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Alkyl cyclohexanes were synthesized in high selectivity via a combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3 as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situ during the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.

Hydrogen produced from H2O electrolysis works as an energy carrier and helps to overcome the challenges of intermittent renewable energy sources. At present, no comprehensive environmental impact assessment is available for three commercially H2O electrolysis technologies, namely solid oxide electrolysis cell (SOEC), polymer electrolyte membrane electrolysis cell (PEMEC), and alkaline electrolysis cell (AEC). The study aimed to provide potential environmental impacts of the electrolysis technologies based on life cycle assessment. Among the investigated 16 impact categories, the stage of critical material use of three H2O electrolysis stacks was identified as the hotspot of environmental impacts. The critical materials were stainless steel and nickel from SOEC, platinum and iridium from PEMEC, and nickel from AEC. Life cycle impact results from PEMEC stack were much higher than these from SOEC and AEC stacks, while electricity played a more important role in the life cycle impact of hydrogen production. The sensitivity analysis indicated that the most effective approach to reducing potential impacts would be to reduce critical materials use on the current status of electrolysis technologies.

Regenerated cellulose is a natural, renewable and biodegradable material but is commonly obtained via environmentally hazardous processes. Here, a simple, environmentally friendly route is presented involving rapid coagulation of dissolved cellulose by nontoxic organic carbonates.

The oxidative coupling of methane (OCM) to C2-hydrocarbons (C2H4 and C2H6) is attractive both from fundamental (selective C–H bond activation) and applied viewpoints. The main drawback hindering its commercialization is the low selectivity to C2-hydrocarbons due to their further oxidation to carbon oxides. In this respect, we focused on elucidating fundamentals of the previously reported positive effect of water on the activity and selectivity in the OCM reaction over MnOx-Na2WO4/SiO2 by means of steady-state kinetic and mechanistic tests at ambient pressure as well as temporal analysis of products with sub-millisecond resolution and isotopic tracers in vacuum. The obtained results cannot be rationalized by the earlier developed concepts explaining the role of water in the OCM reaction over this catalyst system. In addition, the selectivity-enhancing water effect was determined for MnOx/SiO2, MnOx/Al2O3, Na2WO4/SiO2, and Na2WO4/Al2O3, as well as SiO2-based materials with supported PbOx, ZrO2, or La2O3. No rate-improving effect was established for MnOx/Al2O3 and ZrO2/SiO2, while positive or negative effects were determined for PbOx/SiO2, MnOx/SiO2, and Na2WO4/SiO2 or La2O3/SiO2 and Na2WO4/Al2O3, respectively. Thus, testing other catalysts in the water presence seems to be promising in view of improving the OCM performance to an industrially attractive level. Owing to the developed protocol for catalyst testing under alternating water-free and water-containing OCM feeds, both reversible and irreversible water effects on the selectivity to C2-hydrocarbons over MnOx-Na2WO4/SiO2 were identified. The irreversible effect was related to water-induced redispersion of MnOx. Mechanistic insights into the reversible rate- and selectivity-improving effects were derived from kinetic analysis of the rates of methane conversion into individual reaction products at different water partial pressures and temperatures. Selectivity–conversion relationships enabled us to understand the specific reaction pathways in the course of the OCM reaction affected by water. Water was established to increase the rates of methane conversion into C2-hydrocarbons, CO, and CO2 with the strongest effect being determined for CO formation. For all the rates, the strength of the positive water effect decreases with an increase in temperature from 750 to 825 °C. In addition to the acceleration of methane conversion, water also helps to transform nonselective molecular-adsorbed oxygen species responsible for the direct oxidation of methane to carbon dioxide.

