Vacancy defects of catalysts have been extensively studied and proven to be beneficial to various electrocatalytic reactions. Herein, an ultra‐stable three‐dimensional PtCu nanowire network (NNW) with ultrafine size, self‐supporting rigid structure, and Cu vacancy defects has been developed. The vacancy defect‐rich PtCu NNW exhibits an outstanding performance for the oxygen reduction reaction (ORR), with a mass activity 14.1 times higher than for the commercial Pt/C catalyst (20 %.wt, JM), which is currently the best performance. The mass activity of the PtCu NNW for methanol oxidation reaction (MOR) is 17.8 times higher than for the commercial Pt/C catalyst. Density‐functional theory (DFT) calculations indicate that the introduction of Cu vacancies enhances the adsorption capacity of Pt atoms to the HO* intermediate and simultaneously weakens the adsorption for the O* intermediate. This work presents a facile strategy to assemble efficient electrocatalysts with abundant vacancy defects, at the same time, provides an insight into the ORR mechanism in acidic solution. 相似文献
Zeolites are widely used in many commercial processes, mostly as catalysts or adsorbents. Understanding their intimate structure at the nanoscale is the key to control their properties and design the best materials for their ever increasing uses. Herein, we report a new and controllable fluoride treatment for the non‐discriminate extraction of zeolite framework cations. This sheds new light on the sub‐structure of commercially relevant zeolite crystals: they are segmented along defect zones exposing numerous nanometer‐sized crystalline domains, separated by low‐angle boundaries, in what were apparent single‐crystals. The concentration, morphology, and distribution of such domains analyzed by electron tomography indicate that this is a common phenomenon in zeolites, independent of their structure and chemical composition. This is a milestone to better understand their growth mechanism and rationally design superior catalysts and adsorbents. 相似文献
Single‐walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with enhanced thermoelectric properties were prepared by combining in situ polymerization and solution processing. Conductive atomic force microscopy and X‐ray diffraction measurements confirmed that solution processing and strong π–π interactions between the PANI and SWNTs induced the PANI molecules to form a highly ordered structure. The improved degree of order of the PANI molecular arrangement increased the carrier mobility and thereby enhanced the electrical transport properties of PANI. The maximum in‐plane electrical conductivity and power factor of the SWNTs/PANI composite films reached 1.44×103 S cm?1 and 217 μW m?1 K?2, respectively, at room temperature. Furthermore, a thermoelectric generator fabricated with the SWNTs/PANI composite films showed good electric generation ability and stability. A high power density of 10.4 μW cm?2 K?1 was obtained, which is superior to most reported results obtained in organic thermoelectric modules. 相似文献
Hematite has been considered as one of the most promising photoanode candidates for solar water‐splitting. However, its photoelectrochemical (PEC) efficiency is largely constrained by its sluggish oxygen evolution reaction. In this work, the photoelectrochemical performance of hematite was investigated in electrolytes containing different sacrificial agent. The photocurrent densities, onset potential, charge transfer resistance, Helmholtz capacitance at semiconductor liquid junctions (SCLJs), and their correlations were systematically studied. It was found that the onset potential is around the CH peak potential and is related to the photovoltage. The surface states pinning the Fermi levels of the hematite photoanode are related to the adsorbed water molecules regardless of the sacrificial agents in the electrolyte. 相似文献
Five dinuclear lanthanide complexes [Ln2L2(NO3)2(OAc)4] · 2CH3CN [Ln = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ), and Er ( 5 )] [L = 2‐((2‐pyridinylmethylene)hydrazine)ethanol] were synthesized from the reactions of Ln(NO3)3 · 6H2O with L and CH3COOH in the presence of triethylamine. Their crystal structures were determined. They show similar dinuclear cores with the two lanthanide ions bridged by four acetate ligands in the μ2‐η1:η2 and μ2‐η1:η1 bridging modes. Each LnIII ion in complexes 1 – 5 is further chelated by one L ligand and one nitrate ion, leading to the formation of a nine‐coordinated mono‐capped square antiprism arrangement. The dinuclear molecules in 1 – 5 are consolidated by hydrogen bonds and π ··· π stacking interactions to build a two‐dimensional sheet. Their magnetic properties were investigated. It revealed antiferromagnetic interactions between the GdIII ions in 1 and ferromagnetic interactions between the TbIII ions in 2 . The profiles of χmT vs. T curves of 3 – 5 reveal that the magnetic properties of 3 – 5 are probably dominated by the thermal depopulation of the Stark sublevels of LnIII ions. 相似文献
A universal simplified strategy was developed to fabricate all-solid-state planar micro-supercapacitors with high areal capacitance (~355 mF/cm2), based on interdigital patterned films of 2D pseudocapacitive MnO2 nanosheets and electrochemically exfoliated graphene. 相似文献
MnO has a high theoretical capacity, moderate discharge plateau, and low polarization when it is used as the anode material in lithium battery. However, the issues that limit its application are its poor conductivity and large volume changes, which can easily result in the collapse of electrode structure during long-term cycling. In the present work, a carbon-coated MnO/graphene 3D-network anode material is synthesized by an electrostatic adsorption of dispersed precipitates precipitation method. The MnO nanoparticles coated by carbon are uniformly distributed on the surface of graphene nanosheets and form a 3D sandwich-like nanostructure. A carbon layer is coated on the surface of MnO nanoparticles, which slows down the volume expansion in the process of lithium intercalation. The graphene nanosheets are cross-linked through carbons in this 3D nanostructure, which provides mechanical support and effective electron conduction pathways during the charge-discharge. The electrochemical tests indicate that the prepared 3D carbon-coated MnO/graphene electrode exhibits an excellent rate capacity of 1247.3 and 713.2 mAh g?1 at 100 and 1000 mA g?1, respectively. The capacity is 792.2 mAh g?1 after long cycle at a current density of 1000 mA g?1. The specific capacity is higher than that of MnO-based composite lithium anode materials currently reported. The superior rate and cycling performances are attributed to the unique 3D-network structure, which provides an effectively conductive network, buffers volume expansion, and prevents falling and aggregation of MnO in the charge and discharge process of the electrode materials. The 3D-structured carbon-coated MnO/graphene anode material will have an excellent application prospect.