Evolution of physicochemical and electrocatalytic properties of NiCo2O4 (AB2O4) spinel oxide with the effect of Fe substitution at the A site leading to efficient anodic O2 evolution in an alkaline environment

Within the framework of this work, spinel-type ternary transition metal oxides of nickel, cobalt and iron with the composition Fe_xNi_1−xCo₂O₄ (0 ≤ x ≤ 1) were prepared and tested as promising electrocatalysts for the oxygen evolution reaction (OER) in alkaline water electrolysis. The hydroxide precipitation method was used for the synthesis. The morphology, structure and specific surface area of the prepared electrocatalysts were determined by means of scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, the Brunauer Emmet Teller method and X-ray photo electron spectroscopy. The electrochemical properties were tested by thin-film technique on a rotating disk electrode and in a single-cell laboratory water electrolyzer coupled with electrochemical impedance spectroscopy. The OER studies indicate that substitution of Ni by Fe increases the electrocatalytic activity of the resulting material significantly. The highest activity was achieved for x = 0.1. Whereas the current density obtained using a pure nickel anode in the water electrolysis test was 54 mA cm⁻² at a cell voltage of 1.85 V, in the case of the anode modified with NiCo₂O₄ catalyst the value was 87 mA cm⁻². Using ternary transition metal oxides in the water electrolysis test and under identical conditions, the catalyst with the highest activity displayed a current density of 115 mA cm⁻².     

A spiral shaped regenerative microfluidic fuel cell with Ni‐C based porous electrodes

Microchannel geometry, electrode surface area, and better fuel utilization are important aspects of the performance of a microfluidic fuel cell (MFC). In this communication, a membraneless spiral‐shaped MFC fabricated with Ni as anode and C as a cathode supported over a porous filter paper substrate is presented. Vanadium oxychloride and dilute sulfuric acid solutions are used as fuel and electrolyte, respectively, in this fuel cell system. The device generates a maximum open‐circuit voltage of ~1.2 V, while the maximum energy density and current density generated from the fuel cell are ~10 mW cm^?2 and ~51 mA cm^?2, respectively. The cumulative energy density generated from the device after five cycles are measured as ~200 mW after regeneration of the fuel by applying external voltage. The spiral design of the fuel cell enables improved fuel utilization, rapid diffusive transport of ions, and in‐situ regeneration of the fuel. The present self‐standing spiral‐shaped MFC will eliminate the challenges associated with two inlet membrane‐less fuel cells and has the potential to scale up for commercial application in portable energy generation.     

Monitoring the curing of furan resins through the exothermic heat of reaction

The curing reaction of furan resins was monitored through the exothermic heat of reaction by means of a simple technique. p-Toluene sulphonic acid dissolved in acetone was used to catalyse the curing reaction. A ‘cure rate index’, defined as the maximum temperature rise per unit time per unit mass of the resin, was used as a measure of the rate of cure. The index value increases exponentially with the catalyst concentration. Interestingly, for the same catalyst concentration the index value also increases significantly with the period of ageing of the catalyst solution. A method is developed for deriving the activation energy for the curing reaction from the exothermic heat data for non-isothermal cure. The activation energy is found to increase with resin viscosity and to decrease exponentially with increasing catalyst concentration. Quantitative expressions are derived relating activation energy with catalyst concentration.     

Oxidation of Aqueous Sulphur Dioxide Catalysed by Poly-4-vinylpyridine–Cu(II) Complex. Part 2: Combined Homogeneous and Heterogeneous Phase Oxidation

Aqueous phase oxidation of sulphur dioxide at low concentrations catalysed by a PVP–Cu complex in the solid phase and dissolved Cu(II) in the liquid phase is studied in a rotating catalyst basket reactor (RCBR). The equilibrium adsorption of Cu(II) and S(VI) on PVP particles is found to be of the Langmuir-type. The diffusional effects of S(IV) species in PVP–Cu resin are found to be insignificant whereas that of product S(VI) are found to be significant. The intraparticle diffusivity of S(VI) is obtained from independent tracer experiments. In the oxidation reaction HSO₃⁻ is the reactive species. Both the S(IV) species in the solution, namely SO₂(aq) and HSO₃⁻, get adsorbed onto the active PVP–Cu sites of the catalyst, but only HSO₃⁻ undergoes oxidation. A kinetic mechanism is proposed based on this feature which shows that SO₂(aq) has a deactivating effect on the catalyst. A rate model is developed for the three-phase reaction system incorporating these factors along with the effect of concentration of H₂SO₄ on the solubility of SO₂ in the dilute aqueous solutions of Cu(II). Transient oxidation experiments are conducted at different conditions of concentration of SO₂ and O₂ in the gas phase and catalyst concentration, and the rate parameters are estimated from the data. The observed and calculated profiles are in very good agreement. This confirms the deactivating effect of non-reactive SO₂(aq) on the heterogeneous catalysis. © 1997 SCI.     

Review of the Regulation of Veterinary Drugs and Residues in South Africa

The food safety risk analysis framework of the FAO/WHO is used in the review of veterinary drug and residue regulation in South Africa to determine possible inefficiencies within this system. Results indicate that a variety of challenges relating to the processes of risk assessment, management, and communication do exist, although these occur within a fragmented system of legislation, functions, and structures. Addressing these challenges therefore requires a change to a more collaborative and integrated system. It is indicated that for such a change, the underlying challenges of inadequate horizontal communication, poor conceptualization, and awareness of functions of the system are required to be dealt with.     