Environmentally friendly and low-cost catalysts are required for large-scale nonoxidative dehydrogenation of propane to propene (PDH) to replace currently used CrOx- or Pt-based catalysts. This work introduces ZnO-containing ZrO2- or MZrOx-supported (M = Ce, La, Ti or Y) catalysts. The most active materials outperformed the state-of-the-art catalysts with supported CrOx, GaOx, ZnOx, or VOx species as well as bulk ZrO2-based catalysts without ZnO. The space–time yield of propene of 1.25 kgC3H6·kg–1cat·h–1 at a propane conversion of about 30% with a propene selectivity of 95% was obtained over Zn­(4 wt %)/TiZrOx at 550 °C. For deriving key insights into the structure of active sites, reactivity, selectivity, and on-stream stability, the catalysts were characterized by XRD, HRTEM, EDX mapping, XPS, X-ray absorption, CO-TPR, CO2-TPD, NH3-TPD, pyridine-FTIR, operando UV–vis spectroscopy, Raman spectroscopy, TPO, and temporal analysis of products. In contrast with previous reports that used bulk ZrO2-based catalysts without ZnO, coordinatively unsaturated Zr cations are not the main active sites in the ZnO-containing catalysts. Supported ZnOx species were concluded to participate in the PDH reaction. The current X-ray absorption analysis proved that their structure is affected by the type of metal oxide used as a dopant for ZrO2 and by the crystallinity of ZrO2. Isolated tricoordinated Zn2+ species were concluded to show high activity and on-stream stability. Their intrinsic activity is enhanced when TiO2 and ZrO2 coexist in the support or when ZrO2 is promoted by TiO2. This is probably due to accelerating hydrogen formation in the course of the PDH reaction as concluded from temporal analysis of products with sub-millisecond resolution. The results of temperature-programmed oxidation of spent catalysts as well as ex situ Raman and operando UV–vis studies enabled us to conclude that the high on-stream stability of isolated tricoordinated Zn2+ species in the PDH reaction is related to their low ability to form coke. In general, the tendency for coke formation seems to increase with an increase in the degree of ZnOx agglomeration.

Future district heating systems and technologies—also known as fourth-generation district heating—have a potentially important role to play in the green transition of societies. The implementation of fourth-generation district heating involves adjustments in the demand side to allow for low temperature supply. In order to facilitate such changes, district heating supply companies have in recent years introduced tariffs with penalties for high return temperatures and benefits for low return temperatures. This paper describes the case of a housing community of 17 buildings in their attempts to adjust to such tariffs as an integrated part of connecting to district heating. Replacing domestic hot water tanks with instantaneous heat exchangers and introducing smart meters resulted in abilities to lower the return temperature from around 40 °C to around 30 °C. However, the current design of the motivation tariffs does not yet fully compensate the consumers because the supply company provides unnecessarily high supply temperatures. Based on such efforts, this paper discusses the fairness and effectiveness of the tariffs and provides recommendations for improving them.

The purpose of this study was to evaluate the accuracy of bone-level assessments using either cone-beam computed tomography (CBCT), intra-oral peri-apical (PA) radiographs or histology following reconstructive treatment of experimental peri-implantitis.Six Labrador dogs were used. Experimental peri-implantitis was induced 3 months after implant placement. Surgical treatment of peri-implantitis was performed and peri-implant defects were allocated to one of four treatment categories; no augmentation, bone graft materials with or without a barrier membrane. Six months later, intra-oral PA radiographs and block biopsies from all implants sites were obtained. Marginal bone levels (MBLs) were measured using PA radiographs, CBCT and histology.Significant correlations of MBL assessments were observed between the three methods. The measurements in PA radiographs consistently resulted in an overestimation of the bone level of about 0.3-0.4 mm. The agreement between the methods was not influenced by the use of bone substitute materials in the management of the osseous defects.Although MBL assessments obtained from PA radiographs showed an overestimation compared to MBL assessments on corresponding CBCT images and histological sections, PA radiographs can be considered a reliable technique for peri-implant bone-level evaluations following reconstructive surgical therapy of experimental peri-implantitis.

