Liquid-Phase Templateless Synthesis of Pt-on-Pd_0.85Bi_0.15 Nanowires and PtPdBi Porous Nanoparticles with Superior Electrocatalytic Activity

This article reports the synthesis of Pt-on-Pd_0.85Bi_0.15 nanowires (NWs) and PtPdBi porous nanoparticles (PNPs) by a facile, one-pot, wet-chemical, and templateless method in the presence of oleylamine (OAm) and NH₄Br. The relationship between the morphology and composition in the PtPdBi trimetallic system was systematically studied. Interestingly, it is verified that adding only 5% Bi will produce Pd NWs, which offers a novel approach to synthesize Pd NWs in the oil phase without any template. On the basis of the fact of synthesizing Pd_0.85Bi_0.15 NWs, Pt-on-Pd_0.85Bi_0.15 NWs with hetero-nanostructures were successfully synthesized by a one-step method. Furthermore, the number of Pt nanobranches for Pt-on-Pd_0.85Bi_0.15 NWs could be easily controlled via simply changing the synthetic parameters, which could tune the catalytic properties. PtPdBi PNPs were obtained by the acid pickling of PtPdBi₂ intermetallic compounds. Most importantly, a catalytic study indicates that the as-obtained Pt-on-Pd_0.85Bi_0.15 NWs and PtPdBi PNPs exhibited much higher electrocatalytic activity and durability for the oxygen reduction reaction (ORR) than the commercial Pt/C catalyst. We expect that this work will provide a promising strategy for the development of efficient ORR electrocatalysts and can also be extended to the preparation of other nanowires or hetero-nanostructures with desirable functions

Fe₅C₂ Nanoparticles: A Facile Bromide-Induced Synthesis and as an Active Phase for Fischer–Tropsch Synthesis

Iron carbide nanoparticles have long been considered to have great potential in new energy conversion, nanomagnets, and nanomedicines. However, the conventional relatively harsh synthetic conditions of iron carbide hindered its wide applications. In this article, we present a facile wet-chemical route for the synthesis of Hägg iron carbide (Fe₅C₂) nanoparticles, in which bromide was found to be the key inducing agent for the conversion of Fe­(CO)₅ to Fe₅C₂ in the synthetic process. Furthermore, the as-synthesized Fe₅C₂ nanoparticles were applied in the Fischer–Tropsch synthesis (FTS) and exhibited intrinsic catalytic activity in FTS, demonstrating that Fe₅C₂ is an active phase for FTS. Compared with a conventional reduced-hematite catalyst, the Fe₅C₂ nanoparticles showed enhanced catalytic performance in terms of CO conversion and product selectivity

Hybrid of Co₃Sn₂@Co Nanoparticles and Nitrogen-Doped Graphene as a Lithium Ion Battery Anode

A facile strategy was designed for the fabrication of hybrid of Co₃Sn₂@Co nanoparticles (NPs) and nitrogen-doped graphene (NG) sheets through a hydrothermal synthesis, followed by annealing process. Core–shell architecture of Co₃Sn₂@Co pin on NG is designed for the dual encapsulation of Co₃Sn₂ with adaptable ensembles of Co and NG to address the structural and interfacial stability concerns facing tin-based anodes. In the resulted unique architecture of Co₃Sn₂@Co–NG hybrid, the sealed cobalt cover prevents the direct exposer of Sn with electrolyte because of encapsulated structure and keeps the structural and interfacial integrity of Co₃Sn₂. However, the elastically strong, flexible and conductive NG overcoat accommodates the volume changes and therefore brings the structural and electrical stabilization of Co₃Sn₂@Co NPs. As a result, Co₃Sn₂@Co–NG hybrid exhibits extraordinary reversible capacity of 1615 mAh/g at 250 mA/g after 100 cycles with excellent capacity retention of 102%. The hybrid bears superior rate capability with reversible capacity of 793.9 mAh/g at 2500 mA/g and Coulombic efficiency nearly 100%

Sulfur-Doped Carbon for Potassium-Ion Battery Anode: Insight into the Doping and Potassium Storage Mechanism of Sulfur

