Unveiling Direct Electrochemical Oxidation of Methane at the Ceria/Gas Interface

Solid oxide fuel cells (SOFCs) stand out in sustainable energy systems for their unique ability to efficiently utilize hydrocarbon fuels, particularly those from carbon-neutral sources. CeO2-δ (ceria) based oxides embedded in SOFCs are recognized for their critical role in managing hydrocarbon activation and carbon coking. However, even for the simplest hydrocarbon molecule, CH4, the mechanism of electrochemical oxidation at the ceria/gas interface is not well understood and the capability of ceria to electrochemically oxidize methane remains a topic of debate. This lack of clarity stems from the intricate design of standard metal/oxide composite electrodes and the complex nature of electrode reactions involving multiple chemical and electrochemical steps. This study presents a Sm-doped ceria thin-film model cell that selectively monitors CH4 direct-electro-oxidation on the ceria surface. Using impedance spectroscopy, operando X-ray photoelectron spectroscopy, and density functional theory, it is unveiled that ceria surfaces facilitate C─H bond cleavage and that H2O formation is key in determining the overall reaction rate at the electrode. These insights effectively address the longstanding debate regarding the direct utilization of CH4 in SOFCs. Moreover, these findings pave the way for an optimized electrode design strategy, essential for developing high-performance, environmentally sustainable fuel cells.

A sustainable approach for selective recovery of lithium from cathode materials of spent lithium-ion batteries by induced phase transition

Recycling of spent lithium-ion batteries (LIBs) has attracted widespread attention because of their dual attributes to environmental protection and resource conservation. Utilization of strong corrosive acids is currently the preferred way to recover valuable metals from spent LIBs, but the extensive use of chemical reagents can pose serious environmental risks. Herein, this research proposes a green process for selective recovery of lithium using the material of spent LIBs itself without adding exogenous reagents, mechanochemistry induced phase transition. The leaching efficiency of Li can reach 94% by employing the copper foil separated from spent LIBs as the co-grinding additive during the mechanochemical reaction process. Then, the high value LiOH·H₂O can be prepared through direct evaporation and crystallization without adding any precipitant. Meanwhile, cobalt is almost remained in the leaching residue which can be recovered through a step-by-step separation process. XRD, XPS, and SEM-EDS characterizations show that LiCoO₂ and copper foil are transformed into the soluble Li₂O, and insoluble CuO and CoO under the mechanical force. Finally, the soluble Li₂O is dissolved in water to prepare the LiOH solution, and the insoluble CuO and CoO are transformed into Cu₂O and Co(OH)₂. On the basis of the experimental investigation, it is proven that the proposed process is suitable for selectively recovering Li from all types of cathode materials without generating salty wastewater or introducing chemical reagents. Thus, the proposed approach can ensure the efficient recovery of valuable metals from spent LIBs while avoiding the potential threat to the environment and human health.

Surface Modification of an Absorbable Bimodal Fe-Mn-Ag Alloy by Nitrogen Plasma Immersion Ion Implantation

