight contact modes. Yttrium is accumulated at the surface of Ce_1−xY_xO₂ and Ce_0.85−xZr_0.15Y_xO₂, and this accumulation is more pronounced for the former formulation than for the latter, because the deformation of the lattice due to zirconium doping favours yttrium incorporation. Yttrium and zirconium exhibit opposite effects on the surface concentration of cerium; while zirconium promotes the formation of cerium-rich surfaces, yttrium hinders the accumulation of cerium on the surface. For experiments in tight contact between soot and catalyst, all the Ce_1−xY_xO₂ catalysts are more active than bare CeO₂, and Ce_0.99Y_0.01O₂ is the most active catalyst. The benefit of yttrium doping in catalytic activity of ceria can be related to two facts: (i) the Y³⁺ surface enrichment hinders crystallite growth; (ii) the surface segregation of Y³⁺ promotes oxygen vacancies creation. High yttrium loading (x = 0.12) is less effective than low dosage (x = 0.01) because yttrium is mainly accumulated at the surface of the particles and hinders the participation of cerium in the soot oxidation reaction, which is the active component. For the mixed oxides with formulation Ce_0.85−xZr_0.15Y_xO₂ (operating in tight contact) the effect of zirconium on the catalytic activity prevails with respect to that of yttrium. For experiments in loose contact between soot and catalyst, the catalytic activity depends on their BET surface area, and the catalysts Ce_0.85−xZr_0.15Y_xO₂ (BET = 10–13 m²/g) are more active than the catalysts Ce_1−xY_xO₂ (BET = 2–3 m²/g). In the loose contact mode, the yttrium doping and loading have a minor or null affect on the activity, and the stabilising effect of the BET area due to zirconium doping prevails.     

铈锆比对低贵金属Pt＋Rh/Ce0.3＋xZr0.6－xY0.1O1.95＋Al2O3三效催化剂性能的影响

用共沉淀法制得一系列铈锆比不同的Ce_0.3＋xZr_0.6－xY_0.1O_1.95储氧材料, 并用于制备了一系列低贵金属Pt＋Rh/Ce_0.3＋xZr_0.6－xY_0.1O_1.95＋Al₂O₃三效催化剂. 用比表面、程序升温还原以及X射线衍射对该系列催化剂进行表征, 结果发现, 催化剂的活性与催化剂中贵金属的还原性能密切相关, 低铈储氧材料比高铈储氧材料更有利于促进贵金属还原, 因而含低铈储氧材料催化剂的活性明显优于含高铈储氧材料催化剂的活性, Pt＋Rh/Ce_0.35Zr_0.55Y_0.1O_1.95＋Al₂O₃的活性最佳, 对HC, CO和NO的起燃温度最低分别为: 235, 175, 200 ℃. 样品经1000 ℃水热老化之后, 贵金属Pt被烧结而发生迁移, 使得催化剂的活性及还原性能变差, 含低铈材料的催化剂的抗老化性能优于含高铈材料的催化剂, 其中Pt＋Rh/Ce_0.35Zr_0.55Y_0.1O_1.95＋Al₂O₃的抗老化性能最好.     

General and facile synthesis of ceria-based solid solution nanocrystals and their catalytic properties

Uniform Ce_1−xZr_xO₂ (x=0.2–0.8) nanocrystals with ultra-small size were synthesized through a thermolysis process, facilitated by the initial formation of precursor (hydrated (Ce,Zr)-hydroxides) at low temperature. TEM, XRD, EDAX, and Raman spectra were employed to study the formation of the solid solutions with various Ce/Zr ratios. Ultraviolet–visible (UV–vis) spectra showed that the ratios of Ce³⁺ to Ce⁴⁺ in both surface and bulk for the as-prepared Ce_1−xZr_xO₂ nanocrystals increased with the zirconium content x. The well-distributed Zr and Ce in the hydrated (Ce,Zr)-hydroxides before their thermolysis became the crucial factor for the structural homogeneity of the products. In addition, this strategy was extended to the synthesis of Ce_1−xGd_xO_1−x/2, Ce_1−xSm_xO_1−x/2, and Ce_1−xSn_xO₂ solid solutions. Catalytic measurements indicated that the ceria-based catalysts were active for CO oxidation at temperatures beyond 250 °C and the sequence of catalytic activity was Ce_0.5Zr_0.5O₂>Ce_0.8Zr_0.2O₂>Ce_0.2Zr_0.8O₂>Ce_0.5Sm_0.5O_1.75.     

