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The utilization of perovskite oxide as a catalyst for aqueous reactions is promising but challenging in stability. Here, we propose an in situ growth strategy that constructs an ultrathin protective skin on the Sr0.9Fe0.81Ta0.09Ni0.1O3‐δ perovskite surface and thus effectively solves the stability issue. Using a spherical aberration‐corrected transmission electron microscope, we observe the coexistence of an angstrom‐scale (~7 Å) Fe2O3 protective skin and FeNi alloy nanoparticles. A number of alloy nanoparticles grow along with the skin and uniformly take root on the skin surface. Such a hierarchical structure can reconstruct the surface electronic structure and suppress the ion leaching of perovskite oxide in water. Benefiting from this unique structure, the catalyst has experienced a substantial increase (800 h, more than three orders of magnitude) in its stable operation time in water (for example, in a hydrogen evolution reaction). These results provide valuable insight into solid‐solid phase transitions and have substantial implications for using structural defects at surfaces to modulate mass transport and transformation kinetics. Our strategy is sufficiently simple and can be used to subtly manipulate the catalyst structures to improve the performance of perovskite‐based catalysts and potentially other oxide catalysts for a wide range of reactions. [ABSTRACT FROM AUTHOR]

Zinc–air batteries (ZABs) hold significant promise for flexible electronics due to their high energy density and low cost. However, their practical application is hindered by the sluggish kinetics of the oxygen evolution and oxygen reduction reactions (OER/ORR). This study highlights a novel design of vertical graphene arrays (VGs) anchored on PrBa0.5Sr0.5Co1.8Ru0.2O5+δ (PBSCRu) perovskite nanofibers, fabricated via plasma‐enhanced chemical vapor deposition. Notably, the VG growth induces the exsolution of Co nanoparticles from the PBSCRu perovskite, resulting in a unique PBSCRu‐Co‐VG heterostructure. Theoretical calculations demonstrate that constructing PBSCRu‐Co‐VG heterojunction regulates interfacial electronic redistribution, thereby lowering energy barriers for both OER and ORR. As a result, the PBSCRu@VG‐5 electrocatalyst exhibits superior stability and higher peak power density in both liquid and flexible solid‐state ZABs compared to the pristine PBSCRu electrocatalyst. This protocol advances the integration of synergetic perovskite/metal/graphene composites, offering considerable potential for next‐generation energy conversion technologies. [ABSTRACT FROM AUTHOR]

Exsolution of metal nanoparticles (NPs) on perovskite oxides has been demonstrated as a reliable strategy for producing catalyst‐support systems. Conventional exsolution requires high temperatures for long periods of time, limiting the selection of support materials. Plasma direct exsolution is reported at room temperature and atmospheric pressure of Ni NPs from a model A‐site deficient perovskite oxide (La0.43Ca0.37Ni0.06Ti0.94O2.955). Plasma exsolution is carried out within minutes (up to 15 min) using a dielectric barrier discharge configuration both with He‐only gas as well as with He/H2 gas mixtures, yielding small NPs (<30 nm diameter). To prove the practical utility of exsolved NPs, various experiments aimed at assessing their catalytic performance for methanation from synthesis gas, CO, and CH4 oxidation are carried out. Low‐temperature and atmospheric pressure plasma exsolution are successfully demonstrated and suggest that this approach could contribute to the practical deployment of exsolution‐based stable catalyst systems. [ABSTRACT FROM AUTHOR]

Due to its abundant resources and advantages in transportation and storage, methane fueled solid oxide fuel cells (SOFCs) are highly needed. In this work, an exceptional internal reforming catalyst comprising in-situ exsolved NiRu bimetallic nanoparticles and oxygen-deficient layered double perovskite LaBaMn 1.6 Ni 0.3 Ru 0.1 O 5+δ (r-LBMNR) was prepared. Compared to the cell with LaBaMn 1.6 Ni 0.4 O 5+δ (r-LBMN) catalyst, the cell with a Ru-doping r-LBMNR catalyst layer, exhibits superior peak power output of 336 mW cm−2 and better durability with a less decay rate of 0.014% per hour in CH 4 fuel. The enhanced electrochemical performance can be attributed to the high oxygen ion and electron conductivities of the catalyst and the coupling of Ni and Ru sites with the oxygen-deficient r-LBMNR matrix This coupling activates CH 4 and H 2 O, promotes the oxidation of C atoms in CH 4 molecules, and enables reversible hydrogen spillover, ultimately leading to the production syngas of CO(g) and H 2 (g). [Display omitted] • Trace Ru-doping facilitating the exsolution of nanoparticles. • LaBaMn 1.6 Ni 0.3 Ru 0.1 O 5+δ was modified with abundant O v and exsolved NiRu alloy. • Cell can operate stably over 220 h with a degradation rate of 0.014% h−1. [ABSTRACT FROM AUTHOR]

The aim of this work was to verify the possibility of forming Ni-Fe and Co-Fe alloys via topotactic ion exchange exsolution in Fe-infiltrated (La,Sr,Ce)0.9(Ni,Ti)O3-δ or (La,Sr,Ce)0.9(Co,Ti)O3-δ ceramics. For this purpose, samples were synthesized using the Pechini method and then infiltrated with an iron nitrate solution. The reduction process in dry H2 forced the topotactic ion exchange exsolution, leading to the formation of additional round-shape structures on the surfaces of grains. EDS scans and XRD analysis confirmed the formation of bimetallic alloys, which suggests that these materials have great potential for further use as anode materials for Solid Oxide Fuel Cells (SOFCs). [ABSTRACT FROM AUTHOR]

The aim of this work was to verify the possibility of forming Ni-Fe and Co-Fe alloys via topotactic ion exchange exsolution in Fe-infiltrated (La,Sr,Ce)0.9(Ni,Ti)O3-δ or (La,Sr,Ce)0.9(Co,Ti)O3-δ ceramics. For this purpose, samples were synthesized using the Pechini method and then infiltrated with an iron nitrate solution. The reduction process in dry H2 forced the topotactic ion exchange exsolution, leading to the formation of additional round-shape structures on the surfaces of grains. EDS scans and XRD analysis confirmed the formation of bimetallic alloys, which suggests that these materials have great potential for further use as anode materials for Solid Oxide Fuel Cells (SOFCs).