Recently, Fe-Mn-based alloys have been increasingly catching the attention of the scientific community, because of their tunable and outstanding mechanical properties, and suitable degradation behavior for biomedical applications. In spite of these assets, their corrosion rate (CR) is, in general, too low to satisfy the requirements that need to be met for cardiovascular device applications, such as stents. In fact, the CR is not always the same for all of the degradation stages of the material, and in addition, a finely tuned release rate, especially during the first steps of the corrosion pattern, is often demanded. In this work, a resorbable bimodal multi-phase alloy Fe-3Mn-1Ag was designed by mechanical alloying and spark plasma sintering (SPS) to accelerate the corrosion rate. The presence of several phases, for example α-Fe, α-Mn, γ-FeMn and Ag, provided the material with excellent mechanical properties (tensile strength UTS = 722 MPa, tensile strain A = 38%) and a higher corrosion rate (CR = 3.2 ± 0.2 mm/year). However, higher corrosion rates, associated with an increased release of degradation elements, could also raise toxicity concerns, especially at the beginning of the corrosion pattern. In this study, The focus of the present work was the control of the CR by surface modification, with nitrogen plasma immersion ion implantation (N-PIII) treatment that was applied to mechanically polished (MP) samples. This plasma treatment (PT) improved the corrosion resistance of the material, assessed by static degradation immersion tests (SDITs), especially during the first degradation stages. Twenty-eight days later, the degradation rate reached the same value of the MP condition. Nitrogen compounds on the surface of the substrate played an important role in the corrosion mechanism and corrosion product formation. The degradation analysis was carried out also by potentiodynamic tests in modified Hanks' balanced salt solution (MHBSS), and Dulbecco's phosphate buffered saline solution (DPBSS). The corrosion rate was higher in MHBSS for both conditions. However, there was no significant difference between the corrosion rate of the PT in DPBSS (CR = 1.9 ± 0.6 mm/year) and in MHBSS (CR = 2 ± 1.4 mm/year). The cell viability was assessed with human vein endothelial cells (HUVECs) via an indirect metabolic activity test (MTT assay). Due to the lower ion release of the PT condition, the cell viability increased significantly. Thus, nitrogen implantation can control the in vitro corrosion rate starting from the very first stage of the implantation, improving cell viability.

The Extent of Platinum-Induced Hydrogen Spillover on Cerium Dioxide

Hydrogen spillover from metal nanoparticles to oxides is an essential process in hydrogenation catalysis and other applications such as hydrogen storage. It is important to understand how far this process is reaching over the surface of the oxide. Here, we present a combination of advanced sample fabrication of a model system and in situ X-ray photoelectron spectroscopy to disentangle local and far-reaching effects of hydrogen spillover in a platinum-ceria catalyst. At low temperatures (25-100 °C and 1 mbar H2) surface O-H formed by hydrogen spillover on the whole ceria surface extending microns away from the platinum, leading to a reduction of Ce4+ to Ce3+. This process and structures were strongly temperature dependent. At temperatures above 150 °C (at 1 mbar H2), O-H partially disappeared from the surface due to its decreasing thermodynamic stability. This resulted in a ceria reoxidation. Higher hydrogen pressures are likely to shift these transition temperatures upward due to the increasing chemical potential. The findings reveal that on a catalyst containing a structure capable to promote spillover, hydrogen can affect the whole catalyst surface and be involved in catalysis and restructuring.

Bixbyite-type Ln2O3 as promoters of metallic Ni for alkaline electrocatalytic hydrogen evolution

The active-site density, intrinsic activity, and durability of Ni-based catalysts are critical to their application in industrial alkaline water electrolysis. This work develops a kind of promoters, the bixbyite-type lanthanide metal sesquioxides (Ln₂O₃), which can be implanted into metallic Ni by selective high-temperature reduction to achieve highly efficient Ni/Ln₂O₃ hybrid electrocatalysts toward hydrogen evolution reaction. The screened Ni/Yb₂O₃ catalyst shows the low overpotential (20.0 mV at 10 mA cm⁻²), low Tafel slope (44.6 mV dec⁻¹), and excellent long-term durability (360 h at 500 mA cm⁻²), significantly outperforming the metallic Ni and benchmark Pt/C catalysts. The remarkable hydrogen evolution activity and stability of Ni/Yb₂O₃ are attributed to that the Yb₂O₃ promoter with high oxophilicity and thermodynamic stability can greatly enlarge the active-site density, reduce the energy barrier of water dissociation, optimize the free energy of hydrogen adsorption, and avoid the oxidation corrosion of Ni.

While renewable H₂ evolution will require inexpensive, abundant catalysts, non-noble metals typically show relatively low activities. Here, authors examine lanthanide metal sesquioxide doped metallic Ni and show efficient, stable performances for alkaline H₂ evolution electrocatalysis.

