Motivating Inert Strontium Manganate with Iridium Dopants as Efficient Electrocatalysts for Oxygen Evolution in Acidic Electrolyte.

The search for high-performance and low-cost electrocatalysts in acid conditions still remains a challenging target. Herein, iridium (Ir) doped strontium manganate (named as Irx -SMO) is proposed as an efficient and durable low-iridium electrocatalyst for water oxidation in acidic media. The Ir0.1 -SMO with 75% less iridium in comparison to that of iridium dioxide (IrO2 ) exhibits excellent performance for oxygen evolution reaction (OER), which is even better than most of the iridium-based oxide electrocatalysts. The theoretical outcomes confirm the activation of the inert manganese sites in strontium manganate by the incorporation of iridium dopants. This work reveals the boosted effect of the iridium dopants on the OER activity of strontium manganate, providing a strategy to tune the activity of manganese-based perovskites in electrocatalysis.

Synergistic Effect Enables the Dual-Metal Doped Cobalt Telluride Particles as Potential Electrocatalysts for Oxygen Evolution in Alkaline Electrolyte.

Cobalt (Co)-based materials have been widely investigated as hopeful noble-metal-free alternatives for the oxygen evolution reaction (OER) in alkaline electrolytes, which is crucial for generating hydrogen by water electrolysis. Herein, cobalt-based telluride particles with good electronic conductivity as anodic electrocatalysts were prepared under vacuum by the solid-state strategy, which display remarkable activities toward the OER. Nickel (Ni) and iron (Fe) codoped cobalt telluride (NiFe-CoTe) exhibits an overpotential of 321 mV to achieve a current density of 10 mA cm-2 and a Tafel slope of 51.8 mV dec-1, outperforming the performances of CoTe, CoTe2, and IrO2. According to the DFT calculation, the adsorbed hydroxyl-assisted adsorbate evolution mechanism was proposed for the OER process of NiFe-CoTe, which reveals the synergetic effect toward OER induced by codoping of the Ni and Fe atoms. This work proposes a rational strategy to prepare cobalt-based tellurides as efficient OER catalysts in alkaline electrolytes, providing a new strategy to prepare and regulate metal-based tellurides for catalysis and beyond.

Modulating the oxygen evolution reaction activity of SrIrO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 catalysts using electric-field polarization.

The physical properties of epitaxially grown SrIrO3 thin films are sensitive to external influences. This provides a rare opportunity to study their physical properties as regulated by electric-field polarization of their substrates, thus affecting their oxygen evolution reaction activity. In this work, SrIrO3 films were epitaxially grown on (001)-oriented Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMNPT) single-crystal substrates by pulsed laser deposition. After applying an electric field to the PMNPT along the [001] direction, a lattice strain is induced by rotation of its ferroelectric domains, and this lattice strain is transferred to the interior of the SrIrO3 film through the epitaxial interface. This changes the surface resistivity of the SrIrO3 film and affects its electrocatalytic activity. Our findings suggest that substrate polarization is a feasible method for regulating the electrocatalytic performance of SrIrO3 thin films, and this provides new inspiration for the structural design of other composite catalysts.

Monoatomic Platinum-Embedded Hexagonal Close-Packed Nickel Anisotropic Superstructures as Highly Efficient Hydrogen Evolution Catalyst.

The rational design of platinum (Pt) based nanostructures with specific crystal structure plays a significant role in their diverse applications. Herein, the anisotropic superstructures (ASs) of monoatomic Pt-embedded hexagonal close-packed nickel (hcp Ni) nanosheets were successfully synthesized for efficient hydrogen evolution in which an unusual dissociation-diffusion-desorption mechanism played a crucial role. The overpotential for the Pt/Ni ASs to reach the specific current density (10 mA cm-2) is 28.0 mV, which is much lower than that of conventional Pt/C catalyst (71.0 mV). Moreover, at the overpotential of 100 mV, the mass activity of 30.2 A mgPt-1 for the Pt/Ni ASs is 1060% greater than that in conventional Pt/C catalyst (2.6 A mgPt-1). This work provides a new approach to synthesize highly anisotropic superstructures embedded with monoatomic noble metals to boost their hopeful applications in catalytic applications.

