Enhancing Efficiency of Nitrate Reduction to Ammonia by Fe and Co Nanoparticle-Based Bimetallic Electrocatalyst.

The green and sustainable electrocatalytic conversion of nitrogen-containing compounds to ammonia is currently in high demand in order to replace the eco-unfriendly Haber-Bosch process. Model catalysts for the nitrate reduction reaction were obtained by electrodeposition of metal Co, Fe, and bimetallic Fe/Co nanoparticles from aqueous solutions onto a graphite substrate. The samples were characterized by the following methods: SEM, XRD, XPS, UV-vis spectroscopy, cyclic (and linear) voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. In addition, the determination of the electrochemically active surface was also performed for all electrocatalysts. The best electrocatalyst was a sample containing Fe-nanoparticles on the layer of Co-nanoparticles, which showed a Faradaic efficiency of 58.2% (E = -0.785 V vs. RHE) at an ammonia yield rate of 14.6 µmol h-1 cm-2 (at ambient condition). An opinion was expressed to elucidate the mechanism of coordinated electrocatalytic action of a bimetallic electrocatalyst. This work can serve primarily as a starting point for future investigations on electrocatalytic conversion reactions to ammonia using model catalysts of the proposed type.

Is a 2D Nanostructured Surface Capable of Changing the Corrosion and Magnetic Properties of an Amorphous Alloy?

In this work, an attempt was made to reveal and explain the influence of the process of formation of 2D nanostructures at the surface of an amorphous alloy (an alloy with the composition Co75Si15Fe5Cr4.5Al0.5 (in at.%) was used for this purpose) on the corrosion and magnetic properties of such an alloy. Two-dimensional nanostructures (nanocells of 100-150 nm in size, which were obtained by anodizing the initial sample in an ionic liquid) are essentially a pattern on the surface of the sample, and they cannot completely cover and block the surface from external effects. It was postulated that the presence of these nanostructures during corrosion and magnetic tests has no significant effect. However, a noticeable inhibition effect was observed during corrosion tests and a less noticeable (but still detectable) effect was observed during magnetic tests. The authors believe that the effect obtained, with a detailed study, can be used to increase the corrosion resistance and to improve the properties of traditional magnetic materials.

Electrochemical Synthesis of Unique Nanomaterials in Ionic Liquids.

The review considers the features of the processes of the electrochemical synthesis of nanostructures in ionic liquids (ILs), including the production of carbon nanomaterials, silicon and germanium nanoparticles, metallic nanoparticles, nanomaterials and surface nanostructures based on oxides. In addition, the analysis of works on the synthesis of nanoscale polymer films of conductive polymers prepared using ionic liquids by electrochemical methods is given. The purpose of the review is to dwell upon an aspect of the applicability of ILs that is usually not fully reflected in modern literature, the synthesis of nanostructures (including unique ones that cannot be obtained in other electrolytes). The current underestimation of ILs as an electrochemical medium for the synthesis of nanomaterials may limit our understanding and the scope of their potential application. Another purpose of our review is to expand their possible application and to show the relative simplicity of the experimental part of the work.

Nanorolls Decorated with Nanotubes as a Novel Type of Nanostructures: Fast Anodic Oxidation of Amorphous Fe-Cr-B Alloy in Hydrophobic Ionic Liquid.

The formation of oxide nanorolls decorated with nanotubes during anodic oxidation of amorphous Fe70Cr15B15 alloy in hydrophobic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (IL) was revealed. The unusual architecture was observed for the first time on the surface of amorphous alloy. The generation of the novel type of nanostructure by electrochemical oxidation of the amorphous Fe70Cr15B15 alloy occurs only in hydrophobic ionic liquid and in the presence of the natural oxide film at the surface. Anodization of the oxide-free metal surface of the amorphous Fe70Cr15B15 alloy to be achieved by the treatment of the electrode with benzoic acid was found to result in no formation of both nanorolls and nanotubes. Electrochemical behavior of the amorphous Fe70Cr15B15 alloy in ionic liquid was proved to depend strongly on the state of the electrode surface before oxidation. The influence of the state of the surface of amorphous Fe70Cr15B15 alloy leading to the nanostructure formation was studied by means of preliminary partial etching with benzoic acid of various concentrations.

Platinum Nanoparticles on Sintered Metal Fibers Are Efficient Structured Catalysts in Partial Methane Oxidation into Synthesis Gas.

Efficient structured catalysts of partial methane oxidation into synthesis gas were obtained by electrochemical modification of the surface of sintered FeCrAl alloy fibers in an ionic liquid BMIM-NTf2 with further introduction of platinum nanoparticles. It was shown that etching and electrochemical modification of sintered FeCrAl alloy fibers result in a decrease of the surface aluminum content. With an increase of the reaction temperature to 900 °C, the methane conversion reaches 90% and the selectivity to CO increases significantly to achieve 98%. The catalysts with a Pt loading of 1 × 10-4 wt % demonstrate high activity and selectivity as well as TOF in synthesis gas production by the CH4 + O2 reaction at 850-900 °C. To trace the composition and structure evolution of the catalysts, XRD and SEM methods were used.

Surface state of sacrificial copper electrode by electropolishing in hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

Anodic dissolution of natural surface-oxidized, air-annealed, cathodically reduced, and cathodically deposited copper in hydrophobic ionic liquid 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide under galvanostatic conditions by means of gravimetric measurements was studied. The resulting samples were mirror-like oxide-free copper pattern. The mechanism of the electropolishing of oxidized copper surface was considered. The consequent anodic reactions Cu2O - 1e = Cu(+) + CuO, CuO - 2e = Cu(2+) + O, and Cu - 1e = Cu(+) take place. The electropolishing itself occurs over oxygen-free copper surface due to competitive residual water discharge in the pits and copper dissolution on the roughness.