Ongoing research to develop advanced electrocatalysts for the oxygen evolution reaction (OER) is needed to address demand for efficient energy conversion and carbon‐free energy sources. In the OER process, acidic electrolytes have higher proton concentration and faster response than alkaline ones, but their harsh strongly acidic environment requires catalysts with greater corrosion and oxidation resistance. At present, iridium oxide (IrO2) with its strong stability and excellent catalytic performance is the catalyst of choice for the anode side of commercial PEM electrolysis cells. However, the scarcity and high cost of iridium (Ir) and the unsatisfactory activity of IrO2 hinder industrial scale application and the sustainable development of acidic OER catalytic technology. This highlights the importance of further research on acidic Ir‐based OER catalysts. In this review, recent advances in Ir‐based acidic OER electrocatalysts are summarized, including fundamental understanding of the acidic OER mechanism, recent insights into the stability of acidic OER catalysts, highly efficient Ir‐based electrocatalysts, and common strategies for optimizing Ir‐based catalysts. The future challenges and prospects of developing highly effective Ir‐based catalysts are also discussed. [ABSTRACT FROM AUTHOR]

There is considerable interest in sending a mission to Enceladus to sample its erupting materials, which are sourced from its ocean, a proposed habitable environment. However, we lack resolution between competing ascent and eruption models, which offer differing consequences and challenges for mission sampling and access strategies. We report a new Enceladus ascent and eruption model, "Cryo‐Erupt," where ascent from ocean to jet is driven by the exsolution and expansion of dissolved gases from ascending water within conduits. This mechanism shares many similarities with some forms of terrestrial activity, including explosive silicate volcanism, cold‐water geysers and "limnic" eruptions. This preliminary study suggests that this mode of ascent and eruption is viable and broadly consistent with a range of observations including the apparent co‐existence of point‐ (jet) and fissure‐ (curtain) sourced activity as well as strong contrasts in velocity and ice‐to‐vapor ratio between the plume and the jets feeding it. However, it requires the co‐existence of a sublimation plume as an additive component to the broader plume. The outcomes of the Cryo‐Erupt model differ in terms of conduit physical and chemical processes from previously proposed boiling interface eruption models, for example, predicting larger dynamic pressures and narrower conduits, which could present challenges for direct robotic access. Due to the lack of a static boiling interface or wall condensation, bulk composition is unlikely to change appreciably during ascent from the ocean‐conduit interface to the jet, potentially simplifying the interpretation of samples collected in space or on Enceladus' surface. Plain Language Summary: High‐speed jets from giant ice fissures on Saturn's moon Enceladus feed a large plume, which is of interest to scientists because it contains salts and organic compounds, which are evidence of a subsurface ocean that may possibly host life. However, it is unclear how the chemistry of the plume material (gas and grains) might be altered as this material moves from the ocean into space, and to what extent samples from the plume are representative of ocean composition. Previous models to predict this behavior mostly relied on boiling of water as the primary way that gas and droplets are ejected, but these models do not take into account all of the physics involved, and do not fully reproduce what Cassini observed at Enceladus. We propose a new model that instead invokes dissolved gas molecules expanding, similar to explosive volcanoes on Earth and essentially the same mechanism that causes cans of soda to explode upon opening if shaken. We predict that the erupting jets would largely preserve bulk ocean content and thus would be the best place to study ocean content, in contrast with the broader plume, which would have more water that has sublimated from the surface. Key Points: Recent studies on the ascent and eruption of Enceladus' plume have neglected the role of exsolution and expansion of dissolved volatilesVolatile‐driven direct ocean‐to‐jet liquid water ascent is generally consistent with observations if combined with a sublimation co‐plumeThis mode of ascent could preserve ocean bulk content in jets, leading to jet sampling strategies being preferred for future missions [ABSTRACT FROM AUTHOR]

Metal exsolution engineering has been regarded as a promising strategy for activating intrinsically inert perovskite oxide catalysts toward efficient oxygen evolution reaction. Traditional metal exsolution processes on perovskites are often achieved by using the reducing hydrogen gas; however, this is not effective for the relatively stable phase, such as Ruddlesden–Popper perovskite oxides. To address this issue, triphenylphosphine is proposed to be a reduction promotor for accelerating the reduction and migration of the target metal atoms, aiming to achieve the effective exsolution of metallic species from Ruddlesden–Popper‐type parent perovskites. Upon oxygen evolution reaction, these exsolved metallic aggregates are reconstructed into oxyhydroxides as the real active centers. After further modification by low‐percentage iridium oxide nanoclusters, the optimal catalyst delivered an overpotential as low as 305 mV for generating the density of 10 mA cm−2, outperforming these reported noble metal‐containing perovskite‐based alkaline oxygen evolution reaction electrocatalysts. This work provides a potential approach to activate catalytically inert oxides through promoting surface metal exsolution and explores a novel class of Ruddlesden–Popper‐type oxides for electrocatalytic applications. [ABSTRACT FROM AUTHOR]

In this review, we have assessed the possibility of metal–perovskite interfacial engineering to enhance the catalytic activity and selectivity in a range of heterogeneous catalytic reactions. We embarked on a literature screening of different perovskite material classes and reactions to show the versatility of the perovskite structures to induce the formation of such hetero-interfaces and the widespread nature of the phenomenon in catalytic research. There is almost no limitation on the chemical composition of the used perovskites and the nature of the catalyzed reaction, be it under reduction or oxidation conditions. We attempted to classify the perovskite materials, discuss the different strategies leading to the hetero-interfaces, and detail the synergistic action of the components of the respective interfaces. We also provide a critical assessment of the large body of data that is available in terms of a knowledge-based approach to the comparison of differently prepared interfaces with varying interfacial extent to gain a deeper understanding of the bi-functional operation of the interfaces and the urgent necessity to study and characterize such interfaces under realistic operation conditions. [ABSTRACT FROM AUTHOR]

In this work, we performed a preliminary investigation on the redox behaviour of Sr2FeMo0.6Ni0.4O6-δ (SFMN) double perovskite in H2-H2O and CH4-H2O redox cycles in order to explore the potential use of this oxide as an Oxygen Carrier (OC) in fuel-assisted Chemical Looping Water Splitting (CLWS) processes driven by concentrated solar energy. The results were compared with our previous findings on the Reverse Water Gas Shift Chemical Looping (RWGS-CL) reaction. The improvement in performance due to the bimetallic exsolution on the OC surface is observed. This OC exhibits interesting activity and stability over CH4-assisted CLWS cycling. Future investigations are planned to examine the structural transformations that might impact the redox behaviour of this material in water splitting processes.

