FeOx Species Research Articles

Catalytic Fe2+ Cation Pair Site for Base-free N-Alkylation of Aromatic Amines with Alcohols.

The development of heterogeneous Fe catalysts is very attractive due to the ubiquitous, abundant, and inexpensive nature of Fe as a resource. However, Fe oxides are commonly inert as catalysts and hence, the design and fabrication of active Fe sites are essential. Herein, the fabrication of an active Fe cation pair site by simple reduction treatment of SiO2-supported FeOx (FeOx/SiO2) is presented. The active Fe cation pair site was formed by the removal of the oxygen atom between Fe cations of the FeOx on SiO2, namely oxygen vacancy formation, which is induced by temperature-controlled reduction treatment. 773 K reduction maximized the Fe cation pair sites without the decomposition of FeOx species, which was an effective catalytic one for the N-alkylation of amines mainly proceeded through Meerwein-Ponndorf-Verley (MPV) type reduction, which is achieved by the stabilization of six-membered ring transition state derived from imines and alcohols over the open active site of the Fe cation pair site.

One‐Pot Cascade Reaction from Epoxide to Carboxylic Acids Using Bifunctional Fe‐ZSM‐5

AbstractThe quest for sustainable synthesis of carboxylic acids has led to the exploration of innovative routes and catalysts for the oxidative cleavage of carbon−carbon double bonds, prevalent in bio‐derived molecules. This process involves multiple steps including epoxidation, hydrolysis and vicinal diol cleavage, often catalysed by unsustainable homogeneous or noble‐metal catalysts. In this study, we present the utilization of Fe‐ZSM‐5 as a versatile bifunctional catalyst capable of catalysing both hydrolysis and vicinal diol cleavage steps, utilizing propylene oxide as model compound and H2O2 as oxidizing agent. The prepared Fe‐ZSM‐5 features the zeolite intrinsic Lewis and Brønsted acidity functions, essential for the hydrolysis step, as well as high fractions of monomeric FeOx species, crucial for the subsequent vicinal diol cleavage, leading to streamlined carboxylic acids formation in a one‐pot, two‐step process. Moreover, by combining Fe‐ZSM‐5 with TS‐1, renowned for its epoxidation activity, we demonstrate the complete cascade reaction in one pot, under mild conditions, starting from ethylene. Our study expands the utility of cost‐effective zeolite‐based catalysts enriched with abundant Fe metal for the one‐pot oxidative cleavage of C=C double bonds, offering a promising pathway towards sustainable carboxylic acid synthesis.

Study on the reducible metal oxide carriers to regulate the catalytic reaction performance of CO2 with ethane

Aiming at the resource utilization of CO2 and the value-added catalytic conversion of ethane, different reducibility oxide carriers were used to study. Through catalytic reaction experiments, catalyst characterization and kinetic analysis, the interaction between reducible carriers and active metals and their regulation on the catalytic reaction performance of ethane with CO2 were revealed. Fe1.5Ni0.5/CeO2 has the highest ethylene selectivity of 87% near 650 °C, and is a good catalyst for the CO2-assisted ethane oxidative dehydrogenation to ethylene reaction. The strong interaction between the reducible CeO2 and ZrO2 carriers and active metals makes the Fe–O–Ce and Fe–O–Zr covalent bonds on the Fe1.5Ni0.5/CeO2 and Fe1.5Ni0.5/ZrO2 catalysts stronger than Fe–O–Ti and Fe–O–Al covalent bonds on Fe1.5Ni0.5/TiO2 and Fe1.5Ni0.5/γ-Al2O3 catalysts. The lattice oxygen on the reducible catalyst is more readily involved in the reaction. The strong interaction between the active metal and the carrier results in the reduction of the FeOx species and the formation of new active sites, resulting in a high reactivity of the catalyst. The mutually promoted redox cycle between the active species Fe3+/2+-Ni2+/0 and the reducible carrier variable metal Ce4+/3+ species improves the catalytic performance for the reaction of ethane awith CO2.

Insight into the Alkali Resistance Mechanism of FeMoTiOx Catalysts for NH3 Selective Catalytic Reduction of NO: Self-Defense Effects of MoOx for Alkali Capture.

