Electrochemical properties of Ebonex®/Pt anodes

The electrochemical behavior of platinized Ebonex® was studied. The electrochemical and semiconductor properties of electrodes can be varied within wide limits by thermal treatment of Ebonex®/Pt, which selectively affects the electrocatalytic activity of anodes in the oxygen evolution reaction. The reduction peak of platinum oxides on the cyclic voltammetry (CV) curves can be used as a correlation parameter when evaluating the electrocatalytic activity of Ebonex®/Pt electrodes in the oxygen evolution reaction.     

The role of crystallization parameters for the synthesis of germanosilicate with UTL topology

The investigation of the critical synthesis parameters of germanosilicate of UTL topology, possessing 14- and 12-rings, has been carried out in detail. (6R,10S)-6,10-Dimethyl-5-azoniaspiro[4.5]decane hydroxide was used as the structure-directing agent (SDA). The kinetics of the synthesis, the role of the Si/Ge ratio in the synthesis mixture, and the effect of the calcination procedure were investigated in relation to the crystallinity and textural properties of the synthesized material. The optimum synthesis time was found to be six days for Si/Ge and (Si+Ge)/SDA molar ratios of 2 and 1.7, respectively. The UTL zeolite crystallizes as small sheets of 10 mum in size. The micropore volume of the best crystals is 0.22 cm(3) g(-1) with a micropore diameter of 1.05 nm, based on DFT and Saito-Foley analyses of adsorption data.     

Atomic-Scale Mapping of Impurities in Partially Reduced Hollow TiO2 Nanowires

The incorporation of impurities during the chemical synthesis of nanomaterials is usually uncontrolled and rarely reported because of the formidable challenge in measuring trace amounts of often light elements with sub-nanometer spatial resolution. And yet, these foreign elements (introduced by doping, for example) influence functional properties. We demonstrate how the hydrothermal growth and a partial reduction reaction on hollow TiO₂ nanowires leads to the introduction of parts per millions of boron, sodium, and nitrogen. This doping explains the presence of oxygen vacancies and reduced Ti states at the surface, which enhance the functional properties of TiO₂. Our results were obtained on model metal oxide nanomaterials and they shed light on a general process that leads to the uncontrolled incorporation of trace impurities in TiO₂, thereby, having a strong effect on applications in energy-harvesting.     

The Common Intermediates of Oxygen Evolution and Dissolution Reactions during Water Electrolysis on Iridium

Understanding the pathways of catalyst degradation during the oxygen evolution reaction is a cornerstone in the development of efficient and stable electrolyzers, since even for the most promising Ir based anodes the harsh reaction conditions are detrimental. The dissolution mechanism is complex and the correlation to the oxygen evolution reaction itself is still poorly understood. Here, by coupling a scanning flow cell with inductively coupled plasma and online electrochemical mass spectrometers, we monitor the oxygen evolution and degradation products of Ir and Ir oxides in situ. It is shown that at high anodic potentials several dissolution routes become possible, including formation of gaseous IrO₃. On the basis of experimental data, possible pathways are proposed for the oxygen‐evolution‐triggered dissolution of Ir and the role of common intermediates for these reactions is discussed.     

Electrochemical On‐line ICP‐MS in Electrocatalysis Research

Electrocatalyst degradation due to dissolution is one of the major challenges in electrochemical energy conversion technologies such as fuel cells and electrolysers. While tendencies towards dissolution can be grasped considering available thermodynamic data, the kinetics of material's stability in real conditions is still difficult to predict and have to be measured experimentally, ideally in‐situ and/or on‐line. On‐line inductively coupled plasma mass spectrometry (ICP‐MS) is a technique developed recently to address exactly this issue. It allows time‐ and potential‐resolved analysis of dissolution products in the electrolyte during the reaction under dynamic conditions. In this work, applications of on‐line ICP‐MS techniques in studies embracing dissolution of catalysts for oxygen reduction (ORR) and evolution (OER) as well as hydrogen oxidation (HOR) and evolution (HER) reactions are reviewed.     

Anodic oxidation of Cr3+ ions in a chromium electroplating bath on Pt and composite TiO x /PtO y

The effect of various factors (anodic current density, composition of electrolyte, electrode material) on current efficiency of the anodic reaction of formation of Cr(VI) ions is established on Pt and composite TiO _x /PtO _y under electrolysis of solutions containing Cr³⁺ ions. It is shown that the current efficiency values of Cr(VI) on TiO _x /PtO _y decrease at an increase in the active layer thickness and increase in the electrode treatment temperature. It is found that the major part of Cr(VI) compounds formed on the anode is reduced on the cathode and as a result of homogeneous chemical reactions in the bulk of electrolyte.     

Anomalous selective reflection in cholesteryl oleyl carbonate – nematic 5CB mixtures and effects of their doping by single-walled carbon nanotubes

Liquid crystalline (LC) mixtures of cholesteryl oleyl carbonate (COC) and 4-pentyl-4'-cyanobiphenyl (5CB) as well as dispersions of single-walled carbon nanotubes (NTs) in these mixtures were studied by means of selective reflection measurements, differential scanning calorimetry (DSC) and optical microscopy. The relative mass of COC in a mixture X was varied between 0.4 and 1.0, the temperature range of measurements was between 284 and 314 K, and concentration of NTs was fixed at 0.1%. Two important anomalies were noted: (1) the cholesteric to smectic-A transition temperature increased on dilution of COC by non-smectogenic 5CB in the concentration range 0.8 < X < 1 and (2) the reciprocal pitch versus 5CB concentration dependence was essentially linear, in contrast to behaviour commonly observed in nematic-cholesteric mixtures. A model of molecular arrangement in the mixtures, accounting for the possibility of integration of 5CB dimers and monomers between COC molecules and presumably explaining the experimental data, was proposed. The helical pitch of the cholesteric mixtures remained practically unchanged upon doping by NTs, and only slight widening of the selective reflection peaks was noted. The obtained results allow considering the COC + 5CB mixtures as promising matrices for composite materials on the basis of liquid crystals and NTs.     

Synthesis, structure and magnetic properties of porous magnetic composite, based on MCM-41 molecular sieve with Fe3O4 nanoparticles

Porous magnetic composites were prepared by the synthesis of molecular sieve MCM-41 in the presence of Fe₃O₄ nanoparticles with average diameter of 15 nm. Nanoparticles were captured by porous silica matrix MCM-41, which resulted in their incorporation, as it was confirmed by TEM, SEM and X-ray diffraction. The materials possessed high surface area (392-666 m² g⁻¹), high pore volume (0.39-0.73 cm³ g⁻¹) along with high magnetic response (M_S up to 28.4 emu g⁻¹ at 300 K). Calcination of samples resulted in partial oxidation of Fe₃O₄ to α-Fe₂O₃. The influence of nanoparticles content on sorption and magnetic properties of the composites was shown. No hysteresis was found for the samples at 300 K; at 5 K, H_C was in the range 370-385 G for non-calcinated samples and 350-356 G for calcinated ones.