The high demand for robust, cheap and efficient CO2 methanation catalysts is constantly growing as the challenges are evolving and industrial relevance is increasing. In this work, a series of nanoscale nickel-magnesium oxide (NM) catalysts derived from a coprecipitated bimetallic single source precursor was compared to a commercial Ni/Al2O3 catalyst and an impregnated benchmark Ni/MgO catalyst. At 260 degrees C and 20 bar under steady-state conditions the best performing catalyst with a nominal molar nickel-to-magnesium ratio of 50 : 50 reached 92% CO2 conversion with a CH4 selectivity close to 100% under stoichiometric conditions. This catalyst was then subjected to a range of temperatures, GHSVs and gas feed compositions for a 100 h time-on-stream resilience test showing no deactivation while effectively suppressing the competing RWGS reaction. The results suggest that coprecipitated NM catalysts are highly productive and stable surpassing industrial methanation Ni/Al2O3 catalysts in terms of activity, selectivity and GHSV endurance even under hydrogen deficient conditions.

The transformation of CO(2 )and green hydrogen into methanol presents a sustainable route for chemical and fuel production. Conventional methanol synthesis catalysts, such as Cu/ZnO/Al2O(3), employ Al2O(3) as a structural promoter, while Ga(2)O(3 )has recently emerged as a promising alternative. This study compares Cu-based catalysts supported on Al2O(3 )(CA) and Ga2O(3 )(CG), prepared via coprecipitation of layered double hydroxide precursors with identical molar Cu:M (M = Al or Ga) ratio of 70:30. Using in situ and operando X-ray absorption spectroscopy and X-ray powder diffraction, we investigate the structural and redox dynamics of Ga during activation and CO2 hydrogenation. Gallium from its precursor state undergoes several phase transitions. At elevated temperatures, Ga exhibits redox activity, transitioning from Ga(3+ )to metallic Ga0 and forming CuxGay alloys at 480 degrees C, followed by de-alloying and re-oxidation at even higher temperatures. Our results suggest that the beneficial role of Ga reported in literature arises from metal-oxide interfacial effects rather than bulk alloying. Excess Ga2O(3) leads to low conversion levels and pronounced deactivation compared to the Al2O3-supported Cu catalyst and thus should be prevented. These findings highlight the importance of controlling promoter loading and dynamic behavior in catalyst design to optimize activity, stability, and selectivity for CO2-to-methanol conversion.

CoFe 2 O 4 (CFO) nanoparticles were synthesized via controlled co‐precipitation with subsequent calcination at 400 °C, 500 °C, and 600 °C to systematically investigate the influence of thermal treatment on mesostructure, catalytic performance, and especially defect landscape. Structural characterization revealed enhanced crystallinity, sintering, and reduced defect concentration with increasing calcination temperature. Mössbauer spectroscopy and magnetometry indicated increased inversion parameters, improved magnetic alignment, and reduced spin canting, which is consistent with enhanced atomic diffusion during calcination and structural ordering. Positron annihilation lifetime spectroscopy confirmed a calcination‐dependent decrease in vacancy‐type defects. Catalytic testing showed diverging trends: chemical water oxidation (CAN test) activity increased with calcination temperature, but electrochemical oxygen evolution (OER) activity decreased. The opposing behavior is attributed to distinct differences in mechanism: CAN test reactivity is dominated by surface site availability, whereas OER benefits from defect mediated conductivity and charge‐transfer. These results underline the pivotal role of defect engineering while tailing spinel catalysts and highlight that optimal mesostructures depend strongly on the target reaction.

In this study, the crystallization of a coprecipitated precursor for a Ni catalyst suitable for green methanation is investigated. The catalyst is derived from a basic hydroxycarbonate where Ni2+ is partially replaced by Mg2+-cations forming a mixed solid-solution crystal of the composition (Ni1-yMgy)12(CO3)8(OH)6O·mH2O (with y = 0-0.5). The hydrothermal aging was identified as a key step in its synthesis, which previously remained unexplored. Ex situ PXRD, IR, EDX, SEM, and ICP-OES as well as in situ IR and pressure monitoring were used to study this reaction. In this aging step, the amorphous precipitate begins to transform into a crystalline solid-solution compound within 30 min after reaching hydrothermal conditions. The initial amorphous precipitate was examined, and its sum formula was established as (Ni1-xMgx)2(CO3)(OH)2·2.5H2O. The multimethod approach clarified the metal ion ratio evolution and the crystallization and carbonate incorporation as a function of time as the two hydroxycarbonate phases interconverted, enhancing understanding of the aqueous precursor chemistry and catalyst synthesis and showing the importance of dissolved species in the mother liquor in this reaction.

