In the era of the energy transition, the development of sustainable, high-performance, and multifunctional catalysts that adapt to complex catalytic processes is essential. Here, we report shapeshifting bimetallic iron-nickel catalysts developed via an exsolution strategy for carbon dioxide-mediated ethane conversion. By controlling the reduction temperature of a perovskite host, either alloyed iron-nickel nanoparticles or oxide-alloy core-shell nanoparticles are selectively formed. Oxidative regeneration of the perovskite enables reversible interconversion between these distinct nanostructures within the same parent material. As a result, the catalyst exhibits switchable selectivity between ethane dry reforming and carbon dioxide-assisted oxidative dehydrogenation while maintaining high stability. Repeated redox cycling confirms that the structural transformation and catalytic performance are largely reversible. These results demonstrate that exsolution provides a robust platform for designing regenerable catalysts with deliberately tunable and switchable catalytic states.

In this work, we examine the redox behavior and exsolution kinetics of Ni and Fe in A-site-deficient Sr0.95Ti1-x+yFexNiyO3 +/-delta, combining TPR, XAS, electron microscopy and EPR to elucidate dopant-specific contributions to defect chemistry and metal nucleation. In particular, TPR data indicated that Fe predominantly governs the formation and reducibility of oxygen-vacancy-associated defects, generating reduced Fe species at comparatively low temperature, whereas Ni dictates the overall reduction extent. In fact, as assessed by XAS, Ni-only samples exhibit relatively low conversion to Ni(0), while co-doping with Fe boosts Ni exsolution. Moreover, it turned out that even a tiny Ni amount promotes iron reduction, as unveiled by EXAFS. Along this line, STEM analyses confirmed the surface segregation of well-anchored Fe-Ni co-exsolved nanoparticles for co-doped perovskites, while scarce exsolution was observed for Fe-doped samples. EPR completed the picture corroborating that Fe species, incorporated in the perovskite as highly stable Fe(iii) substitutional defects, are less reducible and less mobile than Ni ones, which instead appear mostly as intercalated sites. Such Fe defects become mobile and undergo surface segregation only when Ni is incorporated in the lattice. These structure-property relationships directly translate into enhanced performance in the RWGS reaction of co-doped perovskites, where Fe drives vacancy-mediated redox processes while Ni promotes H2 dissociation. Overall, the results indicate that the methodological approach developed here can be extended to other exsolvable dopants (e.g., Co), offering a pathway toward the rational design of exsolved catalysts with tunable structures and compositions for advanced energy-conversion applications.

Driven by the growing demand for in situ and in operando investigations of structural transformations under complex stimuli, we present versatile and compact sample environments developed for synchrotron-based small-angle and wide-angle X-ray scattering (SAXS/WAXS) experiments. The setups combine multi-parameter control, enabling simultaneous control of temperature (up to 1000 °C), gas atmosphere, light irradiation, and nearly 360° sample rotation. These capabilities facilitate real-time monitoring of nanoscale processes, including nanoparticle exsolution in perovskites and phase transitions of confined liquid crystals under UV illumination. The integration of multi-parameter controls within compact and modular cells overcomes significant technical challenges, expanding experimental capabilities at the P62 beamline of PETRA III. Our developments provide a versatile platform for investigating stimuli-responsive materials under realistic conditions, enhancing understanding of structure–property relationships and informing the design of advanced functional materials across catalysis, energy storage, and soft matter physics.

The development of future energy conversion devices passes inevitably through the improvement of the mass transport and oxygen exchange of the oxygen electrode. Herein, we show how nanoporosity can be used to enhance reducibility and thereby oxygen evolution in LaMnO 3 and how it influences the electronic transport in the material. An ordered nanoporous LaMnO 3 thin film (thickness 80 nm, pore size 25 nm) was prepared by the sol–gel approach using block copolymer templating. At high temperature, the Mn 2p X‐ray photoelectron spectroscopy (XPS) showed increased reduction of Mn to Mn 3+ and Mn 2+ for nanoporous LaMnO 3 compared to its dense counterpart at 400 °C, indicating larger release of oxygen due the high surface‐to‐volume ratio of the material. In turn, the electrical resistivity of the material increased by 10 times and the activation energy of the electronic conductivity by 15%, as shown by finite element method (FEM) simulations and impedance spectroscopy analyses. This effect was attributed both to the tortuous path induced by the nanoporosity and to the spontaneous electronic conductivity decrease, i.e., hole consumption, consequent to the extensive material reduction.

