Search

Alloying has significantly upgraded the oxygen reduction reaction (ORR) of Pd-based catalysts through regulating the thermodynamics of oxygenated intermediates. However, the unsatisfactory activation ability of Pd-based alloys toward O 2 molecules limits further improvement of ORR kinetics. Herein, the precise synthesis of nanosheet assemblies of spin-polarized PdCu-Fe 3 O 4 in-plane heterostructures for drastically activating O 2 molecules and boosting ORR kinetics is reported. It is demonstrated that the deliberate-engineered in-plane heterostructures not only tailor the d-band center of Pd sites with weakened adsorption of oxygenated intermediates but also endow electrophilic Fe sites with strong ability to activate O 2 molecules, which make PdCu-Fe 3 O 4 in-plane heterostructures exhibit the highest ORR specific activity among the state-of-art Pd-based catalysts so far. In situ electrochemical spectroscopy and theoretical investigations reveal a tandem catalytic mechanism on PdCu-Fe 3 O 4 ─Fe sites that initially activate molecular O 2 and generate oxygenated intermediates being transferred to Pd sites to finish the subsequent proton-coupled electron transfer steps., (© 2024 Wiley‐VCH GmbH.)

The great potential of K 1/2 Bi 1/2 TiO 3 (KBT) for dielectric energy storage ceramics is impeded by its low dielectric breakdown strength, thereby limiting its utilization of high polarization. This study develops a novel composition, 0.83KBT-0.095Na 1/2 Bi 1/2 ZrO 3 -0.075 Bi 0.85 Nd 0.15 FeO 3 (KNBNTF) ceramics, demonstrating outstanding energy storage performance under high electric fields up to 425 kV cm -1 : a remarkable recoverable energy density of 7.03 J cm -3 , and a high efficiency of 86.0%. The analysis reveals that the superior dielectric breakdown resistance arises from effective mitigation of space charge accumulation at the interface, influenced by differential dielectric and conductance behaviors between grains and grain boundaries. Electric impedance spectra confirm the significant suppression of space charge accumulation in KNBNTF, attributable to the co-introduction of Na 1/2 Bi 1/2 ZrO 3 and Bi 0.85 Nd 0.15 FeO 3 . Phase-field simulations reveal the emergence of a trans-granular breakdown mode in KNBNTF resulting from the mitigated interfacial polarization, impeding breakdown propagation and increasing dielectric breakdown resistance. Furthermore, KNBNTF exhibits a complex local polarization and enhances the relaxor features, facilitating high field-induced polarization and establishing favorable conditions for exceptional energy storage performance. Therefore, the proposed strategy is a promising design pathway for tailoring dielectric ceramics in energy storage applications., (© 2024 Wiley‐VCH GmbH.)

Density functional theory (DFT) calculations demonstrate neighboring Pt atoms can enhance the metal activity of NiCoP for hydrogen evolution reaction (HER). However, it remains a great challenge to link Pt and NiCoP. Herein, we introduced curvature of bowl-like structure to construct Pt/NiCoP interface by adding a minimal 1 ‰-molar-ratio Pt. The as-prepared sample only requires an overpotential of 26.5 and 181.6 mV to accordingly achieve the current density of 10 and 500 mA cm -2 in 1 M KOH. The water dissociation energy barrier (E a ) has a ~43 % decrease compared with NiCoP counterpart. It also shows an ultrahigh stability with a small degradation rate of 10.6 μV h -1 at harsh conditions (500 mA cm -2 and 50 °C) after 3000 hrs. X-ray photoelectron spectroscopy (XPS), soft X-ray absorption spectroscopy (sXAS), and X-ray absorption fine structure (XAFS) verify the interface electron transfer lowers the valence state of Co/Ni and activates them. DFT calculations also confirm the catalytic transition step of NiCoP can change from Heyrovsky (2.71 eV) to Tafel step (0.51 eV) in the neighborhood of Pt, in accord with the result of the improved H ads at the interface disclosed by in situ electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) tests., (© 2024 Wiley-VCH GmbH.)

Parallel nanomaterials possess unique properties and show potential applications in industry. Whereas, vertically aligned 2D nanomaterials have plane orientations that are generally chaotic. Simultaneous control of their growth direction and spatial orientation for parallel nanosheets remains a big challenge. Here, a facile preparation of vertically aligned parallel nanosheet arrays of aluminum-cobalt oxide is reported via a collaborative dealloying and hydrothermal method. The parallel growth of nanosheets is attributed to the lattice-matching among the nanosheets, the buffer layer, and the substrate, which is verified by a careful transmission electron microscopy study. Furthermore, the aluminum-cobalt oxide nanosheets exhibit high-temperature ferromagnetism with a 919 K Curie temperature and a 5.22 emu g -1 saturation magnetization at 300 K, implying the potential applications in high-temperature ferromagnetic fields., (© 2023 Wiley-VCH GmbH.)