The sulfur doping strategy has been attracting extensive interest in potassium-ion battery carbon anodes for the dual potential of improving the capacity and kinetics of carbon anodes. Understanding the doping and potassium storage mechanism of sulfur is crucial to guide the structural design and optimization of high-performance sulfur-doped carbon anodes. Herein, presenting a laboratory-synthesized sulfur-doped hard carbon (SHC) with a sulfur content of 6.4 at. % as an example, we clarify the sulfur doping mechanism and reveal the role of sulfur in potassium storage. The high sulfur content of SHC stems from the selective substitution of sulfur for carbon and the residual trace of sulfur molecular fragments after sulfurization. As a result, thanks to the multifaceted roles of doped sulfur in potassium storage, about twice as much capacity, rate capability, and cycling stability is achieved for SHC against S-free hard carbon at the same test conditions. Furthermore, potassium-ion hybrid capacitors assembled based on an SHC anode demonstrate high energy/power density (139 Wh kg–1/7.3 kW kg–1), along with an extraordinary cycling stability

A Versatile Route toward the Electromagnetic Functionalization of Metal–Organic Framework-Derived Three-Dimensional Nanoporous Carbon Composites

Designable electromagnetic parameters accompanied by a low density of metal–organic framework (MOF)-derived metal/carbon composites are essential prerequisites for excellent microwave-absorbing materials. However, the conventional route is confined to slight modification of the physicochemical properties of metal species and carbon, which also restricts the functionalization of MOF-derived materials. Here, a facile technique has been improved by making full use of highly porous structure to uniformly introduce metallic Co nanoparticles into carbon matrix derived from Cu₃(btc)₂. Through changing the starting amount of Co sources, the composition of the final products can be tuned, offering an effective route to control electromagnetic properties. Multiple attenuation mechanisms are employed to realize excellent reflection loss performance, which can be clarified by modified equivalent circuit mode. Effective frequency bandwidth (<i>f</i>_e) over the whole X band can be obtained by optimizing interfacial polarization through changing interface area and electrical conductivity. Broad <i>f</i>_e covering almost the whole K_u band from 12.3 to 18 GHz with a thin thickness of 1.85 mm can be gained through improving impedance matching and enhancing conduction loss. The present work not only sheds light on the easy fabrication of high-performance lightweight microwave-absorbing materials but also paves the way for extending functionalities of MOF-derived carbon composites

Multifunctional Metal Rattle-Type Nanocarriers for MRI-Guided Photothermal Cancer Therapy

In the past decade, numerous species of nanomaterials have been developed for biomedical application, especially cancer therapy. Realizing visualized therapy is highly promising now because of the potential of accurate, localized treatment. In this work, we first synthesized metal nanorattles (MNRs), which utilized porous gold shells to carry multiple MR imaging contrast agents, superparamagnetic iron oxide nanoparticles (SPIONs), inside. A fragile wormpore-like silica layer was manipulated to encapsulate 8 nm oleylamine SPIONs and mediate the <i>in situ</i> growth of porous gold shell, and it was finally etched by alkaline solution to obtain the rattle-type nanostructure. As shown in the results, this nanostructure with unique morphology could absorb near-infrared light, convert to heat to kill cells, and inhibit tumor growth. As a carrier for multiple SPIONs, it also revealed good function for <i>T</i>₂-weighted MR imaging in tumor site. Moreover, the rest of the inner space of the gold shell could also introduce potential ability as nanocarriers for other cargos such as chemotherapeutic drugs, which is still under investigation. This metal rattle-type nanocarrier may pave the way for novel platforms for cancer therapy in the future

Efficient and Lightweight Electromagnetic Wave Absorber Derived from Metal Organic Framework-Encapsulated Cobalt Nanoparticles

