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Highly integrated energy systems are on the rise due to increasing global demand. To capture the underlying physics of such interdisciplinary systems, we need a modern framework that unifies all forms of energy. Here, we apply modified Lagrangian mechanics to the description of multi-energy systems. Based on the minimum entropy production principle, we revisit fluid mechanics in the presence of both mechanical and thermal dissipations and propose using exergy flow as the unifying Lagrangian across different forms of energy. We illustrate our theoretical framework by modeling a one-dimensional system with coupled electricity and heat. We map the exergy loss rate in real space and obtain the total exergy changes. Under steady-state conditions, our theory agrees with the traditional formula but incorporates more physical considerations such as viscous dissipation. The integral form of our theory also allows us to go beyond steady-state calculations and visualize the local, time-dependent exergy flow density everywhere in the system. Expandable to a wide range of applications, our theoretical framework provides the basis for developing versatile models in integrated energy systems. [ABSTRACT FROM AUTHOR]

The interfaces between heavy metals and antiferromagnetic materials have garnered significant attention due to their interesting physical properties. La0.35Sr0.65MnO3 (LSMO), as a typical manganite, exhibits an antiferromagnetic ground state that can be controlled through epitaxial strain and interfacial spin–orbit coupling. In this work, we reported the diverse magnetoresistance, influenced by the interfacial magnetic state, in Pt (3 nm)/LSMO (6–20 nm) heterostructures. The strong spin–orbit coupling of Pt and Dzyaloshinskii–Moriya interaction alter the spin structure and enhance the electron scattering at the Pt/LSMO interface, resulting in positive magnetoresistance. The interfacial angular-dependent magnetoresistance modulated by the interfacial magnetic states was also observed in the Pt/LSMO (20 nm) heterostructures. Our findings contribute to a broader understanding of interfacial properties between heavy metals and antiferromagnetic manganites. [ABSTRACT FROM AUTHOR]

BackgroundMetal-Support Interaction (MSI) modulates the activity, stability, and selectivity of catalysts by changing the morphology, composition, and electron density of metal particles. Such interactions in supported single-atom and cluster catalysts will be subjected to changes when the catalysts are treated at different temperatures and under different atmospheres.PurposeThis study aims to explore the effects of high temperature treatment on metal-support interactions of Pt/TiO2 and Pt/SiO2 catalysts with the coexistence of single atoms and clusters when heating and calcined in air at high temperature.MethodsThe structural evolutions of these two catalysts were investigated by a combination of high-resolution transmission electron microscopy (HRTEM), aberration-corrected high-angle annular dark-field transmission electron microscopy (AC-HAADF-STEM), synchrotron radiation technique X-ray absorption fine structure spectroscopy (XAFS), diffuse reflection Fourier transform infrared spectroscopy (DRIFT). XAFS characterization was conducted at Beijing Synchrotron Radiation Facility (BSRF) 1W1B beamline station to obtain information about the valence state and coordination environment of Pt/TiO2 at different calcination temperatures to confirm that Pt mono-atoms were immobilized on the support by Covalent Metal-Support Interaction (CMSI).ResultsAfter calcination at 700 ℃, all Pt species are presented as Pt single atoms in Pt/TiO2, while they agglomerate into larger particles in Pt/SiO2. The reducibility of metal oxides determines the ability of the support for anchoring single atoms of Pt: single atoms of Pt in TiO2 can be stabilized via the CMSI, and thus facilitate the dispersion of Pt atoms. On the contrast, CMSI cannot be formed between Pt and SiO2, resulting in particle sintering at high temperatures.ConclusionsThe formation of CMSI effect between metals and supports can be used as a general method for the preparation of reducible oxide supported high-loading, thermally stable single-atom catalysts.

BackgroundMetal-oxide interface plays critical roles in promoting the catalytic activities of metal catalysts in a vast diversity of reactions. Maximizing this interfacial interaction so as to optimize the catalytic performance is an active subject of research that is worthy of intensive exploration.PurposeThis study aims to develop new Pt-group catalysts that are highly active towards cryogenic CO catalytic oxidation, and explore effective strategies to engineer metal-oxide (hydroxide) interfaces to weaken the adsorption of CO and to enhance the adsorption/activation of O2.MethodsSupported ultrasmall Pt nanoclusters (Ptnc-FeOx/SiO2) of (1.4±0.2) nm were synthesized using deposition-precipitation with urea (DPU). The catalytic performance towards CO oxidation was examined by using a fixed-bed U-shape flow quartz reactor. Extended X-ray absorption fine structure (EXAFS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy-dispersive X-ray spectroscopy (EDX) techniques were combined to study the Ptnc-FeOx interfacial interaction.ResultsThe Ptnc-FeOx/SiO2 catalyst shows superior catalytic performance than Pt/SiO2 towards the CO oxidation reaction. Kinetics tests show that both the apparent activation energy and turnover frequency of Ptnc-FeOx/SiO2 are greatly enhanced as compared with Pt/SiO2 (19 kJ·mol-1 vs. 64 kJ·mol-1; 0.044 s-1 vs. 0.002 s-1 at 37 °C).ConclusionThe charge transfer from Fe to Pt results in the downshifted d-band center of Pt and reduces the CO adsorption strength, and hence, playing important roles in promoting the catalytic activity of Pt catalysts.

Strong metal‐support interactions characteristic of the encapsulation of metal particles by oxide overlayers have been widely observed on large metal nanoparticles, but scarcely occur on small nanoclusters (<2 nm) for which the metal‐support interactions remain elusive. Herein, we study the structural evolution of Pt nanoclusters (1.5 nm) supported on anatase TiO2 upon high‐temperature H2 reduction. The Pt nanoclusters start to partially evolve into a CsCl‐type PtTi intermetallic compound when the reduction temperature reaches 400 °C. Upon 700 °C reduction, the PtTi nanoparticles are exclusively formed and grow epitaxially along the TiO2 (101) crystal faces. The thermodynamics of the formation of PtTi via migration of reduced Ti atoms into Pt cluster is unraveled by theoretical calculations. The thermally stable PtTi intermetallic compound, with single‐atom Pt isolated by Ti, exhibits enhanced catalytic activity and promoted catalytic durability for CO oxidation. [ABSTRACT FROM AUTHOR]

Metal-oxide/hydroxide hybrid nanostructures provide an excellent platform to study the interfacial effects on tailoring the catalysis of metal catalysts. Herein, a hybrid nanostructure of Pt@Co(OH)2 supported on SiO2 was synthesized by incipient wetness impregnation of Co(OH)2 with the aid of H2O2 and successive urea-assisted deposition-precipitation of platinum nanoparticles. The Fenton-like reaction between Co2+ and H2O2 during the impregnation process facilitates the formation of active interfacial sites. This hybrid nanostructure exhibits much higher catalytic activity towards CO oxidation than Pt/SiO2 nanoparticles with a similar Pt loading and particle size. In situ diffuse reflectance infrared Fourier transform spectroscopy was used to track the CO adsorption processes and to identify the reaction intermediates during CO oxidation. It shows that the OH species at the Pt-OH-Co interfacial sites could readily react with CO adsorbed on neighboring Pt to yield CO2 by forming *COOH intermediates and oxygen vacancies. Under the CO + O2 oxidation conditions, O2 molecules are activated by the oxygen vacancy and react with the CO molecules adsorbed on Pt to generate CO2, via forming the highly active *OOH intermediates as observed by DRIFTS.