Structure and reactivity of model CeO2surfaces

As a key component in many industrial heterogeneous catalysts, the surface structure and reactivity of ceria, CeO₂, has attracted a lot of attention. In this topical review we discuss some of the approaches taken to form a deeper understanding of the surface physics and chemistry of this important and interesting material. In particular, we focus on the preparation of ultrathin ceria films, nanostructures and supported metal nanoparticles. Cutting-edge microscopic and spectroscopic experimental techniques are highlighted which can probe the behaviour of oxygen species and atomic defects on these model surfaces.

Redox-mediated C-C bond scission in alcohols adsorbed on CeO2-xthin films

The decomposition mechanisms of ethanol and ethylene glycol on well-ordered stoichiometric CeO₂(111) and partially reduced CeO_2-x(111) films were investigated by means of synchrotron radiation photoelectron spectroscopy, resonant photoemission spectroscopy, and temperature programmed desorption. Both alcohols partially deprotonate upon adsorption at 150 K and subsequent annealing yielding stable ethoxy and ethylenedioxy species. The C-C bond scission in both ethoxy and ethylenedioxy species on stoichiometric CeO₂(111) involves formation of acetaldehyde-like intermediates and yields CO and CO₂accompanied by desorption of acetaldehyde, H₂O, and H₂. This decomposition pathway leads to the formation of oxygen vacancies. In the presence of oxygen vacancies, C-O bond scission in ethoxy species yields C₂H₄. In contrast, C-C bond scission in ethylenedioxy species on the partially reduced CeO_2-x(111) is favored with respect to C-O bond scission and yields methanol, formaldehyde, and CO accompanied by the desorption of H₂O and H₂. Still, scission of C-O bonds on both sides of the ethylenedioxy species yields minor amounts of accompanying C₂H₄and C₂H₂. C-O bond scission is coupled with a partial recovery of the lattice oxygen in competition with its removal in the form of water.

Praseodymia–titania mixed oxide supported gold as efficient water gas shift catalyst: modulated by the mixing ratio of oxides

Modulating the active sites for controllable tuning of the catalytic activity has been the goal of much research, however, this remains challenging. The O vacancy is well known as an active site in reducible oxides. To modify the activity of O vacancies in praseodymia, we synthesized a series of praseodymia–titania mixed oxides. Varying the Pr : Ti mole ratio (2 : 1, 1 : 2, 1 : 1, 1 : 4) allows us to control the electronic interactions between Au, Pr and Ti cations and the local chemical environment of the O vacancies. These effects have been studied study by X-ray photoelectron spectroscopy (XPS), CO diffuse reflectance Fourier transform infrared spectroscopy (CO-DRIFTS) and temperature-programmed reduction (CO-TPR, H₂-TPR). The water gas shift reaction (WGSR) was used as a benchmark reaction to test the catalytic performance of different praseodymia–titania supported Au. Among them, Au/Pr₁Ti₂O_x was identified to exhibit the highest activity, with a CO conversion of 75% at 300 °C, which is about 3.7 times that of Au/TiO₂ and Au/PrO_x. The Au/Pr₁Ti₂O_x also exhibited excellent stability, with the conversion after 40 h time-on-stream at 300 °C still being 67%. An optimal ratio of Pr content (Pr : Ti 1 : 2) is necessary for improving the surface oxygen mobility and oxygen exchange capability, a higher Pr content leads to more O vacancies, however with lower activity. This study presents a new route for modulating the active defect sites in mixed oxides which could also be extended to other heterogeneous catalysis systems.

Schematic illustration of H₂O activation on the Pr-TiO_x support and the following reaction with CO in the Au–oxide interface.

Spatially resolved investigation into the coke formation and chemical states of nickel during autothermal reforming of acetic acid over Ni/CeO2-ZrO2 catalysts

Autothermal reforming (ATR) is a viable option for reducing coke formation and energy consumption in hydrogen production processes. The space-resolved ATR of acetic acid as model compound over Ni/Ce0.75Zr0.25O2 catalyst...