The work presented herein reports on the investigation of the biogas dry reforming catalytic performance of LaNiO3 (LNO), La0.8Sm0.2NiO3 (LSNO), La0.8Pr0.2NiO3 (LPNO) and La0.8Ce0.2NiO3 (LCNO). The perovskite-type materials were synthesized via citrate sol-gel and characterized using XRD, N2 physisorption H2-TPR, H2-TPD, TEM, HAADF-STEM and XPS. The performance of all catalysts in terms of both activity and stability was examined in order to assess the effect of temperature on the CH4 and CO2 conversion, as well as on the H2 and CO yield and the H2/CO molar ratio of the produced gas mixture. Experimental results showed that modification of LaNiO3 with Sm and Pr enhances the catalytic performance in terms of catalytic stability and reduces the order/ crystallinity of the deposited coke. A theoretical model has also been produced in Python with the purpose of simulating the catalytic performance. Modelling results showed a good agreement with the experimental values and therefore confirm the validity of the model for predicting the dry reforming catalytic performance.

The surface transformation and defect evolution of Cu-doped SrTiO3 upon copper exsolution have been studied by exploiting a multi-technique approach which integrates, for the first time, common methods describing exsolution like XAS, XPS and STEM with unconventional strategies, namely electron paramagnetic resonance (EPR) and UV-Vis diffuse reflectance (UV-DRS). XAS and EPR indicated that copper is present in the matrix in a disordered coordination environment as amorphous Cu2O and CuO located at the surface and as substitutional Cu2+ lattice species with a distorted octahedral structure. Interestingly, EPR unveiled that, during exsolution, Cu2+ surface sites with disordered coordination primarily migrate undergoing selective reduction, while a delay is observed for the lattice defects. UV-DRS resulted in a valid alternative to HRTEM to determine the size of exsolved nanoparticles by tracking the plasmon resonance effect. Moreover, when XANES showed the complete regain of the pristine state of Cu after reoxidation, both UV-DRS and EPR highlighted that the original features are not entirely restored. These outcomes suggest that the chemical environment of exsolvable species is much more heterogeneous and the exsolution process much less straightforward than expected. Thus, alternative and original characterization techniques should be exploited to provide a solid methodological benchmark for an effective evaluation of this phenomenon.

Chemical looping reforming coupled with CO2 splitting is a promising CO2 utilization method that produces a valuable fuel. Here, we present a novel perovskite oxide with the composition of La0.6Ca0.4Fe0.95M0.05O3-delta (M = Ni, Co, Ni-Co) that functions both as an oxygen carrier and as a redox catalyst. Using a multi technique approach with HR-TEM, XRD, XAS, and Mossbauer spectroscopy, we find that alloy nanoparticles spontaneously form on the surface of Ni-Co doped carriers in a CH4 atmosphere, and as they are repeatedly exposed to CO2 and CH4 during the chemical loop, Fe atoms move back and forth between the inside (as Fe cations in the lattice) and the outside (as a part of metallic alloy) of the host scaffold. Eventually, the co-doped samples become highly reactive towards both gases and have excellent coking and redox stability, demonstrating record-level syngas yield (total similar to 10 mmol/g) at 850 degrees C, over 50 redox cycles.