Morphology and Phase Controlled Construction of Pt-Ni Nanostructures for Efficient Electrocatalysis.

Highly open metallic nanoframes represent an emerging class of new nanostructures for advanced catalytic applications due to their fancy outline and largely increased accessible surface area. However, to date, the creation of bimetallic nanoframes with tunable structure remains a challenge. Herein, we develop a simple yet efficient chemical method that allows the preparation of highly composition segregated Pt-Ni nanocrystals with controllable shape and high yield. The selective use of dodecyltrimethylammonium chloride (DTAC) and control of oleylamine (OM)/oleic acid (OA) ratio are critical to the controllable creation of highly composition segregated Pt-Ni nanocrystals. While DTAC mediates the compositional anisotropic growth, the OM/OA ratio controls the shapes of the obtained highly composition segregated Pt-Ni nanocrystals. To the best of our knowledge, this is the first report on composition segregated tetrahexahedral Pt-Ni NCs. Importantly, by simply treating the highly composition segregated Pt-Ni nanocrystals with acetic acid overnight, those solid Pt-Ni nanocrystals can be readily transformed into highly open Pt-Ni nanoframes with hardly changed shape and size. The resulting highly open Pt-Ni nanoframes are high-performance electrocatalysts for both oxygen reduction reaction and alcohol oxidations, which are far better than those of commercial Pt/C catalyst. Our results reported herein suggest that enhanced catalysts can be developed by engineering the structure/composition of the nanocrystals.

Facile synthesis of ultrathin bimetallic PtSn wavy nanowires by nanoparticle attachment as enhanced hydrogenation catalysts.

Ultrathin wavy nanowires represent an emerging class of nanostructures that exhibit unique catalytic, magnetic, and electronic properties, but the controlled production of bimetallic wavy nanowires remains a significant challenge. Ultrathin bimetallic PtSn nanowires have been prepared with high yield and featuring a highly wavy structure. Owing to the ultrathin nature and unique electronic properties of these PtSn wavy nanowires, they exhibit improved catalytic performance for the hydrogenation of nitrobenzene, as well as for the hydrogenation of styrene. These results suggest a new strategy to prepare highly active catalysts through defect engineering and can significantly impact broad practical applications.

Laser-machined micro-supercapacitors: from microstructure engineering to smart integrated systems.

With the rapid development of portable and wearable electronic devices, there is an increasing demand for miniaturized and lightweight energy storage devices. Micro-supercapacitors (MSCs), as a kind of energy storage device with high power density, a fast charge/discharge rate, and a long service life, have attracted wide attention in the field of energy storage in recent years. The performance of MSCs is mainly related to the electrodes, so there is a need to explore more efficient methods to prepare electrodes for MSCs. The process is cumbersome and time-consuming using traditional fabrication methods, and the development of laser micro-nano technology provides an efficient, high-precision, low-cost, and convenient method for fabricating supercapacitor electrodes, which can achieve finer mask-less nanofabrication. This work reviews the basics of laser fabrication of MSCs, including the laser system, the structure of MSCs, and the performance evaluation of MSCs. The application of laser micro-nanofabrication technology to MSCs and the integration of MSCs are analyzed. Finally, the challenges and prospects for the development of laser micro-nano technology for manufacturing supercapacitors are summarized.

Graphene enhances the shape memory of poly (acrylamide-co-acrylic acid) grafted on graphene.

Acrylamide and acrylic acid are grafted on graphene by free-radical polymerization to produce a series of graphene-poly(acrylamide-co-acrylic acid) hybrid materials with different contents of graphene. The materials demonstrate shape memory effect and self-healing ability when the content of graphene is in the range of 10%-30% even though poly(acrylamide-co-acrylic acid) itself had poor shape memory ability. The permanent shape of the materials can be recovered well after 20 cycles of cut and self-healing. The result is attributed to the hard-soft design that can combine nonreversible "cross-link" by grafting copolymer on graphene and reversible "cross-link" utilizing the "zipper effect" of poly(acrylamide-co-acrylic acid) to form or dissociate the hydrogen-bond network stimulated by external heating.