Abstract Exsolution of metal nanoparticles (NPs) on perovskite oxides has been demonstrated as a reliable strategy for producing catalyst‐support systems. Conventional exsolution requires high temperatures for long periods of time, limiting the selection of support materials. Plasma direct exsolution is reported at room temperature and atmospheric pressure of Ni NPs from a model A‐site deficient perovskite oxide (La0.43Ca0.37Ni0.06Ti0.94O2.955). Plasma exsolution is carried out within minutes (up to 15 min) using a dielectric barrier discharge configuration both with He‐only gas as well as with He/H2 gas mixtures, yielding small NPs (

In this review, we have assessed the possibility of metal–perovskite interfacial engineering to enhance the catalytic activity and selectivity in a range of heterogeneous catalytic reactions. We embarked on a literature screening of different perovskite material classes and reactions to show the versatility of the perovskite structures to induce the formation of such hetero-interfaces and the widespread nature of the phenomenon in catalytic research. There is almost no limitation on the chemical composition of the used perovskites and the nature of the catalyzed reaction, be it under reduction or oxidation conditions. We attempted to classify the perovskite materials, discuss the different strategies leading to the hetero-interfaces, and detail the synergistic action of the components of the respective interfaces. We also provide a critical assessment of the large body of data that is available in terms of a knowledge-based approach to the comparison of differently prepared interfaces with varying interfacial extent to gain a deeper understanding of the bi-functional operation of the interfaces and the urgent necessity to study and characterize such interfaces under realistic operation conditions.

Abstract Single silicate crystals hosting tiny magnetic inclusions are remarkable targets to study the paleointensities of the Earth and extraterrestrial samples. Since the pioneering work done in late 1990s, paleointensity studies using various silicate minerals such as feldspar, quartz, zircon, pyroxene, and olivine with magnetic inclusions trapped during grain growth or exsolved from the host phase have been reported. It has been shown that some single crystals have the ability to record paleomagnetic information as reliable or more reliable than the whole rock, by direct comparison of the obtained paleointensity estimate from single crystal and the whole-rock sample or the magnetic observatory data. Various rock-magnetic studies also support the fidelity of these crystals. Here, we provide a brief review of the rock-magnetic characteristics of the single crystals, the mineralogical background of the hosting silicates, and experimental procedures developed to obtain reliable data from magnetically weak samples with distinctive rock-magnetic features. We also overview the studies on paleointensity and related topics on various terrestrial and extraterrestrial samples published mainly after the comprehensive reviews in late 2000s. The present review covers the advantages as well as the limitations and caveats of paleointensity studies using single crystal samples and will help readers who wish to utilize this technique in their research. Graphical Abstract

Hydrogen production from methane with CO2 utilization over exsolution derived NiCu/CeO2 catalysts was studied. To form highly dispersed supported bimetallic NiCu particles the Ce0.75(NiCu)0.25O1.75 catalyst precursors (Cu/Ni molar ratio = 0; 0.004; 0.04; 0.25) were prepared by polymerizable complex method with the following reduction at 800 °C. A comparative study of the genesis, textural, structural and morphological properties of materials has been carried out by ex situ and in situ methods. It was shown that Ce0.75(NiCu)0.25O1.75 samples were fluorite-like ceria-based solid solutions with a mesoporous texture. Copper promotion has a positive effect on self-activation and hydrogen yield by improving the reducibility of the catalyst, lowering the exsolution temperature of the Ni2+ cations, and maintaining the concentration of oxygen vacancies. The catalyst of optimal composition NiCu/CeO2 (9.4 wt. % Ni, 0.4 wt. % Cu) formed from Ce0.75(NiCu)0.25O1.75 with Cu/Ni = 0.04 is resistant to coking and provides high hydrogen yield (82%) and CO2 utilization (78%) in steam/CO2 reforming of methane at 850 °C. [ABSTRACT FROM AUTHOR]

Copyright of Uranium Geology is the property of Uranium Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Single silicate crystals hosting tiny magnetic inclusions are remarkable targets to study the paleointensities of the Earth and extraterrestrial samples. Since the pioneering work done in late 1990s, paleointensity studies using various silicate minerals such as feldspar, quartz, zircon, pyroxene, and olivine with magnetic inclusions trapped during grain growth or exsolved from the host phase have been reported. It has been shown that some single crystals have the ability to record paleomagnetic information as reliable or more reliable than the whole rock, by direct comparison of the obtained paleointensity estimate from single crystal and the whole-rock sample or the magnetic observatory data. Various rock-magnetic studies also support the fidelity of these crystals. Here, we provide a brief review of the rock-magnetic characteristics of the single crystals, the mineralogical background of the hosting silicates, and experimental procedures developed to obtain reliable data from magnetically weak samples with distinctive rock-magnetic features. We also overview the studies on paleointensity and related topics on various terrestrial and extraterrestrial samples published mainly after the comprehensive reviews in late 2000s. The present review covers the advantages as well as the limitations and caveats of paleointensity studies using single crystal samples and will help readers who wish to utilize this technique in their research. [ABSTRACT FROM AUTHOR]

