Engineering the surface structure, together with the incorporation of a second metal, is an effective strategy for boosting the catalytic activities of Pt-based catalysts toward various reactions. Here, we report a facile approach to the synthesis of Pt–Ag octahedral and tetrahedral nanocrystals covered by concave surfaces. The presence of the Ag(I) precursor not only facilitated the reduction of the Pt(IV) precursor but also led to the formation of concaved facets on the Pt–Ag nanocrystals. Besides, poly(vinylpyrrolidone) (PVP) was demonstrated to serve as a co-reductant, in addition to its role as a colloidal stabilizer. Using PVP with different molecular weights, we were able to tune the size of the Pt–Ag nanocrystals in the range of 9–25 and 14–32 nm for the octahedral and tetrahedral shapes, respectively. The Pt–Ag nanocrystals exhibited 4.6- and 2.0-fold enhancements in terms of specific and mass activities, respectively, toward methanol oxidation, when benchmarked against the commercial Pt/C catalyst. After 1000 cycles of the accelerated tests, the specific and mass activities of the Pt–Ag nanocrystals were still 3.6 and 1.6 times as high as those of the original commercial Pt/C.

Lithium (Li)-ion battery cathode materials are typically coated to improve cycling performance, using aqueous-based coating techniques that require filtering, drying, and even sintering of the final product. Here, spherical LiNi0.6Mn0.2Co0.2O2 particles were coated with nano-Al2O3 using the dry mechanofusion method. This method produced a durable, non-porous Al2O3 coating that is retained during slurry making. Mechanofusion coatings significantly improved Li-ion battery cathode cycling at high voltages, enabling high energy densities, while offering inexpensive, scalable, and environmentally friendly solvent-free synthesis. This opens up new possibilities, since, not being limited by synthesis chemistry, mechanofusion can in principle be used to apply any coating material.

Graphitic carbon nitride (g-C3N4) microspheres (CNMS) were fabricated via a solvothermal method by using dicyandiamide and cyanuric chloride as precursors. The morphology, band structure, and defects can be simultaneously regulated by merely adjusting the concentration of precursors. Structural characterization results indicate that all the prepared samples possess spherical morphology, while the band gap decreased as the precursor concentration increased from 8 mmol (CNMS-1) to 24 mmol (CNMS-3). Besides, ultraviolet photoelectron spectroscopy results suggested that the valence band of CNMS-2 (16 mmol) was much higher than that of CNMS-1 and CNMS-3. Additionally, organic elemental analysis, X-ray photoelectron spectroscopy, and electron paramagnetic resonance results unveil the formation of nitrogen defects on the surface of prepared samples. Besides, CNMS-2 exhibits an enhanced apparent reaction rate constant of RhB degradation than that of CNMS-1 and CNMS-3. The improved apparent reaction rate constant may be due to the lowered valence band as well as the formation of nitrogen defects. This work might guide the regulation of the morphology and band structure of g-C3N4-based materials prepared via the one-pot hydrothermal method.

Pressureless sintering is a simple and traditional processing method for producing dense ceramics by heating at a high temperature. The introduction of water vapor into this atmosphere can decrease the sintering temperature and accelerate grain growth. In this work, we report water vapor-assisted sintering of submicrometer titania (TiO2) powder. Dense TiO2 pellets with a relative density over 99% were obtained in 0.1 MPa of water vapor at a lower temperature than in air. The submicrometer particles (∼0.5 µm) grew to an average size of 181 µm after sintering at 1400 °C in water vapor, whereas the particle size obtained by sintering in air was 51 µm. Furthermore, we verified the incorporation of oxygen from water vapor into TiO2 by using isotopically labeled water (H218O). Water vapor-assisted sintering can potentially lead to the production of single crystal-like ceramics by a pressureless route and without any additives.

The effect of Cu addition varied from 0 to 4 mass% on the corrosion resistance and electrochemical response in Ni–Co–Cr–Mo alloys was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy, and Mott–Schottky analysis. Results indicate that the Ni–Co–Cr–Mo alloy with 2 mass% Cu exhibited the most superior corrosion resistance, and the presence of Cu greatly influenced the outer porous layer. The Ni–Co–Cr–Mo alloys’ corrosion resistance was not simply increasing with copper addition increasing from 0 to 4 mass%. The X-ray photoelectron spectroscopy etching analysis was also conducted to illustrate the fraction of Cu at various depths in the passive film, and the results reveal that a maximum limit on Cu content (appropriately 3.10 mass%) existed in the outermost surface in the present condition. Among the studied alloys, the Ni–Co–Cr–Mo–2%Cu alloy formed the thickest passive film with the lowest donor density.

An epitaxial NdFeAs(O,F) thin film of 90 nm thickness grown by molecular beam epitaxy on MgO single crystal with Tc = 44.2 K has been investigated regarding a possible vortex glass–liquid transition. The voltage–current characteristics show excellent scalability according to the vortex-glass model with a static critical exponent ν of around 1.35 and a temperature-dependent dynamic exponent z increasing from 7.8 to 9.0 for the investigated temperature range. The large and non-constant z values are discussed in the frame of 3D vortex glass, thermally activated flux motion, and inhomogeneity broadening.

Historically, batteries with lithium metal anodes have been a hazard, as the lithium becomes rough and eventually finely divided during cycling. The promise of higher energy density, however, continues to drive the search for novel approaches to manage this light and reactive material. Significant improvement has been achieved by designing new liquid-electrolyte compositions and interface barriers to stabilize the lithium in traditional batteries, but it is clear that solid-state batteries ensure a higher level of safety and perhaps higher energy density and lifetimes. The materials challenge then is to fabricate a cost-effective solid electrolyte that effectively maintains lithium as a dense uniform metal layer. This article describes the ideal cycling behavior of lithium and progress toward this goal of a solid electrolyte using glassy, ceramic, polymer, and composite electrolytes, as well as the challenges that continue to arise toward long-term, high-rate, and efficient cycling of lithium metal.

The flow of heat in materials is generally perceived to be a slow process and, therefore, pump-probe techniques originally developed for ultrafast time-resolved optical spectroscopy are not an obvious source of technologies for advances in thermal-property measurements. Nevertheless, over the past 18 years, the work of approximately 30 dedicated students and postdoctoral researchers at the University of Illinois at Urbana-Champaign has developed time-domain thermoreflectance (TDTR) into a nearly universal, high-throughput tool for measuring the thermal conductivity of materials and the thermal conductance of materials interfaces. This article illustrates the utility of TDTR and surveys current topics in the science of heat conduction in materials with recent examples drawn from high-thermal-conductivity crystals of cubic boron phosphide and boron arsenide, structure–property relationships for thermal conductivity of amorphous polymers, and thermal conductivity switching in liquid-crystal networks.

Solid-state batteries are considered the holy grail of next-generation battery technology, meeting the ever-increasing demand for energy storage that is affordable and safe, with high energy density and long cycle life. Materials and interfaces play a critical role for their eventual success and mass commercialization. This issue of MRS Bulletin focuses on the current state of the art of solid-state electrolytes and device architectures and provides a perspective into the various materials and interfacial challenges that limit its performance and stability.