The perovskite-based catalysts LaFeO3 (LFO) and LaFe0.75Co0.25O3 (LFCO) were examined to elucidate the reaction mechanism and disentangle the complex surface phenomena occurring during the seemingly simple CO oxidation reaction. Precise kinetic measurements and operando spectroscopy were employed to explain the interplay between the formation of surface intermediates and the transformations of the surface sites, leading to the occurrence of a frustrated-phase transition at the surface that can potentially define the catalyst activity under different reaction conditions. Our work specifically highlights the effect of partial cobalt substitution into the perovskite's structure on improving the activity of the reference LFO. Modulation-excitation spectroscopy coupled with phase-sensitive detection (MES-PSD) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) were employed at different temperatures to elucidate the multifaceted role of cobalt in promoting the carbonate-mediated pathway for CO oxidation. For LFO, kinetic and theoretical analyses confirm a pure Mars-van Krevelen (MvK) mechanism mediated by bidentate carbonates, yielding low activity but high stability. In contrast, LFCO exhibits higher activity despite slight deactivation through a dual MvK/Langmuir-Hinshelwood (LH) pathway. Monodentate carbonates act as low-temperature and unstable intermediates, with LFCO accelerating carbonate-to-CO2 conversion via enhanced surface oxygen mobility. The temperature also dictates mechanistic shifts: LH dominates below 170 degrees C, while MvK prevails above this threshold. Additionally, operando NAP-XPS reveals that this transition coincides with cobalt reduction, iron oxidation, and a possible frustrated-phase transition that activates carbonate intermediates. In our catalytic systems, cobalt serves as the primary active site, while lanthanum stabilizes the perovskite structure and surface carbonates, and iron maintains charge balance. The interplay between the sites is essential to achieve a higher conversion. These findings demonstrate how composition and temperature govern dynamic surface restructuring and reaction pathways in perovskite catalysts.

The utilization of renewable hydrogen that was transported and stored as green ammonia relies on a highly efficient ammonia decomposition catalyst. Industrial demand for high-purity hydrogen requires operation at high temperature of at least 500 °C due to the endothermicity of the reaction. At these conditions, abundant Ni/MgO catalysts with nanoparticles larger than 5 nm are not limited by the widely studied N-N recombination, but the rate-determining step (RDS) has changed to ammonia dehydrogenation. A combined experimental and theoretical study on size-controlled Ni/MgO catalysts explains this behavior in a dual-site / dual-RDS model by the interplay of a size-induced lack of edge sites that are active in ammonia dehydrogenation, and an increase in the free energy barrier of this step relative to the N-N recombination. Catalyst design thus needs to aim at a stabilization of an optimal Ni nanoparticle size at high reaction temperatures to balance the two possible kinetic limitations by an optimal relative abundance of the edge sites active in ammonia dehydrogenation and the B5 sites for N-N recombination. Such stabilization is demonstrated for co-precipitated and ex-solved Ni/MgO catalysts where the optimal size is determined to be 5-6 nm. Future catalyst development for high-temperature ammonia decomposition should target the promotion of the ammonia dehydrogenation sites on larger particles and /or the modification of smaller particles to facilitate the N-N recombination step.