Angewandte Chemie / International edition 61(22), e202116517 (2022). doi:10.1002/anie.202116517, Alkali metal promoters have been widely employed for preparation of heterogeneous catalysts used in many industrially important reactions. However, the fundamentals of their effects are usually difficult to access. Herein, we unravel mechanistic and kinetic aspects of the role of alkali metals in CO$_2$ hydrogenation over Fe-based catalysts through the state-of-the-art characterization techniques, spatially resolved steady-state and transient kinetic analyses. The promoters affect electronic properties of iron in iron carbides. These carbide characteristics determine catalyst ability to activate H$_2$ , CO and CO$_2$. The Allen scale electronegativity of alkali metal promoter was successfully correlated with the rates of CO$_2$ hydrogenation to higher hydrocarbons and CH$_4$ as well as with the rate constants of individual steps of CO or CO$_2$ activation . The derived knowledge can be valuable for designing and preparation of catalysts applied in other reactions where such promoters are also used., Published by Wiley-VCH, Weinheim

Chromium poisoning of the air electrode is a primary degradation mechanism for solid oxide cells (SOCs) operating under fuel cell mode. Recent experimental findings show that reversed pulse operation for SOCs operated as electrolyser cells can reverse this degradation and extend the lifetime. Here, we use a multiphysics model of an SOC to investigate the effects of reversed pulse operation for alleviating chromium poisoning of the air electrode. We study the effects of time fraction of the operation under fuel cell and electrolysis modes, cyclic operation starting after a certain duration, and fuel cell and electrolysis current densities on the cell lifetime, total power, and hydrogen production. Our modeling shows that reversed pulse operation enhances cell lifetime and total power for all different cases considered in this study. Moreover, results suggest that the cell lifetime, total power, and hydrogen production can be increased by reversed pulse operation at longer operation times under electrolysis mode, cyclic operation starting from the beginning, and lower electrolysis current densities. All in all, this paper documents and establishes a computational framework that can serve as a platform to assess and quantify the increased profitability of SOCs operating under a co-production operation through reversed pulse operation.

The ongoing green energy transition is increasing the need for dynamic and efficient Power-to-X (PtX) systems to convert surplus wind and solar power to high-value products. The solid oxide electrolysis cell (SOEC) technology offers the highest energy conversion efficiency. However, high degradation and thermal variations that cause thermomechanical stress hinders up-scaling of the SOEC technology. Here we present a novel operation method that alleviates temperature variations and minimize degradation caused by impurities and nickel migration. By rapidly switching between electrolysis mode and brief periods in fuel cell mode, a flat thermal profile is obtained. Our results thus establish a new, simple way to achieve increased SOEC stack and module size and extended lifetime. The new operation method enables dynamic operation of large SOEC modules for renewable energy powered PtX systems which could drastically decrease costs associated with production of high-value green fuels and chemicals from wind and solar power.

The transport sector contributes to approximately one third of Danish greenhouse gas (GHG) emissions and almost half of emissions from the energy sector. A unified Danish parliament agreed to reduce total emissions with 70% compared to 1990 levels by 2030. This paper estimates the potential for reducing the national transport sector GHG emissions in 2030 and proposes a pathway towards full decarbonisation in 2045 using a complex set of measures.Towards 2030, the major focus is on an extensive electrification for passenger cars, alongside the implementation of significant measures to achieve lower growth rates for kilometers travelled by car and aircraft. From 2030 onwards, a decisive focus is set on sector integration. Production of electrofuels proves to be a key measure to decarbonize aviation, shipping and long-distance road freight transport.The results show a reduction of GHG emissions of 41% in 2030 and full decarbonisation in 2045. The reduction is achieved without a significant increase of socio-economic costs. From 2030 to 2045, a substantial electrification of road transport and a focus of moving the need for mobility from roads towards rail and bicycles drives the full-decarbonisation together with the replacement of fossil fuels with electrofuels for aviation, shipping and heavy-duty road transport.