Electrochemical synthesis of Li-doped NiFeCo oxides for efficient catalysis of the oxygen evolution reaction in an alkaline environment

Oxygen evolution reaction (OER) is an essential reaction for overall electrochemical water splitting. In this present study, we adopt a facile electrochemical deposition method to synthesize the Li-doped NiFeCo oxides for OER in an alkaline medium. The scanning electron microscopy, X-ray diffraction, Brunauer-Emmet-Teller method and X-ray photo-electron spectroscopy provides the information of morphology, structure, specific surface area and electronic state of the electrocatalysts respectively. Investigates the electrochemical properties by the thin-film technique on a rotating disk electrode and in a single-cell laboratory water electrolyzer connects with electrochemical impedance spectroscopy. Among the catalysts under investigation, Ni_0·9Fe_0·1Co_1·975Li_0·025O₄ exhibits the highest activity towards oxygen evolution reaction, and explains the activity by the oxygen binding energy; such knowledge can be helped to develop better catalyst. We achieve onset over potential 220 mV and receive 10 mA cm^?2 current density at over potential 301 mV with Tafel slope 62 mV dec^?1 in 1 M KOH solution. The results are similar to recently published catalysts in the literature. In water electrolyzer, the Ni_0·9Fe_0·1Co_1·975Li_0·025O₄ modified nickel foam anode exhibits a current density of 143 mA cm^?2 at a cell voltage of 1.85 V in 10 wt% KOH and a temperature of 50 °C.     

Effect of band parameters on interband optical absorption in quantum wire structure of low band gap III–V semiconductors

A generalized theory is presented to study the effect of band parameters on inter band optical absorption in quantum wire structure of III–V compound semiconductors considering the wave-vector ( $\vec{k}$ ) dependence of the optical transition matrix element (OME). The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted to calculate the inter band optical absorption coefficient (IOAC) for a wide range of III–V compound semiconductors like, InAs, InSb, Hg_1?x Cd _x Te and In_1?x Ga _x As _y P_1?y lattice matched to InP, having varied split-off energy band compared to their energy band gap. It has been found that IOAC for quantum wires (QWRs) increases in oscillatory manner with increasing incident photon energy and the positions of peaks of oscillation of the coefficient are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of band energy constants. This effect of band parameters is better revealed from the study of light polarization dependence of the absorption coefficient.     

Characterizing nutrient dynamics with relation to changes in partial pressure of CO2 in a tropical sewage‐fed aquaculture pond situated in a Ramsar wetland

The changes in nutrient dynamics (nitrate, ammonium, silicate, phosphate and iron concentration) vis‐à‐vis partial pressure of CO₂ in water [pCO₂(water)] from tropical sewage‐fed aquaculture ponds (East Kolkota Wetlands, India) were analysed by means of a microcosm. A significant relationship between these nutrient’s removal from the system and reduction in pCO₂(water) was observed (with few exceptions). These water bodies acted as significant sources of CO₂ in pre‐monsoon and monsoon seasons despite having substantial quantity of chlorophyll‐a to make it a net autotrophic system. The study revealed that if conditions favourable for optimum photosynthesis can be maintained in these ponds, the CO₂ source character of these ponds can be reversed. In the post‐monsoon season, when the pH of the water column was high, the system acted as sink for CO₂ which suggests the use of lime to prevent these systems from becoming hypereutrophic and carbon source at the same time.     

Multiscale morphological segmentation of gray-scale images

In this paper, the authors have proposed a method of segmenting gray level images using multiscale morphology. The approach resembles the watershed algorithm in the sense that the dark (respectively bright) features which are basically canyons (respectively mountains) on the surface topography of the gray level image are gradually filled (respectively clipped) using multiscale morphological closing (respectively opening) by reconstruction with isotropic structuring element. The algorithm detects valid segments at each scale using three criteria namely growing, merging and saturation. Segments extracted at various scales are integrated in the final result. The algorithm is composed of two passes preceded by a preprocessing step for simplifying small scale details of the image that might cause over-segmentation. In the first pass feature images at various scales are extracted and kept in respective level of morphological towers. In the second pass, potential features contributing to the formation of segments at various scales are detected. Finally the algorithm traces the contours of all such contributing features at various scales. The scheme after its implementation is executed on a set of test images (synthetic as well as real) and the results are compared with those of few other standard methods. A quantitative measure of performance is also formulated for comparing the methods.     

Super resolution image reconstruction through bregman iteration using morphologic regularization

Multiscale morphological operators are studied extensively in the literature for image processing and feature extraction purposes. In this paper, we model a nonlinear regularization method based on multiscale morphology for edge-preserving super resolution (SR) image reconstruction. We formulate SR image reconstruction as a deblurring problem and then solve the inverse problem using Bregman iterations. The proposed algorithm can suppress inherent noise generated during low-resolution image formation as well as during SR image estimation efficiently. Experimental results show the effectiveness of the proposed regularization and reconstruction method for SR image.