Powder catalysts are widely applied in electrocatalysis, however compared to composition or other synthesis parameters, the drying conditions during synthesis are rarely studied in detail or optimized, despite their significant influence on material properties and electrochemical performance. In this work, the effects of freeze drying, airflow drying, oven drying and a combined airflow-oven-drying procedure were investigated using the same batch of co-precipitated NiFe-LDH. The combined airflow-oven-drying approach proves advantageous, yielding smaller particles with a larger surface area of 216 m2/g and improved dispersion stability. As a result, desired mass loadings can be consistently achieved while maintaining beneficial properties through the thermal curing step and strengthening aggregate cohesion. While this approach only results in a modest performance improvement in GC-RDE measurements compared to oven and airflow-drying, during binder-free measurements on nickel the coating homogeneity as well as catalyst retention are substantially improved along with a 26-40 mV reduction of the OER overpotential at 50 mA/cm2. In contrast, freeze-drying yields particles with a surface area of 146 m2/g but leads to inferior GC-RDE performance and poor catalyst retention for binder-free nickel electrodes. These findings highlight the potential for optimizing catalyst performance through tailored drying conditions and may explain the large scattering of literature results based on synthetic procedures where such parameters are frequently neglected.

In this study, the catalytic decomposition of 2-propanol to acetone was investigated over Co3O4 catalysts, with a specific focus on the role of water and its derivatives in the reaction mechanism and the overall catalytic activity of this process. Two types of catalysts were addressed in this study: the powdered materials investigated under ambient pressure conditions and their model Co3O4(111) counterparts studied in ultrahigh vacuum (UHV) following a rigorous surface science approach. Pretreatment of both types of catalysts with water at elevated temperatures was shown to result in a substantial increase in the acetone formation rate. Results obtained by a combination of scanning tunneling microscopy (STM) and infrared reflection absorption spectroscopy (IRAS) revealed that pretreatment of the Co3O4(111) model surface with water at elevated temperatures leads to the formation of isolated hydroxyls (OsH) involving a lattice oxygen atom (Os). In contrast, water deposition at lower temperatures results in the formation of an extended, partly dissociated OH/H2O network layer exhibiting short-range order. The isolated OsH groups obtained after high-temperature pretreatment with water were observed to play a key role in H abstraction, both from molecular 2-propanol and from the propoxy reaction intermediate, leading to efficient formation of the target product acetone. In contrast, on the surface depleted of isolated OsH species, both H abstraction steps become strongly inhibited. Importantly, dissociation of both 2-propanol and the propoxy reaction intermediate takes place only when the hydroxyl groups are present as isolated OsH species, which are not integrated into an extended, partly dissociated OH/H2O network: if the OH/H2O network was formed prior to the reaction, both H abstraction steps were observed to be nearly completely suppressed despite the presence of substantial amounts of adsorbed 2-propanol. The role of the isolated OsH groups can most likely be attributed to their function as hydrogen acceptors for H atoms leaving from either 2-propanol or the propoxy intermediate. Our results also suggest that the isolated OsH group appears to be a substantially more efficient hydrogen acceptor than the adsorbate-free lattice oxygen Os.

Understanding a catalytic reaction requires tools that elucidate the structure of the catalyst surface and subsurface, ideally at atomic resolution and under reaction conditions. Operando electron microscopy meets this requirement in some cases, but fails in others where the required reaction conditions cannot be reached or lead to an unwanted influence of the electron beam on the reactant and catalyst. We introduce ILIAS (identical location imaging and spectroscopy) in combination with a quasi in situ approach to disentangle the effect of heat and gas on the surface of nanoparticles from the effect of the electron beam. With this approach we allow high temperatures and pressures in any gaseous environment on the one hand, and atomic resolution imaging and spectroscopy on the other. As a proof of concept, we resolve the structural evolution of a Co3O4 spinel catalyst using ILIAS and track the oxidation state across the surface before and after heating in a reductive or oxidative environment. We then titrate the surface of the catalyst using CO as a probe molecule to remove highly active oxygen species formed during the thermal treatment, providing unprecedented insight into the interplay between pretreatment and surface reactivity of Co3O4 nanoparticles.