High temperature thermal energy storage units can provide the flexibility required, by storing the excess energy in the form of heat and suppling it back either into the electric grid or as heat to any energy intense industrial process. DTU Energy has constructed a vertical flow high temperature thermal energy storage unit, which uses air as a heat transfer fluid and Swedish diabase rocks as a storage medium. This storage unit can store heat at a temperature of up to 675℃ and has a thermal capacity of 1 MWhth. The main objective of this study is to present an experimentally validated 2D time dependent computational fluid dynamics model of the rock-bed thermal energy storage developed in COMSOL Multiphysics. The results show good agreement between experimental and model data. Moreover, the overall efficiency is increased when subjected to consecutive cycling.

Energy system models (ESMs) are essential for planning the energy transition and understanding its impacts. However, this transition is inherently complex and cannot always be understood by using just one model. Consequently, efforts linking different model classes are common practice to get insights into the energy system and the different dimensions around it. While existing literature has focused on proposing how such multi-model analyses could be structured, presenting applied cases, or looking into how specific aspects of other knowledge domains are included in energy modelling, a high-level overview of the practice of model coupling with ESMs is lacking. This article puts this practice into perspective by providing an outlook on two aspects: coupling ESM paradigms and model coupling with other knowledge dimensions. Coupling ESMs paradigms have often been used to expand modelling resolution, yet further emphasis should be placed on illustrating contrasting near-optimal system designs and expanding the solution space beyond optimality criteria. Model coupling across knowledge domains is desirable when providing meaningful insights about specific themes, yet, increased complexity of data, multi-model frameworks, and coordination across practices would make an all-encompassing model impractical and calls for purpose-driven model coupling to answer specific questions about the energy transition.

The transportation sector is currently undergoing a technology shift from internal combustion engines to electric motors powered by batteries. However, their limited range and long charging times limit wide-spread adoption. Electrified transportation powered by solid oxide fuel cells (SOFCs) offer an attractive alternative especially for heavy freight and long-range transportation, as this technology can provide high-efficiency and flexible fuel choices. Thus far, the technology is mostly used for stationary applications owing to the high operating temperature, low volumetric and gravimetric power density, and poor robustness towards thermal cycling and mechanical vibrations of conventional ceramic-based cells. Here, we present a novel metal-based monolithic fuel cell design to overcome these issues. Highly cost-competitive and scalable manufacturing methods are employed for fabrication, and only a single heat treatment is required, as opposed to two or three for conventional SOFCs. The design is further optimised through three-dimensional multiphysics modelling, nanoparticle infiltration, and corrosion-mitigating treatments. The monolithic fuel cell shows exceptionally high power density (5.6 kW/L) and excellent thermal cycling robustness, revealing the vast potential of SOFC technology for transport applications.

Alkali metal promoters have been widely employed for preparation of heterogeneous catalysts used in many industrially important reactions. However, the fundamentals of their effects are usually difficult to access. Herein, we unravel mechanistic and kinetic aspects of the role of alkali metals in CO

The electrification of transportation is currently seen as one of the key strategies in the sustainable energy transition. This work aims to identify the role of the electrification of transportation from a perspective of the mid-to-long term. The main focus is on the coupling of the deployment of electric vehicles (EV) and power system decarbonization. The paper combines a detailed bottom-up model for the road transportation sector, which features a detailed classification of vehicle types, with the EnergyPLAN tool, a cross-sector and cross-region energy system model of future scenarios consisting of different planning strategies and vehicle charging modes. A case study of the Beijing-Tianjin-Hebei region shows that without increasing renewable power capacity, a 100 % EV penetration can create energy savings and reduce carbon dioxide emissions by a minimum of 11 % in 2050. Moreover, considering the foreseeable technological progress in the battery, a 25 % reduction in the EV initial investment is feasible in all the investigated future scenarios.