The deactivation of selective catalytic reduction (SCR) catalysts caused by alkali metal poisoning remains an insurmountable challenge. In this study, we examined the impact of Na poisoning on the performance of Fe and Mo co-doped TiO2 (FeaMobTiOx) catalysts in the SCR reaction and revealed the related alkali resistance mechanism. On the obtained Fe1Mo2.6TiOx catalyst, the synergistic catalytic effect of uniformly dispersed FeOx and MoOx species leads to remarkable catalytic activity, with over 90% NO conversion achieved in a wide temperature range of 210-410 °C. During the Na poisoning process, Na ions predominantly adsorb on the MoOx species, which exhibit stronger alkali resistance, effectively safeguarding the FeOx species. This preferential adsorption minimizes the negative effect of Na poisoning on Fe1Mo2.6TiOx. Moreover, Na poisoning has little influence on the Eley-Rideal reaction pathway involving adsorbed NHx reacting with gaseous NOx. After Na poisoning, the Lewis acid sites were deteriorated, while the abundant Brønsted acid sites ensured sufficient NHx adsorption. As a benefit from the self-defense effects of active MoOx species for alkali capture, FeaMobTiOx exhibits exceptional alkali resistance in the SCR reaction. This research provides valuable insights for the design of highly efficient and alkali-resistant SCR catalysts.

Highly stable FeNiMnCaO catalyst for integrated CO2 capture and hydrogenation to CO

The integrated CO2 capture from flue gas and hydrogenation can be realized by the consecutive calcium-looping (CaL) and reverse-water–gas-shift (RWGS) reactions. However, the incompatibility between the catalysis and adsorption components aggravates the sintering and deactivation of metal particles and CaO base material during the high-temperature process. Herein, we prepared a highly efficient and stable FeNiMnCaO material via a modified sol–gel method for in situ CaL and RWGS reaction, exhibiting a CO2 adsorption capacity of 13.2 mmol g−1 at 40 cycles with 58.0 % CO2 conversion and 100 % CO selectivity at 700 °C. The highly-dispersed Fe and Ni species in the developed catalyst not only suppressed the sintering of MnCaO, but also synergistically benefited the RWGS reaction, where FeOx species promoted CO2 adsorption and metallic Ni facilitated H2 dissociation. The reaction followed the H-assisted association formate mechanism, in which adsorption of CO2 occurred at the FeOx-CaO interface with the aid of the hydroxyl surface groups to form bidentate bicarbonates, followed by dehydration to bidentate formate and decomposition to CO and H2O in the presence of Ni-dissociated reactive H* species.

Enhanced ruthenium selectivity for the conversion of FAMEs to diesel-range alkanes by surface decoration of FeOx species

Ruthenium-based catalysts have been widely used in the lignin depolymerization and polystyrene hydrogenolysis reactions due to its superior hydrogenolysis activity for C-O and C-C bonds. However, serious cleavage of C-C bonds at high temperatures greatly limits its application in the production of green biodiesel from the conversion of natural oils and bio-derived fatty esters. In this work, we found that introducing a suitable second less-reactive metal (e.g., Fe, Zn) can effectively suppress the hydrogenolysis activity of ruthenium (Ru) metal for C-C bonds and exhibit a high selectivity (>90 %) to diesel-range alkanes (C15-C18 alkanes) in the conversion of fatty acid methyl esters (FAMEs) even at high reaction temperature (250 °C) over the Ru1Fe0.5 catalyst, while an obvious cracking reaction was observed from 210 °C over the monometallic Ru catalyst. Detailed characterization and theoretical calculation results reveal that the introduction of Fe species in the RuFe catalysts weakens the interaction between catalyst and the resulting alkanes, which inhibits the cracking of alkanes. Specifically, adding Fe species breaks the ensemble of Ru atoms and decreases the binding affinity of metallic Ru for H2, which suppresses the activity of Ru metal for the hydrogenolysis of C-C bonds and exhibits a high selectivity to diesel-range alkanes. This research provides valuable information for improving the hydrodeoxygenation (HDO) selectivity of Ru-based catalysts while inhibiting its high hydrogenolysis activity for C-C bonds.