The "crude oil exodus" and energy transition will finally hinge on the availability of hydrogen. Catalytic processes like the water-gas shift (WGS) reaction may significantly contribute to its production and become crucial for utilizing alternative feedstocks. This work demonstrates how thiolate-protected gold nanoclusters can be employed as precursors for single-atom alloy (SAA) catalysts. The clusters serve as carriers of heteroatom dopants (Cu, Pd) while precisely maintaining 25 metal atoms per cluster (<1 nm). Using the 2PET ligand during synthesis led to high yield and cluster stability, but ligand exchange was required to link clusters to a ZnO support efficiently. Introducing pMBA as a ligand enabled a homogeneous cluster distribution on the ZnO surface, creating a well-defined catalyst with dual functionality. This SAA catalyst, outperforming a Cu/ZnO/Al2O3 benchmark in WGS, may get industrial relevance when upscaled while still serving as a well-defined model system in catalysis. Thereby, it bridges the gap between practical applications and fundamental research. Pre- and postreaction analysis by XPS proved the presence of the dopants in the catalysts in the expected stoichiometry, showed changes in the electronic structures, but also revealed sulfur migration from the clusters/ligands to the support, forming ZnS. Furthermore, XPS unveiled a pretreatment-induced SMSI decoration effect, stabilizing the small particles during catalysis. (S)-TEM indicated a homogeneous cluster distribution on ZnO after synthesis and proved small particle sizes throughout the experiments. In situ DRIFTS confirmed the accessibility of the dopant atoms by the reactant CO and also detected adsorbed byproducts. The precise size and doping control of thiolate-protected SAA nanoclusters, together with their catalytic performance, demonstrate the potential for targeted future investigations in a wide range of industrial applications.

Ammonia, industrially produced by the Haber–Bosch process, can serve as a promising renewable energy carrier based on its high hydrogen content and energy density as well as its full-fledged infrastructure worldwide for transportation. Renewable hydrogen will be converted firstly in ammonia synthesis, stored and/or transported bound in ammonia, and released on demand by ammonia decomposition. So far, the most active catalysts for the decomposition reaction are Ru-based due to its optimal nitrogen binding energy compared to other transition metals. However, due to the high cost of Ru, the development of alternative catalysts for ammonia decomposition is attractive, especially non-noble transition metals such as Fe, Ni, or Co. For supported metal catalysts, size and support effects play important roles in the catalytic reaction, resulting in a change of their geometric and/or electronic properties. In this review, we first discuss and comment on representative existing studies of the size and support effects of Ru, Fe, Ni, and Co catalysts in ammonia decomposition from an experimental and theoretical view, suggesting possible reasons for geometrical and electronic effects. Afterward, we will summarize the available catalytic data in the literature in the form of TOF H2 and reaction rate of each supported transition-metal catalyst with different supports as a function of the particle size, attempting to identify an optimum particle size and a trend for the different supports. Finally, we will discuss the challenges and perspectives of future-oriented research on the size and support effect in ammonia decomposition.

The increasing demand for hydrogen production has driven interest in ammonia decomposition. Iron-based catalysts, widely used for ammonia synthesis, exhibit suboptimal performance in the reverse process due to their tendency to form iron nitrides. Recent experiments have shown that alloying iron with cobalt enhances the catalytic activity (Chen et al., Nat. Commun. 15, 871, 2024), yet the microscopic origin of this promotional effect is not fully understood. To address this, we leverage recent developments in machine learning-based molecular dynamics simulations to investigate the key reactions of the catalytic cycle, fully accounting for dynamical lateral interactions on the catalyst surface. Our simulations reveal that cobalt alloying provides a dual promotional effect: it slightly lowers the free energy barrier for nitrogen recombination, which is the rate-determining step for ammonia decomposition on iron, while significantly suppressing nitrogen migration into the bulk, thereby preventing nitride formation. These insights are supported by complementary transient decomposition experiments and desorption measurements, which confirm the enhanced activity and resistance to nitridation in FeCo alloys compared to monometallic iron catalysts. Furthermore, long-term stability tests demonstrate that the FeCo catalyst sustains high ammonia conversion over extended time scales. By capturing the complex interplay of competing dynamical processes at the atomic scale, our results highlight the importance of going beyond static structure-property relationships to gain mechanistic insights that can guide the rational design of more robust and efficient catalysts.