Trigeneration compressed air energy storage (TCAES) is one of the emerging solutions that will most likely find its market as a popular energy storage technology for sector coupling. The combination of a TCAES with an organic Rankine cycle (ORC) for waste heat recovery has also been found much effective for enhanced round trip efficiency and is thus to be preferred over conventional TCAES designs. The combined configuration is claimed to offer a very high coefficient of performance (COP) exceeding 1.5. This work aims to quantify realistic performance expectations from a combined TCAES-ORC subject to real operating conditions accompanied for instance by a wind turbine. The system is dynamically modeled, and its performance is analyzed regarding energetic/exergetic efficiency, environment, and economy. To make the investigations close to real-life conditions, a medium-sized 5 MW capacity TCAES-ORC unit is considered integrated with a wind farm for off-peak electricity utilization for storage and tri-generation of heat, cooling, and electricity when charging or discharging. The location of the use case is considered West Denmark, for which wind power production and pricing profiles are available. The results show that there is a considerable collapse in the cooling and power production when the system comes to low operating loads, while heat production potential is not significantly affected. The COP factor decreases from 1.5 in nominal mode to 1.26 in the off-design mode for a sample dynamic load, where the exergetic efficiency is reduced from 64% to 58%. With such a technical operation degradation, the levelized cost of storage (LCOS) is weakened from 141 €/MWh to 153.7 €/MWh, and the potential emission reduction will fall from 4163 to 3640 tonnes of equivalent CO2 per year.

Severe degradation of Ni-YSZ (yttria stabilized zirconia) electrodes of solid oxide cells (SOCs) due to Ni migration is well known, but the literature contains apparent contradictions. The mechanisms are still under debate. Fine structured Ni-YSZ composite electrodes often degrade at operation temperature (700–950°C), because Ni particles lose electrical contact with each other as larger Ni-particles grow on the expense of smaller ones. Another type of Ni migration, which may be very damaging, is the relocation of Ni in the most active part of the Ni-YSZ cermet electrode next to the dense YSZ electrolyte. Emphasis is put on the migration of Ni away from the YSZ electrolyte in solid oxide electrolysis cells (SOECs). This is seen as an important obstacle to the commercialization of SOC systems. Apart from temperature, degradation of Ni-YSZ electrodes in SOCs is related to Ni-YSZ electrode overpotential and the local redox potential of the gas mixture inside the porous Ni-YSZ electrode. A unifying Ni migration mechanism is proposed, and methods of alleviating the electrode degradation are discussed. The hypothesis is that Ni migrates via surface diffusion of Ni(OH)x species below ca. 800°C and via Ni(OH)x species in gas phase above ca. 900°C.

Objective: To compare retinal function assessed by full-field electroretinography (ffERG) and multifocal electroretinography (mfERG) in diabetes without retinopathy, diabetes with moderate non-proliferative diabetic retinopathy (NPDR) and in the absence of diabetes. Methods: Scotopic and photopic ffERG and mfERG was made in non-fasting volunteers, including 26 diabetic participants without retinopathy, 22 diabetic participants with moderate NPDR and 22 participants without diabetes using full International Society for Clinical Electrophysiology of Vision protocols. Results: Of the ffERG responses, significant deviation (p ≤ 0.05, corrected for multiple sampling and other relevant confounders) from the non-diabetic participants was seen in the diabetic participants only for the OP1-OP3 oscillatory amplitudes and the OP2 implicit time. This finding was independent of whether retinopathy was present or not. For the mfERG, minor amplitude or implicit time deviations were found for a small number of rings (R2, R4 and R5). Receiver of operating characteristic analysis showed that the single most prominent abnormality of the ffERG in diabetes, regardless of whether retinopathy was present or not, was the OP2 implicit time (area under the curve ≥ 0.80). Conclusion: This bi-modal study of electroretinographic characteristics found that the most prominent anomaly associated with diabetes was a prolongation of the implicit time of the OP2 of the scotopic ffERG, while the most prominent added effect of non-proliferative diabetic retinopathy was a further prolongation of the OP2 implicit time. Although the variation in ERG characteristics is far too large for diagnostic purposes, the close association of the oscillatory potentials with the amacrine cells of the retina indicate that their function is particularly sensitive to diabetes.