Amorphous FeOx–Mn0.1Oy catalyst with rich oxygen vacancies for ammonia selective catalytic reduction of nitrogen oxide at low temperatures

Amorphous materials have garnered extensive research interest in heterogeneous catalysis because of their high surface area and interconnected micro/mesopores. In this study, an amorphous metal oxides (FeOx-Mn0.1Oy) with large surface areas, sufficient oxygen vacancies, excellent redox properties is prepared for the ammonia selective catalytic reduction (NH3-SCR) of NOx. Benefits from the large surface area, this catalyst possess higher adsorption and activation ability for O2 and NO which further enhanced the catalytic activity at low temperatures (90–240 °C). The incorporation of Mn into FeOx species inhibits the crystallization of hematite, further resulting in an increase of the surface area and surface acid sites in the as-prepared catalyst. Furthermore, the number of oxygen vacancies increases by the incorporation of manganese, which reduces the apparent activation energy of hematite and enhances the redox property of the amorphous FeOx–MnOy catalyst. The reaction mechanism of this catalyst also has been proposed based on the result of in situ DRIFTs experiment results.

Fabrication of highly oxidized Pt single-atom catalysts to suppress the deep hydrogenation of unsaturated aldehydes

In this work, we first reported the fabrication of single-atom Pt catalysts with high oxidation state through a mild hydrolysis method using platinum acetylacetonate as the precursor and SBA-15 coated with functional FeOx nanoclusters as support, and evaluate their catalytic performance towards unsaturated aldehydes hydrogenation. Pt1-FeOx/SBA-15 featuring the high coordination number of Pt-O exhibited markedly high selectivity for hydrogenation of CO group (> 95 %) when cinnamaldehyde conversion is 100 %, and further hydrogenation of target product could be efficiently inhibited over a prolonged period of time, and the universality of chemoselectivity was also evidenced in other unsaturated aldehydes. The experimental results and theoretical calculations revealed that the synergism of highly electron-deficient Pt single-atoms and FeOx species is responsible for the selectivity control and the inhibition of further hydrogenation. The developed strategy offers a facile approach to the rational design of high-efficient single-atom catalysts for the selective hydrogenation with multiple intermediates.

Defect‐Decorated NiFe Bimetallic Nanocatalysts for the Enhanced Hydrodeoxygenation of Guaiacol

AbstractSeries of Ni‐based nanocatalysts were fabricated for the HDO of lignin‐derived guaiacol to cyclohexane via a single‐source Ni−Fe−Al layered double hydroxide precursor route and characterized by XRD, BET, TEM, XAS, XPS, H2‐TPR, H2‐TPD, NH3‐TPD, and pyridine absorbed in situ FT‐IR. As‐fabricated bimetallic NiFe nanocatalyst bearing a Fe/Ni molar ratio of 0.5 : 3 attained a higher cyclohexane yield of 70.5 % under mild reaction conditions (i. e., 230 °C and 1.0 MPa of initial hydrogen pressure), compared to monometallic Ni and other NiFe bimetallic nanocatalysts, as well as monometallic Ni and bimetallic NiFe catalysts prepared by the impregnation method. Combination of experimental results and density functional theory calculations manifested that interfacial FeOx species profoundly facilitated the demethoxylation processes of guaiacol and 2‐methoxycyclohexanol intermediate, while both bimetallic NiFe sites and interfacial FeOx species greatly promoted the dehydroxylation of cyclohexanol intermediate.

Rationally control the path of hydrodeoxygenation of palmitic acid over Ni/red-mud catalysts by surface decoration of oxophilic MoOx species

Red mud supported Ni (Ni/RM) catalysts have been explored to the hydrodeoxygenation (HDO) of palmitic acid, however, the decarbonylation (DCO)/decarboxylation (DCO2) is dominant. Therefore, the modification the oxophilic nature of catalysts can significantly impact their path of HDO and selectivity to aim products. Herein, MoOx-decorated Ni-Mo/RM catalysts with a hierarchical flower-like micro/nanostructure were prepared and applied in the HDO of palmitic acid. The effect of MoOx addition was investigated to control the path of HDO, resulting in the changing of carbon number distribution of the product. Combined with several comprehensive structural characterizations and catalytic HDO test, it is shown that the surface defective MoOx species and FeOx species near the metallic sites could significantly facilitate the C-O bond weakening, generated more direct deoxygenation product (hexadecane). Whereas the excessive Mo loading leads to clear altering of surface chemistry (i.e., decrease of specific surface area, pore volume and Mo0 species, increase of reduction temperature and CO2 adsorption, uneven dispersion, and agglomeration of Ni species), resulting in the decrease of palmitic acid conversion. As the main oxide in RM, Fe2O3, Al2O3 and SiO2 were used as supports to load Ni-Mo bimetals respectively to explore the contribution of different components in RM to the distribution of hydrodeoxygenation products of palmitic acid.

