•PdAg alloy nanotubes with porous walls were prepared.•The as-prepared catalyst exhibits superior activity for ethanol oxidation.•The activity derives from structural effect and the unique nanostructure.Direct alcohol fuel cells (DAFCs) has been recognized as a green and substantial energy source in the near future. Due to the excellent electrocatalytic activities of palladium-based electrocatalysts for alcohol oxidation in alkaline medium, controllable synthesis of Pd-based bimetallic nanocrystals to maximize its activity while simultaneously decreasing the required amount of Pd is very important for the commercializaiton of DAFCs. Here, a novel PdAg naocrystal with unique structure is synthesized by the galvanic replacement reaction between pre-synthesized Ag nanowires and palladium precursor. X-ray diffraction and high-resolution transmission electron microscopy demonstrate that the obtained PdAg naocrystals display a tubular alloy nanostructure with hollow interiors and porous walls. Moreover, the electrochemical studies indicate that the as-prepared PdAg alloy nanotubes (PdAg-ANTs) exhibit excellent electrocatalytic activity and stability towards ethanol electrooxidation in alkaline media, showing its great potential for use as anode catalysts in alkaline DAFCs. The enhanced electrocatalytic activity of the prepared PdAg-ANTs can be attributed to the formation of alloy between Ag and Pd atoms, structural effect and the unique nanostructure.Download high-res image (295KB)Download full-size image

Recently, sodium-ion batteries (SIBs) have attracted increasing attention as an important supplement or alternative to lithium ion batteries (LIBs) due to the abundance of sodium resources and its much lower cost. A critical issue and great challenge in current battery research for the extensive application of SIBs is the development of earth-abundant and high-performance electrode materials. In various studies of these electrode materials, Sn-based nanocomposites have been identified as promising anodes for SIBs. In this study, Sn nanoparticles on nitrogen-doped carbon nanofiber composites (Sn@NCNFs) have been synthesized by an electrostatic spinning technique and used as anodes for SIBs. Morphological and structural characterizations indicate that the Sn nanoparticles adhere uniformly on the surface of the nitrogen-doped carbon nanofibers. The corresponding specific capacity can reach over 600 mA h g−1 at 0.1C after 200 cycles. Additionally, these Sn@NCNFs also show excellent high-rate cycling performance and can maintain a capacity of up to 390 mA h g−1 even at an extremely high rate of 1C for over 1000 cycles. The results demonstrate that this Sn@NCNFs composite is a promising anode material with good reversible capacity and cycling performance for SIBs.

Exploitation of high capacity and long-life anode materials is essential for the development of lithium-ion batteries (LIBs) with high energy density. Metal sulfides have shown great potential as anode materials for LIBs due to their high theoretical specific capacity and excellent electronic properties and therefore they are considered as excellent candidates for anode materials. However, structural degradation during cycling and polysulfide dissolution has limited their practical application. In this work, we design a unique 0D/1D heterostructure of carbon coated iron–nickel sulfide nanodots/carbon nanorod through simultaneous decomposition and sulfidation of a bi-metal organic framework template. The resultant nanodots/nanorod heterostructure allows for fast ion/electron transport kinetics, suppresses polysulfide dissolution and ensures structural integrity during the lithiation/delithiation process. Consequently, this carbon coated iron–nickel sulfide nanodots/carbon nanorod structure exhibits a high specific capacity (851.3 mA h g−1 at 0.5C after 200 cycles) and an excellent cycling stability (484.7 mA h g−1 after 1000 cycles at a high rate of 4C).

Oxidized Pt–Ni nanoparticles were deposited on N-doped graphene oxide (NGO) for the hydrolysis of ammonia borane (AB). The optimized Pt3Ni7O–NGO sample shows a high total turnover frequency (TOF) value of 709.6 mol H2 per mol Cat-Pt per min in the hydrolysis of AB, which is one of the best values for Pt-based catalysts to date. Moreover, when calculating all metal contents (mainly Ni, Pt : Ni = 1 : 5) in the hybrid, the total TOF value is still as high as 120.7 mol H2 per mol Cat-metal per min, better than that of pure Pt/C or Pt on NGO. The hybrid also exhibits a good stability with more than 76% activity (TOF = 544.9) after 9 cycles. Synchrotron radiation X-ray absorption spectroscopy reveals that Pt and Ni in the catalyst exhibit a strong interaction through oxygen bonds and the bimetallic structure shows further interaction with the support material. All the components in the hybrid can thus be connected to show a synergetic effect for enhanced catalytic performance. The excellent performance can be related to the unique electronic structure of the hybrid with the synergetic effect, which may also shed light on the design of high-efficiency catalysts for other energy-related applications.

Platinum-based bimetallic nanocatalysts have attracted much attention due to their high-efficiency catalytic performance in energy-related applications such as fuel cell and hydrogen storage, for example, the hydrolytic dehydrogenation of ammonia borane (AB). In this work, a simple and green method has been demonstrated to successfully prepare Pt–M (M = Fe, Co, Ni) NPs with tunable composition (nominal Pt/M atomic ratios of 4:1, 1:1, and 1:4) in aqueous solution under mild conditions. All Pt–M NPs with a small size of 3–5 nm show a Pt fcc structure, suggesting the bimetallic formation (alloy and/or partial core–shell), examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) analysis. The catalytic activities of Pt–M NPs in the hydrolytic dehydrogenation of AB reveal that Pt–Ni NPs with a ratio of 4:1 show the best catalytic activity and even better than that of pure Pt NPs when normalized to Pt molar amount. The Ni oxidation state in Pt–Ni NPs has been suggested to be responsible for the corresponding catalytic activity for hydrolytic dehydrogenation of AB by XAFS study. This strategy for the synthesis of Pt–M NPs is simple and environmentally benign in aqueous solution with the potential for scale-up preparation and the in situ catalytic reaction.Keywords: ammonia borane; bimetallic; hydrolytic dehydrogenation; nanoparticles; XAFS

Recently, sodium-ion batteries (SIBs) have attracted increasing attention as an important supplement or alternative to lithium ion batteries (LIBs) due to the abundance of sodium resources and its much lower cost. A critical issue and great challenge in current battery research for the extensive application of SIBs is the development of earth-abundant and high-performance electrode materials. In various studies of these electrode materials, Sn-based nanocomposites have been identified as promising anodes for SIBs. In this study, Sn nanoparticles on nitrogen-doped carbon nanofiber composites (Sn@NCNFs) have been synthesized by an electrostatic spinning technique and used as anodes for SIBs. Morphological and structural characterizations indicate that the Sn nanoparticles adhere uniformly on the surface of the nitrogen-doped carbon nanofibers. The corresponding specific capacity can reach over 600 mA h g−1 at 0.1C after 200 cycles. Additionally, these Sn@NCNFs also show excellent high-rate cycling performance and can maintain a capacity of up to 390 mA h g−1 even at an extremely high rate of 1C for over 1000 cycles. The results demonstrate that this Sn@NCNFs composite is a promising anode material with good reversible capacity and cycling performance for SIBs.