Iron-Doped Monoclinic Strontium Iridate as a Highly Efficient Oxygen Evolution Electrocatalyst in Acidic Media.

Ir-based perovskite oxides are efficient electrocatalysts for anodic oxygen evolution. This work presents a systematic study of the doping effects of Fe on the OER activity of monoclinic SrIrO3 to reduce the consumption of Ir. The monoclinic structure of SrIrO3 was retained when the Fe/Ir ratio was less than 0.1/0.9. Upon further increases in the Fe/Ir ratio, the structure of SrIrO3 changed from a 6H to 3C phase. The SrFe0.1Ir0.9O3 had the highest activity among the investigated catalysts with the lowest overpotential of 238 mV at 10 mA cm-2 in 0.1 M HClO4 solution, which could be attributed to the oxygen vacancies induced by the Fe dopant and the IrOx formed upon the dissolution of Sr and Fe. The formation of oxygen vacancies and uncoordinated sites at the molecular level may be responsible for the improved performance. This work explored the effect of Fe dopants in boosting the OER activity of SrIrO3, thus providing a detailed reference to tune perovskite-based electrocatalyst by Fe for other applications.

Stretched three-dimensional white graphene with a tremendous lattice thermal conductivity increase rate.

Despite the increasing interest in the physical properties of the newly synthesized three-dimensional (3D) nano-architectured graphene, there are still few studies on the thermal transport properties of this family of materials. In the present work, heat transport of 3D h-BN and its mechanical response are systematically explored through first principles calculations. It is fascinating to find that the thermal conductivity of the 3D h-BN honeycomb structure could be significantly modulated by mechanical tension. Its lattice thermal conductivity perpendicular to the hole axis increases by 7.2 times at 6% critical strain, compared to only 0.67 times for that of the strained 3D graphene counterpart. The structure's thermal conductivity versus mechanical tension differs quantitatively and qualitatively from the monotonic downward trend of traditional bulk diamond or silicon under tension. This deviation from the classic behavior could be attributed to the modification of the phonon lifetimes, together with the competition between group velocities of low- and high-lying phonons under strain. Finally, the phonon vibrational modes contribution analysis indicates that the BN ribbon atoms contribute mainly at a lower frequency range. Our results provide important insights into potential employment of nano-architectured 3D white graphene for thermal management in relevant industrial applications.

Highly open rhombic dodecahedral PtCu nanoframes.

Herein, we report a facile strategy that allows one-pot preparation of highly open rhombic dodecahedral PtCu alloy nanoframes. Due to the highly open structures, the PtCu nanoframes exhibit enhanced catalytic performance in methanol electrooxidation, showing a new strategy to create highly active catalysts.

A General Method for Multimetallic Platinum Alloy Nanowires as Highly Active and Stable Oxygen Reduction Catalysts.

An unconventional class of high-performance Pt alloy multimetallic nanowires (NWs) is produced by a general method. The obtained PtNi NWs exhibit amazingly specific and mass oxygen reduction reaction (ORR) activities with improvement factors of 51.1 and 34.6 over commercial Pt/C catalysts, respectively, and are also stable in ORR conditions, making them among the most efficient electrocatalysts for ORR.

One-pot synthesis and functionalisation of Fe2O3@C-NH2 nanoparticles for imaging and therapy.

The authors have prepared amine-modified Fe2O3@C nanoparticles with diameter of 20 nm by decomposing perchlorinated pyrene/Fe(NO3)3 mixture in the presence of ammonia in solvothermal conditions at 180°C for 48 h by a one-step process. NH3 is not only a cocatalyst of Fe(NO3)3 for decomposition of perchlorinated pyrene, but also the source of surface functionalisation group. The effect of synthesis conditions on shape and size of nanoparticles and characterisation of their structure and functionalisation group are investigated in this research. The amino group in the surface of core-shell nanoparticles can be further functionalised with polyethylene glycol and folic acid to improve their solubility in aqueous solution and target cancer cells. The applications of functionalised core-shell nanoparticles in magnetic resonance imaging and cancer thermal therapy are also investigated in this research.