Porous-carbon-based nanocomposites are gaining tremendous interest because of good compatibility, lightweight, and strong electromagnetic wave absorption. However, it is still a great challenge to design and synthesize porous-carbon-based composites with strong absorption capability and broad frequency bandwidth. Herein, a facile and effective method was developed to synthesize Co magnetic nanoparticles/metal organic framework (MOF) (Co NPs/ZIF-67) nanocomposites. Co NPs/porous C composites were subsequently obtained by annealing Co NPs/ZIF-67 nanocomposites at different temperatures under an inert atmosphere. The carbonized nanocomposites showed highly efficient electromagnetic wave absorption capability. Specifically, the optimal composite (i.e., Co/C-700) possessed a maximum reflection loss (RL) value of −30.31 dB at 11.03 GHz with an effective absorption bandwidth (RL ≤ −10 dB) of 4.93 GHz. The electromagnetic parameters and the absorption performance of the composites are readily tunable by adjusting the carbonization temperature and the concentration of Co NPs in the composites. Because of the combination of good impedance matching, dual-loss mechanism, and the synergistic effect between Co NPs and porous carbon composites, these Co NPs/MOF-derived composites are attractive candidates for electromagnetic wave absorbers

Multifunctional Nitrogen-Doped Loofah Sponge Carbon Blocking Layer for High-Performance Rechargeable Lithium Batteries

Low-cost, long-life, and high-performance lithium batteries not only provide an economically viable power source to electric vehicles and smart electricity grids but also address the issues of the energy shortage and environmental sustainability. Herein, low-cost, hierarchically porous, and nitrogen-doped loofah sponge carbon (N-LSC) derived from the loofah sponge has been synthesized via a simple calcining process and then applied as a multifunctional blocking layer for Li–S, Li–Se, and Li–I₂ batteries. As a result of the ultrahigh specific area (2551.06 m² g^–1), high porosity (1.75 cm³ g^–1), high conductivity (1170 S m^–1), and heteroatoms doping of N-LSC, the resultant Li–S, Li–Se, and Li–I₂ batteries with the N-LSC-900 membrane deliver outstanding electrochemical performance stability in all cases, i.e., high reversible capacities of 623.6 mA h g^–1 at 1675 mA g^–1 after 500 cycles, 350 mA h g^–1 at 1356 mA g^–1 after 1000 cycles, and 150 mA h g^–1 at 10550 mA g^–1 after 5000 cycles, respectively. The successful application to Li–S, Li–Se, and Li–I₂ batteries suggests that loofa sponge carbon could play a vital role in modern rechargeable battery industries as a universal, cost-effective, environmentally friendly, and high-performance blocking layer

Ultra-large-scale Synthesis of Fe₃O₄ Nanoparticles and Their Application for Direct Coal Liquefaction

Ultra-large-scale synthesis of iron oxide nanoparticles (875 g) has been achieved in a single reaction via a facile solution-based dehydration process. The obtained nanoparticles capped with hydrophobic oleic acid ligands are magnetite with the average size of 5 nm. The synthesized samples exhibit a higher catalytic activity toward the direct coal liquefaction (DCL) than the commercial Fe₃O₄ powders. The conversion, oil yield, and liquefaction degree with the synthesized Fe₃O₄ nanoparticles are 89.6, 65.1, and 77.3%, respectively. The excellent catalytic performance of the synthesized Fe₃O₄ nanoparticles can be attributed to their extremely small size and high dispersity. This facile approach to prepare highly active nanocatalyst for the DCL will be applicable for future industrial processes

Construction of Synergistic Fe₅C₂/Co Heterostructured Nanoparticles as an Enhanced Low Temperature Fischer–Tropsch Synthesis Catalyst

Iron and cobalt catalysts are two major categories for commercial Fischer–Tropsch synthesis (FTS) catalysts. The two types of catalysts have distinct merits and shortcomings while they are largely supplementary to each other. However, until now, there has been a lack of an efficient way to properly combine those two catalysts into a synergistic one which possesses the benefits of both catalysts. Herein, the Fe₅C₂/Co heterostructured nanoparticles (NPs) were constructed by a secondary growth strategy, where the Fe/Co molar ratio can be tuned from 3.3 to 25. Based on the FTS reaction evaluation, we observed that only with 0.6 wt % Co (Fe/Co = 12) incorporated, the Fe₅C₂/Co catalyst exhibits an activity four times higher than that of pure Fe₅C₂ catalyst at low temperature. In this catalyst, Co was responsible for the CO dissociation while Fe₅C₂ was responsible for the chain growth at 220 °C. The synergistic effect of both sites may lead to enhanced performance in FTS reaction. This result provides a perspective for the construction of Fe–Co bimetallic FTS catalysts