The Effects of Ce and W Promoters on the Performance of Alumina-Supported Nickel Catalysts in CO2 Methanation Reaction

The influence of Ce and W promoters on the performance of alumina-supported nickel catalysts in the CO2 methanation reaction was investigated. The catalysts were obtained by the co-impregnation method. Nitrogen low-temperature adsorption, temperature-programmed reduction, hydrogen desorption, transmission electron microscopy, X-ray diffraction, and photoelectron spectroscopy studies were used for catalyst characterization. An introduction of Ce and W promoters (1–5 wt %) led to the decrease in mean Ni crystallite size. Gradual increase in the active surface area was observed only for Ce-promoted catalysts. The increase in CO2 conversion in methanation reaction at low-reaction temperatures carried out over Ce-promoted catalysts was attributed to the increase in the active surface area and changes in the redox properties. The introduction of small amounts of tungsten led to an increase in the activity of catalysts, although a decrease in the active surface area was observed. Quasi in situ XPS studies revealed changes in the oxidation state of tungsten under CO2 methanation reaction conditions, indicating the participation of redox promoter changes in the course of surface reactions, leading to an improvement in the activity of the catalyst.

Converting spent lithium cobalt oxide battery cathode materials into high-value products via a mechanochemical extraction and thermal reduction route

This study innovatively combines mechanochemistry and high-temperature thermal reduction to achieve the recovery of valuable metals from spent LIBs. First, under the action of mechanical force, the crystal structure of lithium cobalt oxide (LiCoO₂) found in the cathode materials of spent LIBs was destroyed and converted into lithium carbonate (Li₂CO₃) and Li-free residue (C/Co₃O₄) using dry ice as a co-grinding reagent. The optimum Li₂CO₃ recovery conditions were determined to be as follows: a ratio of dry ice: LiCoO₂ powder mass of 20:1; a rotation speed of 700 rpm, and a reaction time of 1.5 h. With these conditions the maximum percentage of Li₂CO₃ recovered was 95.04 wt%. The Co₃O₄ in Li-free residue was reduced to a high-value Co⁰ product via a high-temperature (800 °C) heat treatment. Gibbs free energy analysis confirmed that the carbon in the Li-free residue could be used as a self-reducing reagent for the thermal reduction of Co₃O₄. The reactants and products of each step were characterized by XRD, FT-IR, XPS and SEM techniques. The green route for recycling spent LIBs that this study proposes realizes the green and cost-effective conversion of LiCoO₂ to high-value products, which may become an outstanding example of recycling spent LIBs.

Deactivation-free ethanol steam reforming at nickel-tipped carbon filaments

Ni based catalysts have been widely studied for H2 production due to the ability of Ni to break C-C and C-H bonds. In this work, we study inverse catalysts prepared by well-controlled sub-monolayer deposition of CeO2 nanocubes onto Ni thin films for ethanol steam reforming (ESR). Results show that controlling the coverage of CeO2 nanocubes on Ni enhances H2 production by more than an order of magnitude compared to pure Ni. Contrary to the idea that C deposits must be continuously oxidized for sustained H2 production, the surface of the most active catalysts show significant C deposition, yet no deactivation is observed. HAADF-STEM analysis reveals the formation of carbon filaments (CFILs), which propel Ni particles upward at the filament tips via a catalytic tip growth mechanism, resulting in a Ni@CFIL active phase for ESR. Near-ambient pressure XPS indicates that the Ni@CFIL active phase forms as a result of C gradients at the interface between regions of pure Ni metal and domains of closely packed CeO2 nanocubes. These results show that the mesoscale morphology of deposited CeO2 nanocubes is responsible for templating the formation of a Ni@CFIL catalyst, which resists deactivation leading to highly active and stable H2 production from ethanol.