Study on the promotion of FeOx species on water-gas shift reaction in methanol aqueous phase reforming over PtFe/Al2O3 catalyst

Hydrogen production by catalytic aqueous phase reforming (APR) of biomass-derived oxygenates is a promising route to produce hydrogen in a renewable way. As the typical APR catalyst, Pt/Al2O3 is confronted with high methanation activity that consumes H2 and produces undesired CH4 during the treatment of methanol solution. In contrast, WGS reaction is the main pathway to boost H2 generation during APR process. In this work, a series of PtFe/Al2O3 catalyst with different Fe contents were prepared, characterized and tested for the methanol APR reaction. XRD, TEM, XPS and H2-TPR technologies were applied to study the change of physicochemical properties with the addition of iron. The restriction on methanation and promotion on WGS reaction were proved as well. With the increase of Fe content, the interaction between Pt and FeOx species have both positive and negative effects on APR reactivity while the CH4 selectivity descending continuously from 9.25% to as low as 0.60%. Besides, the effects of reduction temperatures (250–350 °C) of Pt0.5Fe/Al2O3 catalyst on APR performances were also investigated. An “Oxygen dynamic transfer cycle” between H2O/CO∗ and FeOx species with oxygen vacancies is proposed and verified. This indirect WGS reaction through lattice oxygen on FeOx species that boosting WGS reactivity helps improving H2 selectivity in the gas products of methanol APR.

Low‐Coordinated Iron(II) Siloxide Complexes – Structural Diversity and Reactivity Towards O2 and Oxygen Atom Transfer Reagents

AbstractThe coordination chemistry of Fe2+ ions in combination with a monodentate siloxide ligand Ph3SiO− (L) was investigated. Using a Fe/L stoichiometry of 1 : 3 the complex [Na(DME)][FeL3], 2, with the iron center in a trigonal ligand environment was isolated and through decreasing the siloxide amount fraction 2 was shown to form via a unique example of a dinuclear complex, where one of the iron ions has a quasi‐trigonal and the other one a tetrahedral coordination sphere, namely [Na(DME)][Fe2L5], 1. If, however, 4 equivalents of L are employed, the tetrasiloxido ferrate(II) anion with a tetrahedral structure is generated, so that the product [Na(DME)]2[FeL4], 3, can be isolated. 2 reacts instantly with O‐atom transfer reagents, also at low temperatures, but no reaction intermediate could be identified. From the product mixture the iron(III) siloxide complex [Na(DME)3][FeL4], 4, could isolated by crystallization as the main product. Likewise, the reaction with dioxygen proceeded rather fast and added substrates did not intercept any intermediate upon its formation. However, in the presence of cyclohexene oxidation products were observed. They correspond to the typical radical‐chain‐derived products of cyclohexene suggesting, that initially a reactive FeOx species is generated that via an H atom abstraction from cyclohexene triggers its autoxidation.

Restructuring effects of Pt and Fe in Pt/Fe-DMSN catalysts and their enhancement of propane dehydrogenation

Propane dehydrogenation (PDH) over Pt-based catalysts has drawn particular attention as a propene on-purpose production technology. The addition of a promoter and the dispersion of Pt have significant effects on catalytic performance. Herein, Fe-doped dendritic mesoporous silica nanoparticle (Fe-DMSN) supported Pt catalysts were developed, which show high catalytic activity and selectivity for PDH. We found that the reduction process induces redispersion rather than agglomeration of Pt, which is favorable for PDH reaction. UV-Vis diffuse reflectance spectroscopy (DRS) and Raman spectra revealed that the restructuring of Fe from aggregated FeOx species to isolated Fe3+ species occurred during the loading of Pt onto the Fe-DMSN supports as a resulting of the interaction between Pt and Fe. The stable isolated Fe3+ species promotes Pt redispersion during the reduction process, which results in a strong metal (Pt)–support (Fe-DMSN) interaction. A high catalytic activity for PDH, even during a 60 h long-term test, was obtained on Pt/0.4Fe-DMSN because of the strong interaction between the isolated Fe species and Pt species.