BaZr0.1Ce0.7Y0.2O3 (BZCY) perovskite with in‐situ exsolved metallic Cu catalyst acted as a catalyst for methanol steam reforming (MSR) for the first time. After reduction at 550 °C for 3 hours, fine and uniform metallic Cu nanoparticles were exsolved from the perovskite lattice with more active sites and oxygen vacancies on the surface. The reduced Ba0.9Zr0.1Ce0.7Y0.1Cu0.1O3 (BZCYCu) displayed a stable conversion of methanol above 99.9 % at 500 °C within 120 hours, with a negligible amount of CO in the outlet gas and no carbon species was detected on the surface of catalyst. The BZCYCu gained 7.4 % of their weight at 500 °C during the water vapor adsorption stage in temperature programmed water absorption experiment, which showed a considerable water adsorption capacity. Such a hygroscopicity could promote the catalytic methanol steam reforming and CO elimination. And metallic Cu has also been widely applied for the methanol steam reforming reaction due to their high activity and carbon resistance. The synergy of metallic Cu nanoparticles and perovskite substrate with more oxygen vacancies and well hydroscopicity improved the structural stability and ensured the catalytic activity of RBZCYCu catalysts. [ABSTRACT FROM AUTHOR]

The helium (He) contents of the Weiyuan and Anyue gas fields in the Sichuan Basin (China) differ significantly despite their similar helium‐nitrogen (N2) coupling characteristics, that is, the positive correlation between the N2 and He contents, and the negative correlation between the nitrogen/helium (N2/He) ratio and depth. To determine the factors influencing the differential enrichment of He resources and He–N2 coupling in the Weiyuan and Anyue gas fields, this study analysed the compositions of natural gases within the study area and established a computational model for evaluating the dissolution and exsolution amount of He and N2 in the pore water. The results indicated that: the uplift of the basement granite was crucial for the exsolution and enrichment of dissolved helium, and it was also the main reason for He–N2 coupling. The differential uplift that occurred in the Leshan–Longnvsi palaeo‐uplift during the Himalayan period further promoted the differential enrichment of He resources, thus also impacting the N2/He ratio in the study area. The distinct quantities of N2 and He exsolution during the uplift directly affected the negative correlation between the N2/He ratio and the depth. Within the same depth range of the uplift, the average and variations of the N2/He ratio in the crust‐derived helium‐rich natural gas reservoir were inversely proportional to the in situ molar partial pressure of He. The uplift of the crystalline basement is an important mechanism that causes the enrichment of helium resources and the coupling of helium‐nitrogen in the crust‐derived helium‐rich natural gas reservoir, which is of great significance for understanding the variation of N2/He ratio and exploration of He resources. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Exsolution is one of the most successful functionalization techniques to improve the catalytic activity of electrodes in solid oxide fuel and electrolyzer cells (SOFC/SOEC). The objective of this technique is to produce the highest possible number of metallic nanoparticles on the surface of a host-oxide, without significantly altering its structure. In this work, we compare three similar SOFC electrodes: STF (SrTi 0.3 Fe 0.7 O 3), STFN (Sr 0.93 Ti 0.3 Fe 0.63 Ni 0.07 O 3), and STFNC (Sr 0.93 Ti 0.3 Fe 0.56 Ni 0.07 Co 0.07 O 3), revealing that there is a significant difference between Ni–Fe/Ni–Co–Fe nanoparticle formation in STFN/STFNC and pure Fe0 particle formation in STF, which is evidenced by the size and amount of produced nanoparticles, but also by their anchoring to the host-oxide. The terms exsolution and particle segregation will be used, respectively, to distinguish these phenomena. Next, we explore two different reduction methods and observe that the characteristics of exsolution do not only depend on temperature, atmosphere and reduction times, but also on the reduction path taken to reach such conditions. [Display omitted] • Exsolution differs from particle segregation in the NP distribution, density, size and anchorage. • The characteristics of exsolved NPs are influenced by the hydrogen reduction path. • In-situ absorption spectroscopy is used to determine the exsolution temperature threshold. [ABSTRACT FROM AUTHOR]

Definition: Perovskite-type oxides (ABO3) are a highly versatile class of materials. They are compositionally flexible, as their constituents can be chosen from a wide range of elements across the periodic table with a vast number of possible combinations. This flexibility enables the tuning of the materials' properties by doping the A- and/or B-sites of the base structure, facilitating the application-oriented design of materials. The ability to undergo exsolution under reductive conditions makes perovskite-type oxides particularly well-suited for catalytic applications. Exsolution is a process during which B-site elements migrate to the surface of the material where they form anchored and finely dispersed nanoparticles that are crucially important for obtaining a good catalytic performance, while the perovskite base provides a stable support. Recently, exsolution catalysts have been investigated as possible materials for CO2 utilization reactions like reverse water–gas shift reactions or methane dry reforming. [ABSTRACT FROM AUTHOR]

The reverse water-gas shift reaction (rWGS) is of particular interest as it is the first step to producing high-added-value products from carbon dioxide (CO2) and renewable hydrogen (H2), such as synthetic fuels or other chemical building blocks (e.g. methanol) through a modified Fischer-Tropsch process. However, side reactions and material deactivation issues, depending on the conditions used, still make it challenging. Efforts have been put into developing and improving scalable catalysts that can deliver high selectivity while at the same time being able to avoid deactivation through high temperature sintering and/or carbon deposition. Here we design a set of perovskite ferrites specifically tailored to the hydrogenation of CO2 via the reverse water-gas shift reaction. We tailor the oxygen vacancies, proven to play a major role in the process, by partially substituting the primary A-site element (Barium, Ba) with Praseodymium (Pr) and Samarium (Sm), and also dope the B-site with a small amount of Nickel (Ni). We also take advantage of the exsolution process and manage to produce highly selective Fe-Ni alloys that suppress the formation of any by-products, leading to up to 100% CO selectivity.

Highlights Fundamental mechanisms in terms of driving force, material design, and exsolution processes are outlined, and novel behaviors of socketing and shape-shifting throughout the interaction with the oxide support are discussed. This review examines the key control factors, encompassing external conditions and intrinsic properties that affect the surface exsolution of metallic nanoparticles. The extraordinary nature of exsolution particles and their effect on various applications are discussed, along with the latest strategies for improving exsolution behavior.