Nanoporosity is clearly beneficial for the performance of heterogeneous catalysts. Although exsolution is a modern method to design innovative catalysts, thus far it is predominantly studied for sintered matrices. A quantitative description of the exsolution of Ni nanoparticles from nanoporous perovskite oxides and their effective application in the biogas dry reforming is here presented. The exsolution process is studied between 500 and 900 °C in nanoporous and sintered La0.52 Sr0.28 Ti0.94 Ni0.06 O3±δ . Using temperature-programmed reduction (TPR) and X-ray absorption spectroscopy (XAS), it is shown that the faster and larger oxygen release in the nanoporous material is responsible for twice as high Ni reduction than in the sintered system. For the nanoporous material, the nanoparticle formation mechanism, studied by in situ TEM and small-angle X-ray scattering (SAXS), follows the classical nucleation theory, while on sintered systems also small endogenous nanoparticles form despite the low Ni concentration. Biogas dry reforming tests demonstrate that nanoporous exsolved catalysts are up to 18 times more active than sintered ones with 90% of CO2 conversion at 800 °C. Time-on-stream tests exhibit superior long-term stability (only 3% activity loss in 8 h) and full regenerability (over three cycles) of the nanoporous exsolved materials in comparison to a commercial Ni/Al2 O3 catalyst.

Ni/LnO(x)-type catalysts (Ln = La, Ce, Sm or Pr, denoted as LNO, CNO, SNO and PNO, respectively) were prepared via a citrate sol-gel method, characterized, and evaluated for the dry reforming of biogas. For the calcined catalysts, the formation of LaNiO3 perovskite crystallites with high purity was observed in the case of La, whereas NiO-LnO(x) mixed oxides were obtained for the other lanthanides. The reduction treatment led to the formation of medium-sized (similar to 15 nm) and highly dispersed Ni nanoparticles in LNO following the decomposition of the LaNiO3 perovskite, in contrast to the other catalysts, where bigger Ni crystallites were formed (similar to 30 nm). As a result, LNO was shown to possess a higher catalytic activity in comparison to the other materials. Regarding the catalytic stability, LNO displayed a considerable activity loss followed by a high pressure drop due to reactor blockage, meaning that the use of Sm (Ni/Sm2O3) can be considered as an alternative strategy to restrict catalyst deactivation. As evidenced by the characterization of the spent catalysts, the deactivation for the most part can be attributed to the extensive coke deposition over the catalysts. The coke deposited was found to be both in the form of more disordered/amorphous carbon, as well as in the form of highly crystalline and multi-walled carbon nanotubes. Crown Copyright (c) 2023 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. All rights reserved.

Recently, the significant improvements in polymer composites properties have been mainly attributed to the ability of filler nanoparticles (NPs) to self-assemble into highly anisotropic self-assembled structures. In this work, we investigate the self-assembly of core-shell NPs composed of a silica core grafted with polybutadiene (PB) chains, generating the so-called "hairy" NPs (HNPs), immersed in tetrahydrofuran solvent. While uncoated silica beads aggregate forming uniform compact structures, the presence of a PB shell affects the silica NPs organization to the point that by increasing the polymer density at the corona, they tend to self-assemble into linear chain-like structures. To reproduce the experimental observations, we propose a theoretical model for the two-body that considers the van der Waals attractive energy together with the polymer-induced repulsive steric contribution and includes an additional three-body interaction term. This term arises due to the anisotropic distribution of PB, which increases their concentration near the NPs contact region. The resulting steric repulsion experienced by a third NP approaching the dimer prevents its binding close to the dimer bond and favors the growth of chain-like structures. We find good agreement between the simulated and experimental self-assembled superstructures, confirming that this three-body steric repulsion plays a key role in determining the cluster morphology of these core-shell NPs. The model also shows that further increasing the grafting density leads to low-density gel-like open structures.

In this paper, we show how the composition of bimetallic Fe-Ni exsolution can be controlled by the nature and concentration of oxygen vacancies in the parental matrix and how this is used to modify the performance of CO2-assisted ethane conversion. Mesoporous A-site-deficient La0.4Sr0.6-αTi0.6Fe0.35Ni0.05O3±δ (0 ≤ α ≤ 0.2) perovskites with substantial specific surface area (>40 m2/g) enabled fast exsolution kinetics (T < 500 °C, t < 1 h) of bimetallic Fe-Ni nanoparticles of increasing size (3-10 nm). Through the application of a multitechnique approach we found that the A-site deficiency determined the concentration of oxygen vacancies associated with iron, which controlled the Fe reduction. Instead of homogeneous bimetallic nanoparticles, the increasing Fe fraction from 37 to 57% led to the emergence of bimodal Fe/Ni3Fe systems. Catalytic tests showed superior stability of our catalysts with respect to commercial Ni/Al2O3. Ethane reforming was found to be the favored pathway, but an increase in selectivity toward ethane dehydrogenation occurred for the systems with a low metallic Fe fraction. The chance to control the reduction and growth processes of bimetallic exsolution offers interesting prospects for the design of advanced catalysts based on bimodal nanoparticle heterostructures.