Energy modeling and planning problems associated with technical, economic, political, and social development have been critical concerns in energy system planning and greenhouse gas emission control for both national and worldwide for many years. This paper modeled and analyzed the current and future energy supply and demand for an oil-rich energy system because energy intensity is very high in such countries. A high shared fossil fuels energy system is modeled, and an appropriate energy mix is proposed to meet the national commitment in Paris Agreement. The EnergyPLAN is used to model the energy system. Hourly actual energy demand and supply are provided for 2004–2016 for all energy sectors and subsectors and anticipated 2030. Five different scenarios are analyzed, and results show that the power sector is more influential than other energy demand sectors. Efficiency improvement of the thermal power plans and the integration of renewable energy resources into the power sector are more useful for reducing Total Primary Energy Consumption, CO2, and variable cost than other scenarios. In the proper scenario, a 1% improvement in the thermal power plants efficiency and 22% annual average growth rate in renewable energy capacity, 4% CO2 reduction can be achieved. It is concluded that in oil-rich counties such as Iran, the energy system efficiency improvement, particularly in electricity production, is more useful for the overall CO2 reduction goals. Efforts for total CO2 reduction benefit the national energy system economy, and the international community will benefit from a more efficient energy system. We believe that by total primary energy supply reduction in oil-rich countries, the international market's energy supply will be increased, which further reduces the pressure on the global oil and gas prices.

A critical factor for improving the long-term stability/reliability of solid oxide cell stacks is ensuring good adhesion between the stack components. Specifically, ensuring strong adherence between the oxygen electrode and the interconnect is challenging. This work compares the suitability of several materials as contact layers between a La0.6Sr0.4CoO3–δ-Ce0.8Gd0.2O2 composite oxygen electrode and Mn1.5Co1.5O4 or Co coated metallic interconnects. The contact materials were screened based on measurements of the interface fracture energy using four-point bending of sandwiched samples. The highest fracture energies were measured using a CuMn metallic, spinel forming foam as the contact layer. The fracture energy of the interface between a Mn1.5Co1.5O4 coated interconnect and the contact layer is ~8 times higher using the CuMn foam compared to using the conventional perovskite oxides (La0.8Sr0.2)0.98MnO3-δ, La0.6Sr0.4CoO3–δ, (La0.8Sr0.2)0.98MnO3-δ + La0.6Sr0.4CoO3–δ or LaNi0.6Fe0.4O3 as the contact material. The interface bonding and fracture mechanisms are discussed on the basis of scanning electron microscopy investigations.

Non-oxidative dehydrogenation of propane is one of the most promising technologies for propene production in terms of environmental impact and sustainability. The purpose of the present study was to develop environmentally friendly and low-cost alternatives to currently applied Pt- or CrOx-based catalysts. Rutile TiO2-based catalysts with supported ZnOx and ZrOx species were established to show promising performance under industrially relevant conditions. The amount of propene produced within 3 h on propane stream at 550 °C over the optimized catalyst with 2 wt% Zn and 5.6 wt% Zr is close to that obtained over commercial-like K–CrOx/Al2O3 and the state-of-the-art Cu/YZrOx catalyst. The selectivity to propene over our catalyst was about 95% at a propane conversion of about 23%. The kind of active sites and the effect of ZrO2 addition on catalyst performance and physicochemical properties were elucidated owing to the application of complementary characterisation techniques such as XRD, N2 physisorption, HRTEM, EDX, XPS, X-ray absorption spectroscopy, NH3-TPD, CO-TPR, Raman and O2-TPO. ZnOx clusters with 1–3 Zn atoms were concluded to be the active sites. ZrO2 enhances their intrinsic activity and inhibits the formation of the inactive rhombohedral ZnTiO3 phase.