Perovskite-type oxides (ABO3) are a highly versatile class of materials. They are compositionally flexible, as their constituents can be chosen from a wide range of elements across the periodic table with a vast number of possible combinations. This flexibility enables the tuning of the materials’ properties by doping the A- and/or B-sites of the base structure, facilitating the application-oriented design of materials. The ability to undergo exsolution under reductive conditions makes perovskite-type oxides particularly well-suited for catalytic applications. Exsolution is a process during which B-site elements migrate to the surface of the material where they form anchored and finely dispersed nanoparticles that are crucially important for obtaining a good catalytic performance, while the perovskite base provides a stable support. Recently, exsolution catalysts have been investigated as possible materials for CO2 utilization reactions like reverse water–gas shift reactions or methane dry reforming.

High catalytic performances of metal-semiconductor heterostructures have gained significant attention in recent years. However, developing fast and low-cost synthesis of multiphase heterojunction catalysts has long been a challenge. Herein, three phases of Cu-CeO2-SrTiO3-δ heterojunction catalyst are successfully synthesized by combining with sol-gel and rapid plasma exsolution method. Using dielectric barrier discharge plasma (DBD), Cu nanoparticles are exsolved and uniformly distributed on the surface of CeO2-SrTiO3-δ. This unique multiphase heterojunction catalyst exhibits superior performance in photothermal reverse water gas shift (RWGS) reactions. The yield of CO from this catalyst is impressive at 11.32 mmol g−1 h−1, 9 times greater than pure SrTiO3, and the selectivity for CO is high (99.95%). The enhanced activity is primarily attributed to the synergistic effect resulting from the incorporation of three phases of Cu nanoparticles, CeO2, and SrTiO3-δ, as well as their interfaces. The increase in oxygen vacancy sites in CeO2 enhances the adsorption of CO2, whereas the doping and exsolution of Cu help to broaden the light absorption range. A significant role is played by the localized surface plasmon resonance (LSPR) effect of Cu nanoparticles in promoting the catalytic performance of RWGS. This study demonstrates a simple and efficient method for fabricating multiphase heterojunction catalysts, providing new strategies for photothermal CO2 reduction.

This work addresses the formation of ammonia (NH3) decomposition catalysts derived from perovskites ABO3 (A=La, Ca, Sr, and B=Fe, Co, Ni) precursors via operando synchrotron X‐ray diffraction experiments. During the reaction in NH3, the perovskite precursors are decomposed and the transition metals are reduced. Depending on their reduction properties, active metallic catalysts are formed in situ on La2O3 as support. The reduction behavior of the perovskites, formation of intermediate phases during activation, and catalytic performance was studied in detail. In addition, microstructure properties such as crystallite sizes and particle morphology were analyzed. Co‐/Ni‐based perovskites decomposed completely during activation to Co0/Ni0 supported on La2O3 while Fe‐based perovskites were fully stable but inactive in catalysis. This difference is due to varying electronic properties of the transition metals, e. g. decreasing electronegativity from Ni to Fe. With decreasing reducibility, the intermediate phases during activation formed more distinct. La3+ was partially substituted by Ca2+/Sr2+ in LaCoO3 to test for advantageous effects in NH3 decomposition. The best performance was observed using the precatalyst La0.8Sr0.2CoO3 with a conversion of 86 % (100 % NH3, 15000 mL g−1 h−1) at 550 °C. [ABSTRACT FROM AUTHOR]

Protonic ceramic fuel cells (PCFCs) are promising eco‐energy electrochemical energy conversion systems that can efficiently operate in intermediate (500–700 °C) to low (500 °C) temperature ranges. In this review the most recent advances in materials research for the ceramic components of PCFCs (i.e., electrolyte, cathode, and anode) and their interface engineering are introduced. Recent approaches to improve the protonic of conductivity, and activity and stability of electrolyte and electrode materials are first presented. In addition, new attempts to stabilize/activate electrode/electrolyte interfaces and electrode surfaces are also discussed. Details of the theoretical background behind the electron and ion transfer processes at electrodes are also discussed. Finally, the challenges and perspectives of PCFC development are suggested from the point of view of materials engineering. [ABSTRACT FROM AUTHOR]

Given that the attempts to head toward a hydrogen economy are gathering pace, the dry reforming of methane (DRM) to produce hydrogen-rich syngas is a reaction that is worthy of investigation. Nickel-based catalysts have been extensively examined as a cost-effective solution for DRM, though they suffer from fast deactivation caused by coke accumulation. However, a number of published studies report high catalytic performance in terms of both activity and stability for La–Ni-based perovskite-derived catalysts used in DRM in comparison to other corresponding materials. In the work presented herein, a thorough analysis regarding the application of La–Ni-based perovskite catalysts for DRM is carried out. LaNiO3 is known for its anti-coking ability owing to the strong interaction between CO2 and La2O3. A further modification to improve the catalytic performance can be achieved by the partial or complete substitution of A or/and B sites of the perovskite catalysts. The latest developments with respect to this topic are also discussed in this manuscript. Even though the low surface area of perovskite catalysts has always been an obstacle for their commercialization, new supported and porous perovskite materials have recently emerged to address, at least partly, the challenge. Finally, conclusions and future outlooks for developing novel perovskite catalysts that may potentially pioneer new technology are included. [ABSTRACT FROM AUTHOR]

Apatite is an important petrogenetic indicator in extraterrestrial materials. Here, we report the mineralogical features of apatite and associated phases in three brachinites Northwest Africa (NWA) 4969, NWA 10637, and NWA 11756. Two types of apatite are observed: intergranular apatite and apatite inclusion within chromite and silicate minerals. The intergranular chlorapatite is enclosed by or penetrated by irregular porous merrillite, indicating chlorapatite replacement by merrillite. The intergranular chlorapatite is closely associated with a fine-grained pyroxene-troilite intergrowth along olivine grain boundaries, which is a sulfidization product of olivine. High-Ca pyroxene is observed as a constituent phase in the intergrowth for the first time. The apatite inclusions are either monomineralic or closely associated with subhedral-euhedral pore-free merrillite. In NWA 4969, the apatite inclusions show a large compositional variation from chlorapatite to fluorapatite and are systematically more F-rich than intergranular apatite; while the apatite inclusions in NWA 10637 and NWA 11756 are chlorapatite. Most of the two apatite types in brachinites contain oriented tiny or acicular chromite grains, suggesting the exsolution of chromite from apatite. We propose that apatite replacement by merrillite, formation of pyroxene-troilite intergrowth, and exsolution of chromite in apatite were caused by a shock-induced, transient heating event (~930–1000 °C) on the brachinite parent body. This heating event resulted in halogen devolatilization during replacement of the intergranular apatite by merrillite, which probably disturbed the Mn-Cr isotopic system in brachinites as well. We also propose that the apatite inclusions could be a residual precursor material of the brachinites. [ABSTRACT FROM AUTHOR]

