A hierarchical high-performance electrode with nanoacanthine-style polyaniline (PANI) deposited onto a carbon nanofiber/graphene oxide (CNF/GO) template was successfully prepared via an in situ polymerization process. The morphology analysis shows that introducing one-dimensional (1D) CNF could significantly decrease/inhibit the staking of laminated GO to form an open-porous CNF/GO architecture. Followed with in situ facial deposition of PANI, the as-synthesized PANI modified CNF/GO exhibits three-dimensional (3D) hierarchical layered nanoarchitecture, which favors the diffusion of the electrolyte ions into the inner region of active materials. The hierarchical free-standing electrodes were directly fabricated into sandwich structured supercapacitors using 1 M H2SO4 as the electrolyte showing a significant specific capacitance of 450.2 F/g at the voltage scan rate of 10 mV/s. The electrochemical properties of the hierarchical structure can be further improved by a reduction procedure of GO before the deposition of PANI.
Recent progress in the controllable synthesis of ultrathin metallic nanoarchitectures utilizing functional surfactants via a self-assembly mechanism and the corresponding electrocatalytic performance has been thoroughly reviewed.
Inorganic nanodendrites (NDs) have become a kind of advanced nanomaterials with broad application prospects because of their unique branched architecture. The structural characteristics of nanodendrites include highly branched morphology, abundant tips/edges and high-index crystal planes, and a high atomic utilization rate, which give them great potential for usage in the fields of electrocatalysis, sensing, and therapeutics. Therefore, the rational design and controlled synthesis of inorganic (especially noble metals) nanodendrites have attracted widespread attention nowadays. The development of synthesis strategies and characterization methodology provides unprecedented opportunities for the preparation of abundant nanodendrites with interesting crystallographic structures, morphologies, and application performances. In this review, we systematically summarize the formation mechanisms of noble metal nanodendrites reported in recent years, with a special focus on surfactant-mediated mechanisms. Some typical examples obtained by innovative synthetic methods are then highlighted and recent advances in the application of noble metal nanodendrites are carefully discussed. Finally, we conclude and present the prospects for the future development of nanodendrites. This review helps to deeply understand the synthesis and application of noble metal nanodendrites and may provide some inspiration to develop novel functional nanomaterials (especially electrocatalysts) with enhanced performance.
Quaternary ammonium salts are well-known zeolite structure-directing agents. However, cationic surfactants with quaternary ammonium head groups are known to fail to function as SDAs of zeolites because their long surfactant chains disrupt the ordered growth of the zeolite crystals. In this study, we found that ZSM-5 and silicalite-1 can be formed very easily with appropriate synthesis compositions over a large temperature range of 100-200 °C. The (13)C CP/MAS data for surfactants in ZSM-5 combined with elemental analysis indicated that the surfactants were in more rigid, isolated environments and did not undergo decomposition. The surfactant head groups can serve as structure-directing agents for zeolites, and the long chains become isolated and occupy the micropores. Our findings provide a new insight into the molecular factors governing the formation of inorganic-organic microporous materials, which opens up new possibilities for the elaborate fabrication of mesoporous zeolites.
Core-shell nanohybrids containing cheap inorganic nanocrystals and nanocarbon shells are promising electrocatalysts for water splitting or other renewable energy options. Despite that great progress has been achieved, biomimetic synthesis of metal phosphates@nanocarbon core-shell nanohybrids remains a challenge, and their use for electrocatalytic oxygen evolution reaction (OER) has not been explored. In this paper, novel nanohybrids composed of coralloid Co2P2O7 nanocrystal cores and thin porous nanocarbon shells are synthesized by combination of the structural merits of supramolecular polymer gels and a controllable thermal conversion technique, i.e., temperature programmable annealing of presynthesized supramolecular polymer gels that contain cobalt salt and phytic acid under a proper gas atmosphere. Electrocatalytic tests in alkaline solution show that such nanohybrids exhibit greatly enhanced electrocatalytic OER performance compared with that of Co2P2O7 nanostructure. At a current density of 10 mA cm(-2), their overpotential is 0.397 V, which is much lower than that of Co2P2O7 nanostructures, amorphous Co-Pi nanomaterials, Co(PO3)2 nanosheets, Pt/C, and some reported OER catalysts, and close to that of commercial IrO2. Most importantly, both of their current density at the overpotential over 0.40 V and durability are superior to those of IrO2 catalyst. As revealed by a series of spectroscopic and electrochemical analyses, their enhanced electrocatalytic performance results from the presence of thin porous nanocarbon shells, which not only improve interfacial electron penetration or transfer dynamics but also vary the coordination environment and increase the number of active 5-coordinated Co(2+) sites in Co2P2O7 cores.
Abstract Palladium (Pd)‐catalyzed radical oxidative C−H carbonylation of alkanes is a useful method for functionalizing hydrocarbons, but there is still a lack of understanding of the mechanism, which restricts the application of this reaction. In this work, density functional theory (DFT) calculations were carried out to study the mechanism for a Pd‐catalyzed radical esterification reaction. Two plausible reaction pathways have been proposed and validated by DFT calculations. The computational results reveal that the generated alkyl radical prefers to add to the carbon monoxide (CO) molecule to form a carbonyl radical before bonding with the Pd species. Radical addition onto Pd followed by CO migratory insertion was unfavorable owing to the high energy barrier of the migratory insertion step. The regioselectivity of the C(sp 3 )−H carbonylation was also investigated by DFT. The results show that the regioselectivity is controlled by both the bond dissociation energy of the reacting C−H bond and the stability of the corresponding generated carbon radical. Competitive side reactions also affected the yield and regioselectivity owing to the rapid consumption of the stable radical intermediate.
Two new Sc-based oxyborates, ScMO(BO3) (M = Ca and Cd), have been synthesized, which possess interesting edge-sharing sandwich-like chains and UV cut-off edges.
Abstract Mesoporous MFI zeolites (MMZs) have been constructed by using the surfactant‐containing azobenzene segment in the hydrophobic tail. The cylindrical π–π stacking of azeobenzene groups is considered to be the key factor to form the ordered mesostructure through cooperative structural matching and the rearrangement of MFI frameworks. The mesostructure has been tuned from a disordered hierarchical arrangement into an ordered 2D square p 4 mm structure by changing the length of the alkyl chain between the diquaternary ammonium head group and azobenzene group. The geometric matching between the MFI zeolitic framework and the alkyl chain length plays an important role in the construction of the crystallographically correlated mesostructure with 2D square ordering. A combination of X‐ray diffraction patterns and electron microscopy studies provides visible evidence for the mesostructural transformation from a short‐range hexagonal or lamellar ordering to 2D square mesostructure.
PdPtP nanodendrites were prepared by a post-phosphating method. Due to their well-designed structure and composition, the EOR activity of the PtPdP NDs is significantly increased to 14.3 A mg
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