Heterogeneous Non-noble Catalyst for Highly Selective Production of Linear α-Olefins from Fatty Acids: A Discovery of NiFe/C

Catalytic deoxygenation of even-numbered fatty acids into odd-chain linear α-olefins (LAOs) has emerged as a complementary strategy to oligomerization of ethylene, which only affords even-chain LAOs. Although enzymes and homogeneous catalysts have shown promising potential for this application, industrial production of LAOs through these catalytic systems is still very difficult to accomplish to date. A recent breakthrough involves the use of an expensive noble-metal catalyst, Pd/C, through a phosphine ligands-assisted method for LAOs production from fatty acid conversion. This study presents a unique, cost-friendly, non-noble bimetallic NiFe/C catalyst for highly selective LAOs production from fatty acids through decarbonylative dehydration. In the presence of acetic anhydride and phosphine ligand, a remarkable improvement in the yield of 1-heptadecene from the conversion of stearic acid was found over the supported bimetallic catalyst (NiFe/C) as compared to corresponding monometallic counterparts (Ni/C and Fe/C). Through optimization of the reaction conditions, a 70.1 % heptadecene yield with selectivity to 1-heptadecene as high as 92.8 % could be achieved over the bimetallic catalyst at just 190 °C. This unique bimetallic NiFe/C catalyst is composed of NiFe alloy in the material bulk phase and a surface mixture of NiFe alloy and oxidized NiFe^δ+ species, which offer a synergized contribution towards decarbonylative dehydration of stearic acid for 1-heptadecene production.

Present and new frontiers in materials research by ambient pressure x-ray photoelectron spectroscopy

In this topical review we catagorise all ambient pressure x-ray photoelectron spectroscopy publications that have appeared between the 1970s and the end of 2018 according to their scientific field. We find that catalysis, surface science and materials science are predominant, while, for example, electrocatalysis and thin film growth are emerging. All catalysis publications that we could identify are cited, and selected case stories with increasing complexity in terms of surface structure or chemical reaction are discussed. For thin film growth we discuss recent examples from chemical vapour deposition and atomic layer deposition. Finally, we also discuss current frontiers of ambient pressure x-ray photoelectron spectroscopy research, indicating some directions of future development of the field.

Controllable design, synthesis and characterization of nanostructured rare earth metal oxides

Rare earth metal oxide nanomaterials have drawn much attention in recent decades due to their unique properties and promising applications in catalysis, chemical and biological sensing, separation, and optical devices. Because of the strong structure–property correlation, controllable synthesis of nanomaterials with desired properties has long been the most important topic in nanoscience and nanotechnology and still maintains a grand challenge. A variety of methods, involving chemical, physical, and hybrid method, have been developed to precisely control nanomaterials, including size, shape, dimensionality, crystal structure, composition, and homogeneity. These nanostructural parameters play essential roles in determining the final properties of functional nanomaterials. Full understanding of nanomaterial properties through characterization is vital in elucidating the fundamental principles in synthesis and applications. It allows researchers to discover the correlations between the reaction parameters and nanomaterial properties, offers valuable insights in improving synthetic routes, and provokes new design strategies for nanostructures. In application systems, it extrapolates the structure–activity relationship and reaction mechanism and helps to establish quality model for similar reaction processes. The purpose of this chapter is to provide a comprehensive overview and a practical guide of rare earth oxide nanomaterial design and characterization, with special focus on the well-established synthetic methods and the conventional and advanced analytical techniques. This chapter addresses each synthetic method with its advantages and certain disadvantages, and specifically provides synthetic strategies, typical procedures and features of resulting nanomaterials for the widely-used chemical methods, such as hydrothermal, solvothermal, sol–gel, co-precipitation, thermal decomposition, etc. For the nanomaterial characterization, a practical guide for each technique is addressed, including working principle, applications, materials requirements, experimental design and data analysis. In particular, electron and force microscopy are illuminated for their powerful functions in determining size, shape, and crystal structure, while X-ray based techniques are discussed for crystalline, electronic, and atomic structural determination for oxide nanomaterials. Additionally, the advanced characterization methodologies of synchrotron-based techniques and in situ methods are included. These non-traditional methods become more and more popular because of their capabilities of offering unusual nanostructural information, short experiment time, and in-depth problem solution.