Pt/Ce0.6Zr0.4O2催化剂催化氧化碳烟过程中活性氧对NO-NO2循环及表面含氧物种的分解作用简

通过在Ce_0.6Zr_0.4O₂载体上浸渍Pt（NO₃）₂制得Pt/Ce_0.6Zr_0.4O₂催化剂,该催化剂在松散接触条件下,于NO+O₂或O₂气氛中均表现出比Pt/Al₂O₃更好的碳烟氧化性能. 进一步研究表明,Pt/Ce_0.6Zr_0.4O₂催化剂中的Pt 与Ce_0.6Zr_0.4O₂存在相互作用,使得催化剂在一定温度范围内对活性氧的利用率大为提高,从而促进了气氛中NO↔NO₂的循环,乃至碳烟与NO₂的反应和碳烟表面含氧中间物种的生成;更重要的是,这部分活性氧本身可加速含氧中间物种的分解. 因此,在NO + O₂的气氛中,Pt/Ce_0.6Zr_0.4O₂催化剂的碳烟起燃温度比Pt/Al₂O₃降低了34 ℃.     

Ce4+替代Pu4+的模拟固化体(Gd1-xCex)2Zr2O7+x的合成及结构演变

Gd₂Zr₂O₇中Gd具有很大的中子吸收截面, 其烧绿石结构-缺陷萤石结构的转变能较低, 使其成为理想的核废料固化基材. 使用硝酸盐为原料, 添加少量NaF作助熔剂, 在较低温度下(和传统高温固相反应相比), 合成了烧绿石型Gd₂Zr₂O₇. 以Ce⁴⁺模拟Pu⁴⁺, 研究了Gd₂Zr₂O₇对锕系核素的固化, 并合成了系列模拟固化体(Gd_1-xCe_x)₂Zr₂O_7+x (0≤x≤0.6). 采用粉末X射线衍射(XRD)对系列样品进行了表征. 结果表明: 随着x值的增大,样品从烧绿石结构向缺陷萤石结构转变, 且晶胞大小基本保持恒定, 但当x=0.6时, 衍射峰明显宽化, 晶格畸变比较严重, 晶格稳定性降低. 当x=1时, 即用Ce⁴⁺完全取代Gd³⁺进行合成, 不能得到Ce₂Zr₂O₈, 产物发生了相分离, 为四方结构的(Zr_0.88Ce_0.12)O₂和萤石结构的(Ce_0.75Zr_0.25)O₂的混合物. 模拟固化体的浸出率测试表明: 当x≤0.2时, 各元素浸出率均很低, 但当x≥0.4时, 各元素的浸出率明显升高, 说明以Gd₂Zr₂O₇作为固化Pu⁴⁺的基材, Pu⁴⁺掺入量不宜高于40%.     