The emergence of superconductivity in doped insulators such as cuprates and pnictides coincides with their doping-driven insulator-metal transitions. Above the critical doping threshold, a metallic state sets in at high temperatures, while superconductivity sets in at low temperatures. An unanswered question is whether the formation of Cooper pairsin a well-established metal will inevitably transform the host material into a superconductor, as manifested by a resistance drop. Here, this question is addressed by investigating the electrical transport in nanoscale rings (full loops) and half loops manufactured from heavily boron-doped diamond. It is shown that in contrast to the diamond half-loops (DHLs) exhibiting a metal-superconductor transition, the diamond nanorings (DNRs) demonstrate a sharp resistance increase up to 430% and a giant negative "magnetoresistance" below the superconducting transition temperature of the starting material. The finding of the unconventional giant negative "magnetoresistance", as distinct from existing categories of magnetoresistance, that is, the conventional giant magnetoresistance in magnetic multilayers, the colossal magnetoresistance in perovskites, and the geometric magnetoresistance in semiconductor-metal hybrids, reveals the transformation of the DNRs from metals to bosonic semiconductors upon the formation of Cooper pairs. DNRs like these could be used to manipulate Cooper pairs in superconducting quantum devices., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

There remain significant challenges in developing fast-charging materials for lithium-ion batteries (LIBs) due to sluggish ion diffusion kinetics and unfavorable electrolyte mass transportation in battery electrodes. In this work, a mesoporous single-crystalline lithium titanate (MSC-LTO) microrod that can realize exceptional fast charge/discharge performance and excellent long-term stability in LIBs is reported. The MSC-LTO microrods are featured with a single-crystalline structure and interconnected pores inside the entire single-crystalline body. These features not only shorten the lithium-ion diffusion distance but also allow for the penetration of electrolytes into the single-crystalline interior during battery cycling. Hence, the MSC-LTO microrods exhibit unprecedentedly high rate capability, achieving a specific discharge capacity of ≈174 mAh g -1 at 10 C, which is very close to its theoretical capacity, and ≈169 mAh g -1 at 50 C. More importantly, the porous single-crystalline microrods greatly mitigate the structure degradation during a long-term cycling test, offering ≈92% of the initial capacity after 10 000 cycles at 20 C. This work presents a novel strategy to engineer porous single-crystalline materials and paves a new venue for developing fast-charging materials for LIBs., (© 2022 Wiley-VCH GmbH.)

Metallic MoS 2 (i.e., 1T-MoS 2 ) is considered as the most promising precious-metal-free electrocatalyst with outstanding hydrogen evolution reaction (HER) performance in acidic media comparable to Pt. However, sluggish kinematics of HER in alkaline media and its inability for the oxygen evolution reaction (OER), hamper its development as bifunctional catalysts. The instability of 1T-MoS 2 further impedes its applications for scaling up, calling an urgent need for simple synthesis to produce stable 1T-MoS 2 . In this work, the challenge of 1T-MoS 2 synthesis is first addressed using a direct one-step hydrothermal method by adopting ascorbic acid. 1T-MoS 2 with flower-like morphology is obtained, and transition metals (Ni, Co, Fe) are simultaneously doped into 1T-MoS 2 . Ni-1T-MoS 2 achieves an enhanced bifunctional catalytic activity for both HER and OER in alkaline media, where the key role of Ni doping as single atom is proved to be essential for boosting HER/OER activity. Finally, a Ni-1T-MoS 2 ||Ni-1T-MoS 2 electrolyzer is fabricated, reaching a current density of 10 mA cm -2 at an applied cell voltage of only 1.54 V for overall water splitting., (© 2022 Wiley-VCH GmbH.)

Catalytically active metals atomically dispersed on supports presents the ultimate atom utilization efficiency and cost-effective pathway for electrocatalyst design. Optimizing the coordination nature of metal atoms represents the advanced strategy for enhancing the catalytic activity and the selectivity of single-atom catalysts (SACs). Here, we designed a transition-metal based sulfide-Ni 3 S 2 with abundant exposed Ni vacancies created by the interaction between chloride ions and the functional groups on the surface of Ni3S2 for the anchoring of atomically dispersed Pt (Pt SA -Ni 3 S 2 ). The theoretical calculation reveals that unique Pt-Ni 3 S 2 support interaction increases the d orbital electron occupation at the Fermi level and leads to a shift-down of the d -band center, which energetically enhances H 2 O adsorption and provides the optimum H binding sites. Introducing Pt into Ni position in Ni 3 S 2 system can efficiently enhance electronic field distribution and construct a metallic-state feature on the Pt sites by the orbital hybridization between S-3p and Pt-5d for improved reaction kinetics. Finally, the fabricated Pt SA -Ni 3 S 2 SAC is supported by Ag nanowires network to construct a seamless conductive three-dimensional (3D) nanostructure (Pt SA -Ni 3 S 2 @Ag NWs), and the developed catalyst shows an extremely great mass activity of 7.6 A mg -1 with 27-time higher than the commercial Pt/C HER catalyst., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Black phosphorus nanobelts are fabricated with a one-step solid-liquid-solid reaction method under ambient pressure, where red phosphorus is used as the precursor instead of white phosphorus. The thickness of the as-fabricated nanobelts ranges from micrometers to tens of nanometers as studied by scanning electron microscopy. Energy dispersive X-ray spectroscopy and X-ray diffraction indicate that the nanobelts have the composition and the structure of black phosphorus, transmission electron microscopy reveals a typical layered structure stacked along the b-axis, and scanning transmission electron microscopy with energy dispersive X-ray spectroscopy analysis demonstrates the doping of bismuth into the black phosphorus structure. The nanobelt can be directly measured in scanning tunneling microscopy in ambient conditions., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A protocol to quantify the distribution of surface atoms of concave nanocatalysts according to their coordination number is proposed. The 3D surface of an Au@Pd concave nanocube is reconstructed and segmented. The crystallographic coordinates and low-coordinate surface atom densities of the concave facets are determined. The result shows that 32% of the surface atoms are low-coordinated, which may contribute to the high activity., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