Currently, catalyst design and development has drawn much attention as results of its strategic importance in the area of energy applications particular those involving biomass conversion. This work tailored exsolution of metal catalysts through the use of ceria for enhanced structural and catalytic behaviour in steam reforming of glycerol. Aside the understanding that defects due to A-site deficiency facilitates formation of vacant sites and exsolution of metal catalysts on the B-site of perovskite systems, this work has exemplified that metals such as ceria significantly influences the exsolution and general morphological surface architecture and catalytic behaviour. The exsolved nickel catalysts anchored and socketed on a titanate support and the ceria's basic surface properties and oxygen storage-release behaviour has modified the perovskite surface chemistry and enhanced catalytic behaviour particularly deactivation due to carbon deposition and reusability. Other exsolvable dopant metal species such as Fe and Co forms alloys with nickel on the surface and the synergy between the dopant metals in the alloy yielded better results. Furthermore, in one of the catalyst systems, the most commonly observed tolerable A-site deficiency and doping limit of 2% known for SrTiO 3 perovskite was overstretched by 0.5% (2.5%) thereby increasing the defect chemistry. The catalyst system with such formulation has shown a dramatic exsolution phenomenon and catalytic behaviour and robust suppression of coke deposition. CO selectivity >60% and H 2 selectivity >40% was recorded with all the catalyst systems. The catalysts used in this work are useful for applications in energy and production of value added chemicals. • Ceria enhances and mediates exsolution of nano metal catalysts. • Exsolved nono metals forms alloys with improved structural and surface chemistry. • High stability, reusability and great suppression of carbon deposition. • Overstretching of doping ratio by 0.5% enhanced defect chemistry and exsolution. [ABSTRACT FROM AUTHOR]

The in situ exsolution technique of nanoparticles has brought new opportunities for the utilization of perovskite‐based catalysts in solid oxide cells. However, the lack of control over the structural evolution of host perovskites during the promotion of exsolution has restricted the architectural exploitation of exsolution‐facilitated perovskites. In this study, we strategically broke the long‐standing trade‐off phenomenon between promoted exsolution and suppressed phase transition via B‐site supplement, thus broadening the scope of exsolution‐facilitated perovskite materials. Using carbon dioxide electrolysis as an illustrative case study, we demonstrate that the catalytic activity and stability of perovskites with exsolved nanoparticles (P‐eNs) can be selectively enhanced by regulating the explicit phase of host perovskites, accentuating the critical role of the architectures of perovskite scaffold in catalytic reactions occurring on P‐eNs. The concept demonstrated could potentially pave the way for designing the advanced exsolution‐facilitated P‐eNs materials and unveiling a wide range of catalytic chemistry taking place on P‐eNs. [ABSTRACT FROM AUTHOR]

As a low‐cost alternative to noble metals, Cu plays an important role in industrial catalysis, such as water‐gas shift reaction, methanol or ethanol oxidation, hydrogenation of oils, CO oxidation, among many others. An important step in optimizing Cu catalyst performance is control of nanoparticles size, distribution, and the interface with the support. While proton conducting perovskites can enhance the metal catalytic activity when acting as the support, there has been limited investigation of in situ growth of Cu metal nanoparticles from the proton conductors and its catalytic performance. Here, Cu nanoparticles are tracked exsolved from an A‐site‐deficient proton‐conducting barium cerate‐zirconate using scanning electron microscopy, revealing a continuous phase change during exsolution as a function of reduction temperature. Combined with the phase diagram and cell parameter change during reduction, a new exsolution mechanism is proposed for the first time which provides insight into tailoring metal particles interfaces at proton conducting oxide surfaces. Furthermore, the catalytic behavior in the CO oxidation reaction is explored and, it is observed that these new nanostructures can rival state of the art catalysts over long term operation. [ABSTRACT FROM AUTHOR]

A La0.9Ce0.1Mn0.8Ni0.1Cu0.1O3 (LCMNCu) perovskite nanomaterial with in situ-exsolved metallic nanoparticles (Re-LCMNCu) was fabricated successfully and acted as a catalyst for methanol steam reforming. Due to the fine and uniform NiCu alloy nanoparticles (∼35 nm) exsolved from the ceramic substrate, Re-LCMNCu displayed a stable conversion of methanol above 99% at 350 °C and maintained a hydrogen production rate of 285 mmol h–1 gcat–1 for 60 h, with a negligible amount of CO in the outlet gas. The NiCu alloy played an important role in catalytic activity, and the optimal prereduction treatment condition for catalyst activation was determined to be 6 h. Upon further examination, the NiCu alloy partially embedded into the substrate ensured high catalytic performance and the synergy between the NiCu alloy, CeO2 promoter, and perovskite substrate with more oxygen vacancies improved the catalytic activity of Re-LCMNCu catalysts. [ABSTRACT FROM AUTHOR]

Elemental vacancies are proposed as an effective approach to tuning the electronic structure of catalysts that are critical for energy conversion. However, for reactions such as the sluggish oxygen evolution reaction, the excess of oxygen vacancies (VO) is inevitable and detrimental to catalysts' electrochemical stability and activities, e.g., in the most active RuO2. While significant work is carried out to hinder the formation of VO, the development of a fast and efficient strategy is limited. Herein, a protection SrO layer produced successfully at the surface of RuO2 with the in situ exsolution method with perovskite SrRuO3 as the precatalyst, which could significantly hinder the generation of VO. Benefited from the suppression of VO, the surface‐modified RuO2 requires a low overpotential of 290 mV at 100 mA cm−2, accompanied by remarkably high electrochemical stability (100 h) and Faraday efficiency (≈100%). Theoretical investigation reveals that the formation energy of VO in RuO2 is almost doubled in the exsolved RuO2 phase as a result of the weakened RuO bond covalency. This work not only provides insight into the structural evolution of perovskite oxide catalysts but also demonstrates the feasibility of controlling vacancy formation via in situ exsolution. [ABSTRACT FROM AUTHOR]