The Role of Pd2+/Pd0 in Hydrogenation by [Pd(2‐pymo)2]n: An X‐ray Absorption and IR Spectroscopic Study

The metal–organic framework (MOF) [Pd(2‐pymo)₂]_n (2‐pymo=2‐pyrimidinolate) was used as catalyst in the hydrogenation of 1‐octene. During catalytic hydrogenation, the changes at the metal nodes and linkers of the MOF were investigated by in situ X‐ray absorption spectroscopy (XAS) and IR spectroscopy. With the help of extended X‐ray absorption fine structure and X‐ray absorption near edge structure data, Quick‐XAS, and IR spectroscopy, detailed insights into the catalytic relevance of Pd²⁺/Pd⁰ in the hydrogenation of 1‐octene could be achieved. Shortly after exposure of the catalyst to H₂ and simultaneously with the hydrogenation of 1‐octene, the aromatic rings of the linker molecules are hydrogenated rapidly. Up to this point, the MOF structure remained intact. After completion of linker hydrogenation, the linkers were also protonated. When half of the linker molecules were protonated, the onset of reduction of the Pd²⁺ centers to Pd⁰ was observed and the hydrogenation activity decreased, followed by fast reduction of the palladium centers and collapse of the MOF structure. Major fractions of Pd⁰ are only observed when the hydrogenation of 1‐octene is almost finished. Consequently, the Pd²⁺ nodes of the MOF [Pd(2‐pymo)₂]_n are identified as active centers in the hydrogenation of 1‐octene.     

Nitrides with Inverse K2[NiF4] Structure: (R1–xCa3+xN1–x/3)Bi2 with R = Rare‐Earth Metal

The novel nitrides (R_1–xCa_3+xN_1–x/3)Bi₂ (with R = La, Ce, Pr) crystallize in the K₂[NiF₄] structure type (I4/mmm, No. 139, Z = 2). Samples (La_1–xCa_3+xN_1–x/3)Bi₂ with x = 0.10, 0.05, 0.00, (Ce_1–xCa_3+xN_1–x/3)Bi₂ with x = 0.30, and (PrCa₃N)Bi₂ were obtained as single phase microcrystalline powders according to X‐ray diffraction and the crystal structure details were derived from Rietveld refinements based on X‐ray and neutron diffraction powder patterns. A partial order of R³⁺/Ca²⁺ on two crystallographic sites is governed by different ionic radii and charges. (La_1–xCa_3+xN_1–x/3)Bi₂ and (Ce_1–xCa_3+xN_1–x/3)Bi₂ exhibit small homogeneity ranges and typically a nitrogen deficiency. In contrast, for (PrCa₃N)Bi₂ no indications for a significant homogeneity range or deficiency of nitrogen was observed. (La_1–xCa_3+xN_1–x/3)Bi₂ with x = 0.05 is a diamagnet. X‐ray absorption spectroscopy at the CeL₃‐edge as well as magnetic susceptibility measurements evidence that (Ce_1–xCa_3+xN_1–x/3)Bi₂ with x = 0.30 contains Ce³⁺ in the 4f¹ configuration. According to electrical resistivity data, samples from all three systems are heavily doped semiconductors.     

Preparation and Characterization of Mesoporous Ce0.5Zr0.5O2 Mixed Oxide

Mesoporous （MSU） Ce0.5Zr0.5O2 mixed oxide with a high specific surface area has been synthesized under weak acidic condition in the presence of an anionic surfactant, sodium dodecylbenzenesulfonate. The effect of the pH value on the formation of mesostructure and the thermal stability of the material has been evaluated. The products were characterized by transmission electron microscopy, powder X-ray diffraction and nitrogen adsorption-desorption measurements. The results showed that the as-prepared Ce0.5Zr0.5O2 mixed oxide possessed a specific surface area of 163.3 m^2·g^-1, which had a cubic fluorite-type structure and possessed specific surface areas of 148.4 and 62.4 m^2·g^-1 after calcination at 500 and 800 ℃ for 2 h, respectively. The material showed excellent thermal stability.     