This paper demonstrates the potential of Eu2O3 and Gd2O3 as catalysts for non-oxidative propane dehydrogenation to propene. They reveal a higher activity than the state-of-the-art bare ZrO2-based catalysts due to the higher intrinsic activity of Gdcus or Eucus in comparison with that of Zrcus (cus = coordinatively unsaturated).

A convenient methodology for perfluoroalkylation including trifluoromethylation of (hetero)arenes with perfluoroalkyl bromides was developed. Key for the success is the use of a specific cobalt-based nanocatalyst, which can be recycled at least up to 4 times. The scope of this first cobalt-catalyzed perfluoroalkylation is presented and detailed catalyst characterization (e.g. analytical STEM, XPS, and XRD) has been carried out.

In this work, steady-state tests of propane dehydrogenation, density functional theory calculations, operando UV–vis spectroscopy, ex situ and in situ electron paramagnetic resonance spectroscopy, ...

A major challenge in mixed fisheries is achieving acceptable size selectivity for morphologically different species using the same fishing gear. Separator trawls can have different selective properties in the upper and lower compartments and provide successful separation of species. We used a horizontally divided codend with small square meshes (40 mm) and a simple frame to stimulate fish to swim into the upper compartment. The majority of the fish were separated successfully from Nephrops (Nephrops norvegicus), but their preference were uniform. Less than 10% of the Nephrops entered the upper compartment. Length-based analysis revealed three patterns of separation efficiency among nine commercial species: length-dependent separation and preference for the upper or lower compartments. The separation efficiency should be improved for small roundfish and flatfish. There was little diel effect on the separation efficiency. The preference of fish for a compartment, taking the relative height of that compartment into account, was established for this and similar previous studies to enable comparison of results. We recommend length-based analysis to account for the fished population when interpreting results.

C–O and C–N cleavage reactions play a fundamental role in synthetic chemistry and biomass valorization. Many efforts have been done in the past in order to develop efficient catalysts able to mediate these transformations. However, still some drawbacks are present: necessity for additives and occurrence of side reactions. Here, an array of Ni-based catalysts derived from the thermal decomposition of a Ni(II)/phenanthroline complex onto different supports was prepared. Ni–N–C@Al2O3-1000 material (pyrolyzed at 1000 °C) was the most efficient catalyst for both O- and N-debenzylation of various substrates (>20 examples) using dihydrogen as reductant. Advantageously, this process is water tolerant, proceeds free of any additive, and does not show overhydrogenation of the arene ring. The structure, morphology, and chemical composition of Ni–N–C@Al2O3-1000 have been elucidated. It is constituted by variously sized Al2O3-supported Ni(0)/NiOx nanoparticles (NPs) embedded by layers of nitrogen-doped carbon.

This review gives first a brief view of the potential availability of sustainable energy. It is clear that over 100 times more solar photovoltaic energy than necessary is readily accessible and that practically available wind alone may deliver sufficient energy supply to the world. Due to the intermittency of these sources, effective and inexpensive energy-conversion and storage technology is needed. Motivation for the possible electrolysis application of reversible solid-oxide cells (RSOCs), including a comparison of power-to-fuel/fuel-to-power to other energy-conversion and storage technologies is presented. RSOC electrochemistry and chemistry of H2O, CO2, H2, CO, CnHm (hydrocarbons) and NH3, including thermodynamics and cell performance, are described. The mechanical strength of popular cell supports is outlined, and newly found stronger materials are mentioned. Common cell-degradation mechanisms, including the effect of common impurities in gases and materials (such as S and Si), plus the deleterious effects of carbon deposition in the fuel electrode are described followed by explanations of how to avoid or ease the consequences. Visions of how RSOCs powered by sustainable energy may be applied on a large scale for the transportation sector via power-to-fuel technology and for integration with the electrical grid together with seasonal storage are presented. Finally, a brief comparison of RSOCs to other electrolysis cells and an outlook with examples of actions necessary to commercialize RSOC applications are sketched.