Solid solutions Nd2−xSrxNiO4±δ (x = 0, 0.5, 1, 1.2, 1.4) with a K2NiF4 structure can be obtained from freeze-dried precursors. The end members of this series can be obtained at T ≥ 1000 °C only, while complex oxides with x = 1; 1.5 are formed at T ≥ 700 °C. Thermal analysis revealed the two stages of Nd2−xSrxNiO4±δ thermal reduction in a 10%H2/Ar gas mixture that was completed at 900 °C. For x < 0.2, the reduction products demonstrated an exsolution-like morphology with Ni nanoparticles allocated at the surface of oxide grains. As-obtained nanocomposites with x = 0 and x > 1 revealed the outstanding catalytic activity and selectivity in the dry reforming of the methane (DRM) reaction at 800 °C with CH4 conversion close to the thermodynamic values. The appearance of two different maxima of the catalytic properties of Ni/(Nd2O3,SrCO3) nanocomposites could be affiliated with the domination of the positive contributions of Nd2O3 and SrCO3, respectively. [ABSTRACT FROM AUTHOR]

Solid oxide electrolysis cell (SOEC) is a promising technology for CO2 conversion and renewable energy storage with high efficiency. It is highly desirable to develop catalytically active cathodes for CO2 electrolysis. Herein, cathode materials with different structural stabilities are designed by Nb substitution on La0.5Sr0.5Fe0.8Co0.2O3-δ (LSFC82) to obtain La0.5Sr0.5Fe0.7Co0.2Nb0.1O3-δ (LSFCN721) and La0.5Sr0.5Fe0.8Co0.1Nb0.1O3-δ (LSFCN811), respectively. LSFC82-Sm0.2Ce0.8O2-δ (SDC) cathode with inferior structural stability (ability to maintain the structure) shows desirable CO2 electrolysis performance with the generated current density of 1.80 A cm−2 at 1.6 V and stable performance during 110 h operation at 1.2 V and 800 °C. However, LSFC82 particles are collapsed into pieces after stability test with the generation of Co nanoparticles simultaneously. The frameworks of LSFCN721 and LSFCN811 particles maintain well because of the high-valent niobium, but Co exsolution, oxygen vacancy content and the corresponding CO2 electrolysis performance are restricted. This work confirms that Co nanoparticles can be exsolved from LSFC82-SDC cathode during CO2 electrolysis, providing references for constructing metallic nanoparticles decorated-perovskite cathodes for SOECs.

A Mn0.2Zr0.8O2−δ mixed oxide catalyst was synthesized via the co-precipitation method and studied in a CO oxidation reaction after different redox pretreatments. The surface and structural properties of the catalyst were studied before and after the pretreatment using XRD, XANES, XPS, and TEM techniques. Operando XRD was used to monitor the changes in the crystal structure under pretreatment and reaction conditions. The catalytic properties were found to depend on the activation procedure: reducing the CO atmosphere at 400–600 °C and the reaction mixture (O2 excess) or oxidative O2 atmosphere at 250–400 °C. A maximum catalytic effect characterized by decreasing T50 from 193 to 171 °C was observed after a reduction at 400 °C and further oxidation in the CO/O2 reaction mixture was observed at 250 °C. Operando XRD showed a reversible reduction-oxidation of Mn cations in the volume of Mn0.2Zr0.8O2−δ solid solution. XPS and TEM detected the segregation of manganese cations on the surface of the mixed oxide. TEM showed that Mn-rich regions have a structure of MnO2. The pretreatment caused the partial decomposition of the Mn0.2Zr0.8O2−δ solid solution and the formation of surface Mn-rich areas that are active in catalytic CO oxidation. In this work it was shown that the introduction of oxidation-reduction pretreatment cycles leads to an increase in catalytic activity due to changes in the origin of active states. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 into valuable fuels and chemicals has become a contemporary research area, where the heterogeneous catalyst plays a critical role. Metal nanoparticles supported on oxides performing as active sites of electrochemical reactions have been the focus of intensive investigation. Here, we review the CO2 reduction with active materials prepared by exsolution. The fundamental of exsolution was summarized in terms of mechanism and models, materials, and driven forces. The advances in the exsolved materials used in hightemperature CO2 electrolysis were catalogued into tailored interfaces, synergistic effects on alloy particles, phase transition, reversibility and electrochemical switching. [ABSTRACT FROM AUTHOR]

Oxidative coupling of methane (OCM) can be performed electrocatalytically by utilizing solid oxide cells, which provide a readily controlled oxygen supply through dense electrolytes. La0.7Sr0.2Ni0.2Fe0.8O3 (LSNF) perovskite is an effective anode for OCM. Its surface characteristics and electrocatalytic activity can be improved by reduction and the resultant exsolution of bimetallic NiFe nanoparticles from its bulk. X‐ray diffraction (XRD) and environmental transmission electron microscopy proved that the evolution of hetero‐phases under reducing environment resulted in bimetallic NiFe nanoparticles being formed on the surface. A 36 % improvement in C2+ hydrocarbon production rate was achieved due to the reduction of LSNF with the exsolved NiFe nanoparticles. Co‐feeding of H2O enhanced selective conversion of CH4 resulting in the production rate of C2+ hydrocarbons being increased by 56 %. Analysis of impedance spectra and in‐situ DRIFTS under a CH4+H2O atmosphere provided an understanding for the enhancement on the electrocatalytic OCM. [ABSTRACT FROM AUTHOR]