As-produced single-walled carbon nanotubes (SWCNTs) tend to aggregate in bundles due to π-π interactions. Several approaches are nowadays available to debundle, at least partially, the nanotubes through surface modification by both covalent and noncovalent approaches. Herein, we explore different strategies to afford an efficient covalent functionalization of SWCNTs with cobaltabisdicarbollide anions. Aberration-corrected HRTEM analysis reveals the presence of metallacarboranes along the walls of the SWCNTs. This new family of materials presents an outstanding water dispersibility that facilitates its processability for potential applications., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carbon nanotubes (CNTs) have been proposed as one of the most promising nanomaterials to be used in biomedicine for their applications in drug/gene delivery as well as biomedical imaging. The present study developed radio-labeled iron oxide decorated multi-walled CNTs (MWNT) as dual magnetic resonance (MR) and single photon emission computed tomography (SPECT) imaging agents. Hybrids containing different amounts of iron oxide were synthesized by in situ generation. Physicochemical characterisations revealed the presence of superparamagnetic iron oxide nanoparticles (SPION) granted the magnetic properties of the hybrids. Further comprehensive examinations including high resolution transmission electron microscopy (HRTEM), fast Fourier transform simulations (FFT), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) assured the conformation of prepared SPION as γ-Fe 2 O 3 . High r 2 relaxivities were obtained in both phantom and in vivo MRI compared to the clinically approved SPION Endorem ® . The hybrids were successfully radio-labeled with technetium-99m through a functionalized bisphosphonate and enabled SPECT/CT imaging and γ-scintigraphy to quantitatively analyze the biodistribution in mice. No abnormality was found by histological examination and the presence of SPION and MWNT were identified by Perls stain and Neutral Red stain, respectively. TEM images of liver and spleen tissues showed the co-localization of SPION and MWNT within the same intracellular vesicles, indicating the in vivo stability of the hybrids after intravenous injection. The results demonstrated the capability of the present SPION-MWNT hybrids as dual MRI and SPECT contrast agents for in vivo use.

In this work, we demonstrate the successful incorporation of pure fullerene from solution into two-dimensional layered aluminosilicate minerals. Pure fullerenes are insoluble in water and neutral in terms of charge, hence they cannot be introduced into the clay galleries by ion exchange or intercalation from water solution. To overcome this bottleneck, we organically modified the clay with quaternary amines by using well-established reactions in clay science in order to expand the interlayer space and render the galleries organophilic. During the reaction with the fullerene solution, the organic solvent could enter into the clay galleries, thus transferring along the fullerene molecules. Furthermore, we demonstrate that the surfactant molecules, can be selectively removed by either simple ion-exchange reaction (e.g., interaction with Al(NO3)3 solution to replace the surfactant molecules with Al(3+) ions) or thermal treatment (heating at 350 °C) to obtain novel fullerene-pillared clay structures exhibiting enhanced surface area. The synthesized hybrid materials were characterized in detail by a combination of experimental techniques including powder X-ray diffraction, transmission electron microscopy, X-ray photoemission, and UV/Vis spectroscopy as well as thermal analysis and nitrogen adsorption-desorption measurements. The reported fullerene-pillared clay structures constitute a new hybrid system with very promising potential for the use in areas such as gas storage and/or gas separation due to their high surface area., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule-based materials can combine physical and chemical properties associated with molecular-scale building blocks, their successful integration into real devices depends primarily on higher-order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced-dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is built up by means of a modified Langmuir-Blodgett technique, where the PBA is synthesized from precursors in a self-limited reaction on a clay mineral surface. The focus of this work is understanding the magnetic properties of the PBAs in different periodic, low-dimensional arrangements, and the influence of the "on surface" synthesis on the final properties and dimensionality of the system., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)