Methane dry reforming (DRM) was studied over Ni catalysts with low active metal content (2.5 wt%) supported on MgO-Al2O3. The aim was to develop catalysts that are stable against different deactivation effects and achieve outstanding DRM reactivity at severe conditions. The solids were characterized using N2 physisorption, X-ray diffraction, temperature-programmed reduction, UV–vis diffuse reflectance spectroscopy, and scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy. The results show that the low Ni content catalysts may not only suffer from rapid carbon deposition and particle growth but also Ni re-oxidation. La addition and citric acid complexation during the Ni catalyst preparation not only stabilizes Ni dispersion but also limits the Ni re-oxidation as well as the coking rate during the reaction. The most effective Ni catalyst shows high and stable DRM reactivity over 160 h with an exceptionally high productivity of syngas. Furthermore, catalysts of such type were evaluated in DRM with CH4-rich feed to mimic the direct conversion of some biogases or specific natural gases. Even at such harsh conditions the spent catalysts exposed remarkably low carbon deposition. Those results are promising for Ni catalyst development for industrial scale DRM.

In electrochemical devices such as solid oxide cell stacks, many physical phenomena are interacting on many different length scales in an intricate geometry. Modeling is a strong tool to understand the interior of such devices during operation, enhance their design and investigate long-term response (degradation). Computations can however be challenging as the many geometric details and coupled physical phenomena require a significant computational power, and in some cases, even state-of-the-art clusters will not be sufficient. This hinders the use of the models for the further development of the technology. In this work, we present an original type of solid oxide cell stack model, which is highly computationally efficient, resulting in computations which are two orders of magnitude faster than the conventional type of stack models with all geometric details explicitly represented. In the model presented here, the geometric details are implicitly represented by using the so-called homogenization. The resulting homogeneous anisotropic media provides the correct overall response (temperature, species, molar fractions, etc.). Local details as the mechanical stress in the electrolyte are not represented explicitly. These can be retrieved by localization through sub-models (multiscale model), in some cases without loss of computational efficiency, as demonstrated.

Degradation of nickel-stabilized zirconia (Ni-SZ) electrodes is predominantly due to four features 1) high mobility of Ni, 2) fragile nature of SZ ceramics, 3) narrow three phase boundary (3PB), and 4) effects of impurities: i) in blocking (poisoning of 3PB), and ii) on mobility of Ni. Impurities may be contaminants in reactant gases and influenced by the reactants H2O, CO2 and CO, or impurities in cell and stack materials. Examples of important degradation types and hypotheses of the degradation mechanisms are described. Examples are: a) loss of electrochemical contact between Ni and YSZ (yttria stabilized zirconia) particles and loss of contact between Ni-Ni particles followed by Ni-migration away from the YSZ electrolyte - one reason is hypothesized being a result of huge potential and thermal gradients at the 3PB; b) growth of Ni-particles; c) redoxing; d) blocking of 3PB and reaction sites by impurities like Si and S. Mitigation methods are discussed.

Solid oxide fuel cells and electrolysis (SOFC, SOE = SOC) are efficient technologies to link together energy sectors such as power, gas, and heat. They can thus emerge as key technologies in the current energy transitions towards systems based on renewable energy sources. DTU Energy has a long history of research in the areas of SOC and has currently an effort of ca. 35 person-years per year. The presentation will introduce the recent achievements ranging from materials development, cell & stack development, and advanced diagnostics to system analysis and modelling. Examples are significantly improved cells based on state-of-the-art, metal supported cell types, use of alternative fuels such as ammonia and biogas, stack and stack component development, and increased basic understanding aided by phase-field and multi-physics modelling.