The novel crystalline bimetallic single-source precursor (Ni1-xMgx)12(CO3)8(OH)6O · y H2O with x = 0-0.5 can be converted into a highly active Ni/MgO CO2 methanation catalyst. All stages of preparation, namely, coprecipitation, crystallization, calcination, and reduction, as well as the spent catalysts have been comprehensively analyzed using powder X-ray diffraction, physisorption, transmission electron microscopy, and other techniques. The scalable synthesis allows attaining unusually high surface areas around 230 m2 g-1 for the calcined precatalyst Ni1-xMgxO. During reduction, this oxide solid solution separates into metallic Ni and Ni-depleted oxide to form the active catalyst with finely interdispersed nanoparticles of both components with a high porosity. A high methane production rate is observed in a CO2/H2 (1:4) feed at high space velocities of ≈150 Lh-1 g-1. This performance is competitive with an industrial methanation catalyst and depends strongly on the Ni:Mg ratio utilized in the synthesis. For an equimolar ratio, the new catalyst is found to be 4 times as active as the benchmark. Due to the nanoscaled microstructure, the novel material can stabilize very high Ni loadings (≤77 wt%) with only minor sintering effects at a reaction temperature of 240-280 °C. This material thus closes the gap between thermally unstable Raney-type and conventional lower loaded impregnated industrial catalysts.

The aerobic liquid-phaaCo0.7Fe0.3O3 perovskite under mild conditions exhibited an enhanced selectivity toward KA oil (mixture of cyclohexanol and cyclohexanone) at high conversion. Mechanistic investigations revealed a partial reduction of Co3+ to Co2+ in the surface region during the activation of the C-H bond. The selectivity differences induced by adding the catalyst were qualitatively analyzed using in situ ATR-IR spectroscopy. The radical scavenging studies and spin trap EPR confirmed the crucial role of cyclohexylperoxyl (C6H11OO center dot), cyclohexyloxyl (C6H11O center dot), hydroxyl (HO center dot) and cyclohexyl (C6H11 center dot) radicals in the reaction. Scavenging C6H11OO center dot during the uncatalyzed reaction strongly increased the stability of KA oil. Postreaction characterization by XRD, XPS, TPR, Mossbauer, magnetometry, EPR, and Raman spectroscopy confirmed the partial reduction of Co3+ and the formation of an additional Co-rich LDH phase during cyclohexane oxidation. DFT calculations of the cyclohexyl hydroperoxide (CHHP) decomposition pathways provided evidence that alpha -H abstraction is highly favored (33 kJ/mol) compared with the homolytic O-O cleavage (127 kJ/mol) in the absence of a catalyst and validated the influence of the catalyst on the homolytic O-O cleavage of CHHP via the Haber-Weiss reaction. A catalytic cycle based on mixed oxyhydroxy Co dimers is proposed to rationalize the influence of the catalyst in controlling highly oxidizing C6H11OO center dot radicals, thus favoring KA oil stability.

Transition metal oxides are excellent catalysts for selective oxidation reactions, which are a prominent source of industrially relevant chemicals. However, these reactions suffer from multiple competing reaction pathways, limiting the selectivity. Thus, it is essential to gain an understanding of the underlying processes occurring on the catalyst that affect its performance. Here we synergistically combine operando X-ray spectroscopy and operando transmission electron microscopy to unravel a network of solid-state processes that controls the catalytic properties of Co3O4 in the oxidation of 2-propanol towards acetone. These include exsolution, diffusion and defect formation, which strongly distort the catalyst lattice at lower temperatures. Ultimately, they also lead to a maximum in acetone selectivity when the catalyst is trapped in a frustrated or metastable state at the onset of crystallization of the exsolved particles to CoO and void formation, which coincides with the maximum in surface cobalt oxidation state in the spinel.

While TiS2 has been extensively studied for its ability to intercalate alkali metals like Li or Na, the higher homologue ZrS2 was studied only sparsely. Furthermore, an influence of different coordinating and noncoordinating electrolyte solvents on cyclability as well as the structural changes of the host structures had been observed for different active materials. In this study, we therefore investigated the intercalation mechanism of Na+ ions into layered 1T-ZrS2 using electrolytes with solvents of different coordination strengths toward Na+, namely sodium trifluoromethanesulfonimide in ethylene carbonate and diethyl carbonate (1:1, EC/DEC) and sodium triflate in bis(2-methoxyethyl) ether (diglyme). At low intercalation degrees, coordinating solvents (e.g., diglyme) lead to a cointercalation in combination with a large expansion of the interlayer distance. After deintercalation, a turbostratically disordered material was obtained. In contrast, for weakly coordinating solvents (EC/DEC) no cointercalation was observed which enabled us to observe the reversible phase transitions from 1T-ZrS2 to 3R-NaZrS2 upon (de)intercalation. This transition proceeds via stacking faults and was analyzed in detail. Further, the intermediates of the electrochemical intercalation were analyzed by solid-state NMR and cycling stability tests were carried out. The long-term stability of cells prepared from ZrS2 is comparable, independent of the electrolyte solvent.