Hydrogen production from biogas over alumina-supported Ce1−xNixO2−x catalysts was studied in a temperature range of 600–850 °C with an initial gas composition of CH4/CO2/H2O of 1/0.8/0.4. To achieve a high and stable hydrogen yield, highly dispersed Ni catalysts were prepared through the exsolution approach. A solid solution of Ce1−xNixO2−x was firstly formed on the surface of Al2O3 and then activated in H2/Ar at 800 °C. The genesis and properties of the Ce1−xNixO2−x/Al2O3 catalysts were established using X-ray fluorescence analysis, thermal analysis, N2 adsorption, ex situ and in situ X-ray diffraction, Raman spectroscopy, electron microscopy, EDX analysis, and temperature-programmed hydrogen reduction. The performance of Ce1−xNixO2−x/Al2O3 catalysts in biogas conversion was tuned by regulation of the dispersion and reducibility of the active component through variation of content (5–20 wt.%) and composition (x = 0.2, 0.5, 0.8) of Ce1−xNixO2−x as well as the mode of its loading (co-impregnation (CI), citrate sol–gel method (SG)). For the 20 wt.% Ce1−xNixO2−x/Al2O3 catalyst, the rate of the coke formation decreased by a factor of 10 as x increased from 0.2 to 0.8. The optimal catalyst composition (20 wt.% Ce0.2Ni0.8O1.8/80 wt.% Al2O3) and preparation mode (citrate sol–gel method) were determined. At 850 °C, the 20 wt.% Ce0.2Ni0.8O1.8/Al2O3-SG catalyst provides 100% hydrogen yield at full CH4 conversion and 85% CO2 utilization. [ABSTRACT FROM AUTHOR]

A large proportion of the critical elements resources Ge, Ga, and In are associated with sphalerite in Pb-Zn ore deposits. Germanium in sphalerite has been proposed to be structurally bound in the crystal lattice. Using a combination of microstructural, geochemical and nanoscale observations, we show that Ge can be hosted in sphalerite crystal structure as well as nanoparticles of briartite (Cu 2 (Zn,Fe)GeS 4). The structurally-bound Ge was preserved in undeformed sphalerite grains from the Saint-Salvy Pb-Zn vein deposit (France), whereas the briartite nanoparticles were observed in metamorphosed sphalerite from Arre. The briartite nanoparticles likely exsolved from sphalerite during the Pyrenean-Alpine metamorphism and deformation. The presence of nanoparticles may harden the sphalerite during crystal-plastic deformation and help to preserve the critical elements resources of Pb-Zn deposits during metamorphism. [ABSTRACT FROM AUTHOR]

Abstract The benefits of perovskite oxides include their low cost, customizable composition, ordered atomic structure, and extremely flexible electronic structure. They are the ideal substitute for precious metal catalysts in various electrocatalytic reactions. However, the initial activity of perovskite oxides is often quite limited, which is extremely related to their crystal structure and electronic structure. In this regard, component regulation is the simplest and most effective strategy to increase their stability and catalytic activity. In this review, we briefly outline the recent progress in the modulating component of perovskite oxides to enhance their catalytic properties. The outline was categorized according to the sites in the ABO3‐type perovskite structure, including A‐site, B‐site, and O‐site regulation. Finally, potential research directions aimed at modulating of perovskite oxide constituents are discussed.

Abstract Elemental vacancies are proposed as an effective approach to tuning the electronic structure of catalysts that are critical for energy conversion. However, for reactions such as the sluggish oxygen evolution reaction, the excess of oxygen vacancies (VO) is inevitable and detrimental to catalysts’ electrochemical stability and activities, e.g., in the most active RuO2. While significant work is carried out to hinder the formation of VO, the development of a fast and efficient strategy is limited. Herein, a protection SrO layer produced successfully at the surface of RuO2 with the in situ exsolution method with perovskite SrRuO3 as the precatalyst, which could significantly hinder the generation of VO. Benefited from the suppression of VO, the surface‐modified RuO2 requires a low overpotential of 290 mV at 100 mA cm−2, accompanied by remarkably high electrochemical stability (100 h) and Faraday efficiency (≈100%). Theoretical investigation reveals that the formation energy of VO in RuO2 is almost doubled in the exsolved RuO2 phase as a result of the weakened RuO bond covalency. This work not only provides insight into the structural evolution of perovskite oxide catalysts but also demonstrates the feasibility of controlling vacancy formation via in situ exsolution.

Exsolution, as an effective approach to constructing particle-decorated interfaces, is still challenging to yield interfacial films rather than isolated particles. Inspired by in vivo near-infrared laser photothermal therapy, using 3 mol% Y _2 O _3 stabilized tetragonal zirconia polycrystals (3Y-TZP) as host oxide matrix and iron-oxide (Fe _3 O _4 / γ -Fe _2 O _3 / α -Fe _2 O _3 ) materials as photothermal modulator and exsolution resource, femtosecond laser ultrafast exsolution approach is presented enabling to conquer this challenge. The key is to trigger photothermal annealing behavior via femtosecond laser ablation to initialize phase transition from monoclinic zirconia (m-ZrO _2 ) to tetragonal zirconia (t-ZrO _2 ) and induce t-ZrO _2 columnar crystal growth. Fe-ions rapidly segregate along grain boundaries and diffuse towards the outmost surface, and become ‘frozen’, highlighting the potential to use photothermal materials and ultrafast heating/quenching behaviors of femtosecond laser ablation for interfacial exsolution. Triggering interfacial iron-oxide coloring exsolution is composition and concentration dependent. Photothermal materials themselves and corresponding photothermal transition capacity play a crucial role, initializing at 2 wt%, 3 wt%, and 5 wt% for Fe _3 O _4 / γ -Fe _2 O _3 / α -Fe _2 O _3 doped 3Y-TZP samples. Due to different photothermal effects, exsolution states of ablated 5 wt% Fe _3 O _4 / γ -Fe _2 O _3 / α -Fe _2 O _3 -doped 3Y-TZP samples are totally different, with whole coverage, exhaustion (ablated away) and partial exsolution (rich in the grain boundaries in subsurface), respectively. Femtosecond laser ultrafast photothermal exsolution is uniquely featured by up to now the deepest microscale (10 μ m from 5 wt%-Fe _3 O _4 -3Y-TZP sample) Fe-elemental deficient layer for exsolution and the whole coverage of exsolved materials rather than the formation of isolated exsolved particles by other methods. It is believed that this novel exsolution method may pave a good way to modulate interfacial properties for extensive applications in the fields of biology, optics/photonics, energy, catalysis, environment, etc.