In this contribution brownmillerite-based nanocomposite cathode for Single-Chamber Solid Oxide Fuel Cells is developed. These cells can be very attractive especially for small and cheap devices because of the absence of seals. The efficiency of SC-SOFCs is strictly connected to the selectivity of anode and cathode, the bottleneck for this technology. The development of a cathode inert in fuel oxidation is particularly challenging. Our strategy is to start from a catalytically un-active support (CFA = Ca2FeAl0.95Mg0.05O5) and induce the formation of iron oxide based nanoparticles, expected to activate oxygen. Symmetric (CFA thorn FeOx/CGO/CFA + FeOx) and complete cells (CFA + FeOx/CGO/Ni-CGO) are studied in air and methane/oxygen 2:1 mixture. The Area Specific Resistance of CFA + FeOx is less than 1/3 that of CFA. The high selectivity allows to reach an efficiency of 25%; power still needs to be increased but we demonstrated the possibility to develop selective low cost electrodes. The effect of air, methane/oxygen exposure and the heat treatments were carefully investigated. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

"Hairy" nanoparticles (HNPs), i.e. inorganic NPs functionalized with polymer chains, are promising building blocks for the synthesis of advanced nanocomposite (NC) materials having several technological applications. Recent evidence shows that HNPs self-organize in a variety of anisotropic structures, resulting in an improvement of the functional properties of the materials, in which are embedded. In this paper, we propose a three-step colloidal synthesis of spherical SiO2-HNPs, with controlled particle morphology and surface chemistry. In detail, the SiO2 core, synthesized by a modified Stöber method, was first functionalized with a short-chain amino-silane, which acts as an anchor, and then covered by maleated polybutadiene (PB), a rubbery polymer having low glass transition temperature, rarely considered until now. An extensive investigation by a multi-technique analysis demonstrates that the synthesis of SiO2-HNPs is simple, scalable, and potentially applicable to different kind of NPs and polymers. Morphological analysis shows the overall distribution of SiO2-HNPs with a certain degree of spatial organization, suggesting that the polymer coating induces a modification of NP-NP interactions. The role of the surface PB brushes in influencing the special arrangement of SiO2-HNPs was observed also in cis-1,4-polybutadiene (cis-PB), since the resulting NC exhibited the particle packing in "string-like" superstructures. This confirms the tendency of SiO2-HNPs to self-assemble and create alternative structures in polymer NCs, which may impart them peculiar functional properties.

The morphology and structural changes of confined matter are still far from being understood. This report deals with the development of a novel in situ method based on the combination of anomalous small-angle X-ray scattering (ASAXS) and X-ray absorption near edge structure (XANES) spectroscopy to directly probe the evolution of the xenon adsorbate phase in mesoporous silicon during gas adsorption at 165 K. The interface area and size evolution of the confined xenon phase were determined via ASAXS demonstrating that filling and emptying the pores follow two distinct mechanisms. The mass density of the confined xenon was found to decrease prior to pore emptying. XANES analyses showed that Xe exists in two different states when confined in mesopores. This combination of methods provides a smart new tool for the study of nanoconfined matter for catalysis, gas, and energy storage applications.