Ga has an ionic radius fitting the radius of Zn much better than Al, which makes it an interesting candidate for doping of ZnO, which is relevant in context with Cu/ZnO-catalysts and with transparent conductive oxides. Here, the structural changes of Ga-doping of nano-scale ZnO, which is obtained via thermal decomposition of hydrozincite, are studied by a combination of X-ray diffraction, 71Ga/1H MAS NMR, quantum-chemical calculations and electron microscopy techniques. By quantum chemical calculations the NMR fingerprint of different Ga point defects is predicted, the calculations are validated against experimental data for different crystalline compounds. The relevant point defect in ZnO could be identified by the point symmetry of the isolated defect and comparison to the calculated values. The kinetic solubility limit for Ga in ZnO is determined by X-ray diffraction and NMR. It is shifted to higher values as compared to the Al variant. Finally, the distribution of Ga and H atoms within the nano-scale material is studied by "paramagnetically assisted surface peak assignment" (PASPA) NMR, REDOR and electron microscopy which shows that for Ga substitution ratios above the solubility limit the excess of Ga is incorporated into a heavily disordered or amorphous, hydrogen-rich surface-layer.

In alkaline water electrolysis (AWE), anode wettability plays a critical role in governing bubble dynamics at the anode-electrolyte interface. Effective bubble management is essential for improving AWE performance, as it enhances active site accessibility and reduces transport resistance. This study investigates the influence of superlyophilicity and superlyophobicity of spray-coated nickel iron layered double hydroxide (Ni-Fe-LDH) anodes on the electrochemical performance for the oxygen evolution reaction (OER). Surface wettability is adjusted through binder selection (Sustainion and Nafion) and drying-induced morphological modifications. Sustainion-based nanostructured anode layers display pronounced superlyophilicity (θ < 10°) governed by the Wenzel model. In contrast, Nafion-based nanostructured films exhibit tailored superlyophobicity (θ > 150°) indicative of a Cassie-Baxter-type wetting state. The superlyophilic anodes achieve the lowest overpotential, with a reduction of 73 mV at 100 mA cm-2 compared to the superlyophobic anode. Postelectrochemical analysis reveals a correlation between wetting states and the extent of the anode's active area utilization. Superlyophilic anodes achieve a complete wetting and full layer contribution, while superlyophobic anodes exhibit large nonwetted regions as high as ≈47%, resulting in partial contribution to the OER. The understanding gained by this work enables the rational design of high-performance anodes through the systematic control of wettability.

The structural and electronic effect of Al and Ga as ternary metals in Cu/ZnO catalysts for the methanol synthesis was examined. For this purpose, three zincian malachite-derived catalysts with the nominal Cu:Zn ratio of 70:30 were synthesized: an unpromoted binary catalyst (CZ) and two ternary catalysts with either 3 mol% Al (CZA) or Ga (CZG). Both Al and Ga showed a strong impact on the catalyst's structure. Alongside the catalyst's evolution from the co-precipitated precursors phase to the activated and reduced state, an improved microstructure and an increased BET surface area were found for the secondary promotor (Al or Ga) containing catalysts. Moreover, a sequence of chemisorption experiments allowed us to quantify and differentiate between Cu-surf and Zn-red surface species in the activated catalysts. Considering the specific copper surface areas, DRIFTS data and catalytic results, an additional electronic promotion of Al and Ga is proposed. As demonstrated by Ga K-edge XANES, this promotion effect is related to doping of the ZnO support and enhances the reducibility of ZnO to form more Zn-red sites. This effect is stronger for Al leading to a more pronounced Zn-red overlayer on the Cu surface due to SMSI. In methanol synthesis, this results in a performance order CZA > CZG > CZ.