Boosting Amination of 1‐Octanol to 1‐Octylamine via Metal‐Metal Oxide Interactions in NixFe1/Al2O3 Catalysts

AbstractThe synthesis of 1‐octylamine, a primary platform molecule, remained a great challenge in catalysis. In this work, NixFe1/Al2O3 was used for direct amination of 1‐octanol to 1‐octylamine. Catalyst evaluation indicated that the promotion effect of Fe/Ni ratio on the catalytic amination activity followed a volcano curve while the selectivity to 1‐octylamine was positively correlated with the Fe loading. Compared with the Ni/Al2O3 catalyst, the amination activity was increased by 2.8 times by optimizing the Fe/Ni ratio to 0.33, and the selectivity to 1‐octylamine was increased from 84.0 % to 96.3 % when increasing the Fe/Ni ratio from 0 to 1. Based on catalyst characterizations, the good performance of NixFe1/Al2O3 was ascribed to the combined modification effect of the NiFe alloy and Ni−FeOx interface. The FeOx species enriched on the Ni particle surface provided sufficient Fe2+/Fe3+−O2− sites for the activation of 1‐octanol, and the cooperation between Ni sites and Lewis acid‐base pairs enhanced the amination of 1‐octanol to 1‐octylamine. This work sheds new light on the design of Ni‐based catalysts without using a noble metal for primary amine preparation.

Preparation of oxygen reactivity-tuned FeOx/BN catalyst for selectively oxidative dehydrogenation of ethylbenzene to styrene

Oxidative dehydrogenation of ethylbenzene to styrene is considered to be an eco-friendly process, but suffering from overoxidation of the product to carbon oxides due to uncontrollable oxygen reactivity of the catalysts. Here, we report a boron nitride-supported FeOx (FeOx/BN) catalyst, over which an industrially acceptable styrene selectivity (94%) and productivity (0.9 gST gcat−1 h−1) at the conversion of 60% can be attained under oxygen-rich conditions. Based on the investigation of kinetics, CH3OH-TPD, H2-TPR, and O2 pulse reaction, BN support is found to mitigate the oxygen reactivity of FeOx via the strong interaction between the FeOx clusters and the BOx species stemmed from the BN support, which suppresses the overoxidation of ethylbenzene and styrene to carbon oxides. The catalytic tests and structural characterizations reveal that the redox FeOx species initiate the dehydrogenation and then quinone/carbonyl sites on the newly formed coke deposition over FeOx/BN catalyst leads to the increase of activity during the induction period. With the aid of the FeOx and BOx species, the balance between coke deposition and its gasification rates was achieved under oxygen-rich conditions, guaranteeing stable styrene selectivity and productivity.

Confinement chemistry of FeOx centers for activating molecular oxygen under ambient conditions.

Activating molecular oxygen under mild conditions is highly important for developing advanced green technologies and for understanding the origin and running of life as well, which still remains a challenge. In this work, we report on the confinement chemistry for activating molecular oxygen over oxides under mild conditions by presenting the synthesis and characterization of FeOx species confined to the pores of support CeO2 nanospheres. Active catalytic materials are obtained by a controllable three-step method via the formation of porous CeO2 nanospheres that have an average diameter of 120 nm and exhibit a large surface area of 168 m2 g-1 and a pore size of 18.7 nm, confining FeOx in intimate contact with ultra-small Pt particles in pores. The optimized PtOy-FeOx/CeO2-H catalyst showed an excellent performance in the preferential oxidation of CO reactions, as featured by 100% CO conversion at room temperature with almost no attenuation in a prolonged operation, which could not be accessible without pore-confined FeOx centers. Mechanical studies prove that the reaction progresses via abnormal non-competitive adsorption associated with synergistic roles from uniform loading, stabilization of divalent Fe species, surface oxygen activation on CeO2 supports, and the reduced H2 spillover effect on Pt0, making the CO species adsorbed on Ptδ+ easier to be desorbed. The methodology demonstrated here may inspire one to explore more advanced catalysts with high activity at room temperature essential for a wide range of applications.