Ladder-like silsesquioxanes (SSQs) and TiO2 have been functionalized with methacryloyloxypropyl chains and embedded in a polybutadiene (PB) matrix giving rise to hybrid (organic-inorganic) nanocomposites (NCs) capable of acting as oxygen scavenging materials. The joint use of infrared spectroscopy, small-angle X-ray scattering, and permittivity measurements highlighted that the presence of TiO2, regardless of its modification, does not significantly alter the structure of the NCs, but just reduces the crosslinking degree and induces a local disorganization of the ladder-like SSQ stacks. The introduction of an optimum amount (0.5 wt%) of modified TiO2 within the polymeric matrix enhanced the oxygen uptake rate of ca. 70% with respect to the sole polymeric material. Moreover, the uptake kinetics changes from the first to second order with respect to the PB amount, clearly indicating different oxidation mechanisms. NCs containing modified TiO2 showed an oxygen uptake rate ranging from 30 to 60% higher than that achievable in the presence of bare TiO2. The superior activity of the materials containing modified TiO2 has been related to mechanistic aspects. Fluorescence and electron spin resonance spectroscopies allowed to underline the role of singlet oxygen within the polymeric matrix, although the known photochemical oxidation of PB and the TiO2 induced hydroxyl radical mediated oxidation cannot be excluded. These results open the route to highly efficient flexible oxygen scavenging materials for the protection of electronic devices such as organic based light emitting diodes, solar cells, and liquid crystal displays, which require high targets of protection from oxygen and water.

In this work, a combined experimental and theoretical study of solid-liquid phase equilibria confined in mesoporous solids composed of spherical cages connected via smaller-sized cylindrical irregular channels is presented. The experimental data on phase equilibria obtained using nuclear magnetic resonance (NMR) cryoporometry with water as a probe liquid are analyzed using transition kernels developed for the spherical pores. They accurately predict the variation of the non-frozen water layer thickness with temperature as well as the positions of the solid-liquid and liquid-solid transition temperatures. By analyzing the melting and freezing transitions as well as scanning freezing transitions in materials with different properties of the interconnecting pore network achieved by different synthesis conditions, an accurate information on the textural properties and phase transition processes is obtained. The results obtained are compared to the structural information obtained using other experimental techniques such as small-angle X-ray scattering and gas sorption.

The design of nanoporous perovskite oxides is considered an efficient strategy to develop performing, sustainable catalysts for the conversion of methane. The dependency of nanoporosity on the oxygen defect chemistry and the catalytic activity of perovskite oxides toward CH4 and CO oxidation was studied here. A novel colloidal synthesis route for nanoporous, high-temperature stable SrTi0.65Fe0.35O3-δ with specific surface areas (SSA) ranging from 45 to 80 m2/g and pore sizes from 10 to 100 nm was developed. High-temperature investigations by in situ synchrotron X-ray diffraction (XRD) and TG-MS combined with H2-TPR and Mössbauer spectroscopy showed that the porosity improved the release of surface oxygen and the oxygen diffusion, whereas the release of lattice oxygen depended more on the state of the iron species and strain effects in the materials. Regarding catalysis, light-off tests showed that low-temperature CO oxidation significantly benefitted from the enhancement of the SSA, whereas high-temperature CH4 oxidation is influenced more by the dioxygen release. During isothermal long-term catalysis tests, however, the continuous oxygen release from large SSA materials promoted both CO and CH4 conversion. Hence, if SSA maximization turned out to efficiently improve low-temperature and long-term catalysis applications, the role of both reducible metal center concentration and crystal structure cannot be completely ignored, as they also contribute to the perovskite oxygen release properties.

Solution chemistry allows the crystallisation of range of iron oxides, including MFe2O4spinels, MFeO3perovskites and hexaferrites, such as BaFe12O19, with nanoscale crystallinity and properties suitable for fields such as catalysis and electronics.

The synthesis of a mesoporous (La,Sr) (Ti,Fe)O3-delta (LSTF) solid solution and its application as a catalytic support is presented. A mesoporous nanostructured perovskite solid solution with a tunable specific surface area and pore volume of up to 201 m(2) g(-1) and 0.411 cm(3) g(-1), respectively, was obtained by a sol-gel-like SiO2 endotemplating approach. Very high porosity combined with the redox-active characteristics of the perovskite structure makes these systems effective supports for Pt nanoparticle (NP) catalysts. As a result, when 0.8 wt % Pt NPs was introduced, the mesoporous LSTF showed improved CO and CH4 oxidation rates compared to commercially available SiO2 or CeO2. These observations demonstrate the promotional effects between Pt and LSTF and suggest an efficient strategy for achieving active support materials toward oxidation catalysis.