Cyanogel-derived formation of 3 D nanoporous SnO2-MxOy (M=Ni, Fe, Co) hybrid networks for high-performance lithium storage

Three-dimensional (3 D) nanoporous SnO2 -Mx Oy (M=Fe, Co, Ni, Cu, etc.) hybrid networks possess unique compositional and structural features that are beneficial to lithium storage and are thus anticipated to meet the performance requirements of advanced lithium-ion batteries for transportation and stationary energy storage. Herein, a facile, scalable, and versatile cyanogel-derived method for the construction of 3 D nanoporous SnO2 -Mx Oy hybrid networks was developed for the first time. The formation of 3 D nanoporous SnO2 -NiO, SnO2 -α-Fe2 O3 , and SnO2 -NiO-Co3 O4 hybrid networks was illustrated by using Sn-M cyanogels as precursors. Moreover, the anodic performance of the 3 D nanoporous SnO2 -NiO hybrid network was examined to demonstrate proof of concept. After coating with polypyrrole-derived carbon, the SnO2 -NiO@C hybrid network exhibited superior lithium-storage capabilities in terms of specific capacity, cycling stability, and rate capability.

Straightforward synthesis of bimetallic Co/Pt nanoparticles in ionic liquid: atomic rearrangement driven by reduction-sulfidation processes and Fischer-Tropsch catalysis

Unsupported bimetallic Co/Pt nanoparticles (NPs) of 4.4 ± 1.9 nm can be easily obtained by a simple reaction of [bis(cylopentadienyl)cobalt(ii)] and [tris(dibenzylideneacetone) bisplatinum(0)] complexes in 1-n-butyl-3-methylimidazolium hexafluorophosphate IL at 150 °C under hydrogen (10 bar) for 24 h. These bimetallic NPs display core-shell like structures in which mainly Pt composes the external shell and its concentration decreases in the inner-shells (CoPt3@Pt-like structure). XPS and EXAFS analyses show the restructuration of the metal composition at the NP surface when they are subjected to hydrogen and posterior H2S sulfidation, thus inducing the migration of Co atoms to the external shells of the bimetallic NPs. Furthermore, the isolated bimetallic NPs are active catalysts for the Fischer-Tropsch synthesis, with selectivity for naphtha products.

Phase-segregated Pt-Ni chain-like nanohybrids with high electrocatalytic activity towards methanol oxidation reaction

The phase-segregated Pt-Ni chain-like nanostructures, composed of monometallic counterparts attached to each other, were synthesized via a modified polyol process with the assistance of a small amount of PVP. The molar ratio between Pt and Ni was tuned by simply adjusting the feed ratio of the precursors. High-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS) results reveal that atomic diffusion occurred at the interface of the granular subunits. The negative shift of the Pt4f7/2 peak in the XPS spectra indicates the electron transfer from Ni to Pt atoms, while the strong peaks at around 855.7 eV suggest the surface oxidation of the Ni nanoparticles, which was further confirmed by the cyclic voltammetry (CV) measurement. The electrocatalytic activities of the methanol oxidation reaction (MOR) were found to be higher for the phase-segregated structures relative to those for pure Pt nanoparticles, and the activities followed the sequences of Pt1Ni1 > Pt3Ni1 ∼ Pt2Ni3 > pure Pt. We believe that the modified electronic structures and the existence of nickel hydroxide both contributed to the improved catalytic activities.

Platinum-cobalt bimetallic nanoparticles in hollow carbon nanospheres for hydrogenolysis of 5-hydroxymethylfurfural

The synthesis of 2,5-dimethylfuran (DMF) from 5-hydroxymethylfurfural (HMF) is a highly attractive route to a renewable fuel. However, achieving high yields in this reaction is a substantial challenge. Here it is described how PtCo bimetallic nanoparticles with diameters of 3.6 ± 0.7 nm can solve this problem. Over PtCo catalysts the conversion of HMF was 100% within 10 min and the yield to DMF reached 98% after 2 h, which substantially exceeds the best results reported in the literature. Moreover, the synthetic method can be generalized to other bimetallic nanoparticles encapsulated in hollow carbon spheres.

From Pt-rich dendrites to Ni-rich cuboctahedrons: structural evolution and electrocatalytic property studies

The composition and morphology evolution for Pt_xNi_1−x (0 < x < 1) nanoalloys was achieved by adjusting the growth kinetics, which were found different under different temperatures. The structure-dependent electrocatalytic performance was evaluated with MOR as the model reaction.

Direct growth of NiCo2O4 nanostructures on conductive substrates with enhanced electrocatalytic activity and stability for methanol oxidation

In this report, NiCo2O4 nanostructures with different morphologies were directly grown on conductive substrates (stainless steel and ITO) by a facile electrodeposition method in addition to a post-annealing process. The morphology changes on different conductive substrates are discussed in detail. The NiCo2O4 on stainless steel (SS) had a high surface area (119 m(2) g(-1)) and was successfully used in the electrocatalytic oxidation of methanol. The electrocatalytic performance was investigated by cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS) measurements. Impressively, the NiCo2O4 showed much higher electrocatalytic activity, lower overpotential and greater stability compared to that of only NiO or Co3O4 synthesized by the same method. The higher electrocatalytic activity is due to the high electron conductivity, large surface area of NiCo2O4 and the fast ion/electron transport in the electrode and at the electrolyte-electrode interface. This is important for further development of high performance non-platinum electrocatalysts for application in direct methanol fuel cells.

All-metal layer-by-layer films: bimetallic alternate layers with accessible mesopores for enhanced electrocatalysis

We have prepared multilayer mesoporous bimetallic (Pt/Pd) alternating films by layer-by-layer (LbL) electrochemical deposition. Because of the high surface area and heterometallic interfacial atomic contacts, enhanced electrocatalytic activity for methanol oxidation reaction is realized. This novel LbL approach allows optimization of the electrocatalytic performance through precise tuning of the thickness of each layer.