Pseudocapacitive behaviour of iron oxides supported on carbon nanofibers as a composite electrode material for aqueous-based supercapacitors

Due to the pseudocapacitive charge storage, transition metal oxides occupy a prominent position as high-energy-density electrode materials for supercapacitors. Environmentally friendly, facile synthesis and earth-abundant precursor materials are highly desirable in the investigation of novel electrodes. We report the synthesis of a binder-free electrode composed of iron oxide (FeOx) nanoparticles supported on radially oriented multi-walled carbon nanofibers (CNF). Characterization studies revealed a homogeneous distribution of nanoparticles composed of α-Fe2O3 (hematite), γ-Fe2O3 (maghemite), and Fe3O4 (magnetite) phases on the CNF scaffold. A high specific pseudocapacitance of 239.2 F g−1 was verified for the iron oxides due to contributions of the reversible solid-state redox reactions involving the Fe(II)/Fe(III) redox couple. Likewise, this work also discusses in detail the charge storage mechanism involving the FeOx species. It is reported a facile synthesis of an electrode material with a pseudocapacitive behaviour, good cyclability, and low equivalent series resistance (e.g., 3.79 mΩ g). As seen, the composite electrode material is promising for the energy storage process in aqueous-based supercapacitors.

Ultraviolet/ozone treatment for boosting OER activity of MOF nanoneedle arrays

In this study, we developed a hydrothermal method to grow Fe-based MOF nanoneedle arrays on a nickel foam as well as a combined ultraviolet/ozone(UV/O3) treatment strategy to improve the OER activities of the non-precious metal–organic frameworks (MOFs) to the level even higher than that of the commercially-available precious metal catalysts (e.g., IrO2). It was found that Fe atoms existing in the Fe-MOF nanoneedles through coordination bonds were partially transformed into active FeOx species in-situ by the synergistic effect of UV and O3, because UV treatment can dissociate some coordination bonds to form free Fe ions, which are simultaneously oxidized to FeOx species by ozone. As a result, the combined UV/O3 treatment greatly reduced the resistance, increased the specific surface area and the number of active sites, and hence the increased catalytic activity and stability. Specifically, UV/O3 treated Fe-MOF nanoneedle arrays supported on nickel foam exhibited an excellent OER performance with a low overpotential (218 mV at 10 mA cm−2) and low Tafel slope (38.8 mV dec-1), outperformed the commercial IrO2 catalyst. This simple methodology developed in this study should have broad implications for the development of other new low-cost, but highly efficient, catalysts for OER and beyond.

Selective 5-Hydroxymethylfurfural Hydrogenolysis to 2,5-Dimethylfuran over Bimetallic Pt-FeOx/AC Catalysts

The selective hydrogenolysis of 5-hydroxymethylfurfural (HMF) platform molecule to 2,5-dimethylfuran (DMF) has attracted increasing attention due to its broad range of applications. However, HMF, with multiple functional groups, produces various byproducts, hindering its use on an industrial scale. Herein, a bimetallic Pt-FeOx/AC catalyst with low Pt and FeOx loadings for selective HMF hydrogenolysis to DMF was prepared by incipient wetness impregnation. The structures and properties of different catalysts were characterized by XRD, XPS, TEM, ICP-OES and Py-FTIR techniques. The addition of FeOx enhanced Pt dispersion and the Lewis acidic site density of the catalysts, and was found to be able to inhibit C=C hydrogenation, thereby im-proving DMF yield. Moreover, the presence of Pt promoted the reduction of iron oxide, creating a strong interaction between Pt and FeOx. This synergistic effect originated from the activation of the C–O bond over FeOx species followed by hydrogenolysis over the adjacent Pt, and played a critical role in hydrogenolysis of HMF to DMF, achieving a yield of 91% under optimal reaction conditions. However, the leaching of Fe species caused a metal–acid imbalance, which led to an increase in ring hydrogenation products.

Cover Feature: Spatially‐Resolved Insights Into Local Activity and Structure of Ni‐Based CO2 Methanation Catalysts in Fixed‐Bed Reactors (ChemCatChem 13/2021)

The Cover Feature illustrates the gradients in structure and activity along a catalytic fixed-bed reactor during CO2-methanation. In the focus of this study are Ni-based catalysts. In their Full Paper, by combining spatial activity profiling and complementary structural X-ray absorption spectroscopic studies, M.-A. Serrer, M. Stehle et al. uncovered relationships between the course of the reaction including gas phase concentration and the structure of the catalysts. In case of a bimetallic Ni-Fe-catalyst, a strong correlation between Fe oxidation state and the amount of water in the gas atmosphere was found. An oxidation of Fe under formation of FeOx species is able to protect the active Ni0 centers from oxidation and can offer an alternative CO2 activation pathway. Compared to a conventional Ni-based catalyst, this results in higher activity and selectivity. More information can be found in the Full Paper by M.-A. Serrer, M. Stehle et al.