Graphical Abstract:

Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review

The development of better catalysts is a passionate topic at the forefront of modern science, where operando techniques are necessary to identify the nature of the active sites. The surface of a solid catalyst is dynamic and dependent on the reaction environment and, therefore, the catalytic active sites may only be formed under specific reaction conditions and may not be stable either in air or under high vacuum conditions. The identification of the active sites and the understanding of their behaviour are essential information towards a rational catalyst design. One of the most powerful operando techniques for the study of active sites is near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), which is particularly sensitive to the surface and sub-surface of solids. Here we review the use of NAP-XPS for the study of ceria-based catalysts, widely used in a large number of industrial processes due to their excellent oxygen storage capacity and well-established redox properties.

Differential pulse voltammetric determination of the carcinogenic diamine 4,4'-oxydianiline by electrochemical preconcentration on a MoS2 based sensor

An electrochemical sensor for the carcinogen 4,4'-oxydianiline (Oxy) is described. The method is based on the ability of MoS₂ nanosheets to preconcentrate Oxy. A glassy carbon electrode (GCE) was covered, by drop-casting, with MoS₂ nanosheets that were obtained by exfoliation. X-Ray photoemission spectroscopy indicates that Oxy accumulates on the MoS₂ nanosheets through an electropolymerization process similar to that reported for aniline. Both electrochemical impedance spectroscopy and atomic force microscopy were used to characterize the electrode surface at the different stages of device fabrication. Employing the current measured at +0.27 V vs. Ag/AgCl after Oxy adsorption, the modified GCE enables the voltammetric detection of Oxy at 80 nM levels with relative errors and relative standard deviations of <8.3 and <5.6%, respectively, at all the concentrations studied. The method was applied to the selective determination of Oxy in spiked river water samples. Very good selectivity and recoveries of around 95% in average are found. Graphical abstractSchematic representation of 4,4-oxydianiline electrochemical polymerization and preconcentration onto molybdenum disulfide nanosheets for the diamine determination in river waters.

Morphology effects on surface chemical properties and lattice defects of Cu/CeO2 catalysts applied for low-temperature CO oxidation

Here, we synthesized a series of Cu/CeO2 catalysts with different morphology and size, including Cu/CeO2 nanospheres (Cu/CeO2-S), Cu/CeO2 nanoparticles (Cu/CeO2-P), Cu/CeO2 nanorods (Cu/CeO2-R) and flower-like Cu/CeO2 microspheres (Cu/CeO2-F) to systematically explore the structure-activity relationship in CO oxidation. Crucially, the effect of morphology, crystal size, Ce4+/Ce3+ species, oxygen vacancies derived from the removal of lattice oxygen (Olatt) species in CeO2 and lattice defect sites on CO activity was revealed through various characterizations. It was clearly discovered that the activity of these catalysts was as follows: Cu/CeO2-R > Cu/CeO2-P > Cu/CeO2-S > Cu/CeO2-F, and the Cu/CeO2-R catalyst preferentially showed the best catalytic performance with a 90% conversion of CO even at 58 °C, owned the smaller particles size of CeO2 and CuO, and exhibited the higher concentration of Olatt species and oxygen vacancies. Besides, it is also verified that the Cu/CeO2-F sample exhibited the larger CeO2 crystal size (17.14 nm), which led to the lower Cu dispersion and CO conversion, even at 121 °C (T90). Most importantly, we discovered that the amount of surface lattice defect sites was positively related to the reaction rate of CO. Simultaneously, DFT calculation also demonstrated that the introduced oxygen vacancies in CeO2 could accelerate the oxidation of CO by the alteration of CO adsorption energy. Therefore, the morphology, the crystal size, the content of oxygen vacancies, as well as lattice defects of Cu/CeO2 catalyst might work together for CO oxidation reaction.