Preparation and Characterization of Mg‐Zr Mixed Oxide Aerogels and Their Application as Aldol Condensation Catalysts

A series of Mg‐Zr mixed oxides with different nominal Mg/ (Mg+Zr) atomic ratios, namely 0, 0.1, 0.2, 0.4, 0.85, and 1, is prepared by alcogel methodology and fundamental insights into the phases obtained and resulting active sites are studied. Characterization is performed by X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, N₂ adsorption–desorption isotherms, and thermal and chemical analysis. Cubic Mg_xZr_1?xO_2?x solid solution, which results from the dissolution of Mg²⁺ cations within the cubic ZrO₂ structure, is the main phase detected for the solids with theoretical Mg/ (Mg+Zr) atomic ratio ≤0.4. In contrast, the cubic periclase (c‐MgO) phase derived from hydroxynitrates or hydroxy precursors predominates in the solid with Mg/(Mg+Zr)=0.85. c‐MgO is also incipiently detected in samples with Mg/(Mg+Zr)=0.2 and 0.4, but in these solids the c‐MgO phase mostly arises from the segregation of Mg atoms out of the alcogel‐derived c‐Mg_xZr_1?xO_2?x phase during the calcination process, and therefore the species c‐MgO and c‐Mg_xZr_1?xO_2?x are in close contact. Regarding the intrinsic activity in furfural–acetone aldol condensation in the aqueous phase, these Mg? O? Zr sites located at the interface between c‐Mg_xZr_1?xO_2?x and segregated c‐MgO display a much larger intrinsic activity than the other noninterface sites that are present in these catalysts: Mg? O? Mg sites on c‐MgO and Mg? O? Zr sites on c‐Mg_xZr_1?xO_2?x. The very active Mg? O? Zr sites rapidly deactivate in the furfural–acetone condensation due to the leaching of active phases, deposition of heavy hydrocarbonaceous compounds, and hydration of the c‐MgO phase. Nonetheless, these Mg‐Zr materials with very high specific surface areas would be suitable solid catalysts for other relevant reactions catalyzed by strong basic sites in nonaqueous environments.     

Sulfur‐Modified Oxygen Vacancies in Iron–Cobalt Oxide Nanosheets: Enabling Extremely High Activity of the Oxygen Evolution Reaction to Achieve the Industrial Water Splitting Benchmark

The oxygen vacancies of defective iron–cobalt oxide (FeCoO_x‐Vo) nanosheets are modified by the homogeneously distributed sulfur (S) atoms. S atoms can not only effectively stabilize oxygen vacancies (Vo), but also form the Co?S coordination with Co active site in the Vo, which can modulate the electronic structure of the active site, enabling FeCoO_x‐Vo‐S to exhibit much superior OER activity. FeCoO_x‐Vo‐S exhibits a mass activity of 2440.0 A g^?1 at 1.5 V vs. RHE in 1.0 m KOH, 25.4 times higher than that of RuO₂. The Tafel slope is as low as 21.0 mV dec^?1, indicative of its excellent charge transfer rate. When FeCoO_x‐Vo‐S (anode catalyst) is paired with the defective CoP₃/Ni₂P (cathode catalyst) for overall water splitting, current densities of as high as 249.0 mA cm^?2 and 406.0 mA cm^?2 at a cell voltage of 2.0 V and 2.3 V, respectively, can be achieved.     

XRD and UV-Vis diffuse reflectance analysis of CeO2-ZrO2 solid solutions synthesized by combustion method

A series of ceria-incorporated zirconia (Ce_1−xZr_xO₂,x = 0 to 1) solid solutions were prepared by employing the solution combustion synthesis route. The products were characterized by XRD and UV-Vis-NIR diffuse reflectance spectroscopy. The materials are crystalline in nature and the lattice parameters of the solid solution series follow Vegard’s law. Diffuse reflectance spectra of the solid solutions in the UV region show two intense bands at 250 and 297 nm which are assigned respectively to Ce³⁺ ← O²⁻and Ce⁴⁺ ← O²⁻ charge transfer transitions. The two vibrational bands in 6960 cm⁻¹ and 5168 cm⁻¹ in the NIR region indicate the presence of surface hydroxyl groups on these materials.