A mini review of in situ near-ambient pressure XPS studies on non-noble, late transition metal catalysts

The rich surface chemistry of Fe, Co, Ni and Cu during heterogeneous catalytic reactions from the perspective of NAP-XPS studies.

Effect of ZnO on acid–base properties and catalytic performances of ZnO/ZrO2–SiO2 catalysts in 1,3-butadiene production from ethanol–water mixture

The effect of ZnO and the preparation method of ZnO/ZrO₂–SiO₂ catalysts on their acid–base properties and catalytic performances in the conversion of diluted ethanol mixtures into 1,3-butadiene (BD) is presented.

Thermal reduction of ceria nanostructures on rhodium(111) and re-oxidation by CO2

The thermal reduction of cerium oxide nanostructures deposited on a rhodium(111) single crystal surface and the re-oxidation of the structures by exposure to CO2 were investigated. Two samples are compared: a rhodium surface covered to ≈60% by one to two O-Ce-O trilayer high islands and a surface covered to ≈65% by islands of four O-Ce-O trilayer thickness. Two main results stand out: (1) the thin islands reduce at a lower temperature (870-890 K) and very close to Ce2O3, while the thicker islands need higher temperature for reduction and only reduce to about CeO1.63 at a maximum temperature of 920 K. (2) Ceria is re-oxidized by CO2. The rhodium surface promotes the re-oxidation by splitting the CO2 and thus providing atomic oxygen. The process shows a clear temperature dependence. The maximum oxidation state of the oxide reached by re-oxidation with CO2 differs for the two samples, showing that the thinner structures require a higher temperature for re-oxidation with CO2. Adsorbed carbon species, potentially blocking reactive sites, desorb from both samples at the same temperature and cannot be the sole origin for the observed differences. Instead, an intrinsic property of the differently sized CeOx islands must be at the origin of the observed temperature dependence of the re-oxidation by CO2.

Growth and structure of ultrathin praseodymium oxide layers on ruthenium(0001)

The growth, morphology, structure, and stoichiometry of ultrathin praseodymium oxide layers on Ru(0001) were studied using low-energy electron microscopy and diffraction, photoemission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. At a growth temperature of 760 °C, the oxide is shown to form hexagonally close-packed (A-type) Pr₂O₃(0001) islands that are up to 3 nm high. Depending on the local substrate step density, the islands either adopt a triangular shape on sufficiently large terraces or acquire a trapezoidal shape with the long base aligned along the substrate steps.

New Routes for Refinery of Biogenic Platform Chemicals Catalyzed by Cerium Oxide-supported Ruthenium Nanoparticles in Water

Highly selective hydrogenative carbon-carbon bond scission of biomass-derived platform oxygenates was achieved with a cerium oxide-supported ruthenium nanoparticle catalyst in water. The present catalyst enabled the selective cleavage of carbon-carbon σ bonds adjacent to carboxyl, ester, and hydroxymethyl groups, opening new eight synthetic routes to valuable chemicals from biomass derivatives. The high selectivity for such carbon-carbon bond scission over carbon-oxygen bonds was attributed to the multiple catalytic roles of the Ru nanoparticles assisted by the in situ formed Ce(OH)₃.

Ceria-based model catalysts: fundamental studies on the importance of the metal–ceria interface in CO oxidation, the water–gas shift, CO2 hydrogenation, and methane and alcohol reforming

Model metal/ceria and ceria/metal catalysts have shown to be excellent systems for studying fundamental phenomena linked to the operation of technical catalysts.

The role of metal–support interaction for CO-free hydrogen from low temperature ethanol steam reforming on Rh–Fe catalysts

Effect of metal–support interaction on the generation of Rh–Fe_xO_y active sites is investigated via various in situ techniques.