Ultrafine TaOx/CB Oxygen Reduction Electrocatalyst Operating in Both Acidic and Alkaline Media

The high activity of non-platinum electrocatalysts for oxygen reduction reaction (ORR) in alkaline media is necessary for applications in energy conversion devices such as fuel cells and metal-air batteries. Herein, we present the electrocatalytic activity of TaOx/carbon black (CB) nanoparticles for the ORR in an alkaline atmosphere as well as in an acidic electrolyte. Ultrafine TaOx nanoparticles 1–2 nm in size and uniformly dispersed on CB supports were prepared by potentiostatic electrodeposition in a nonaqueous electrolyte and subsequent annealing treatment in an H2 flow. The TaOx/CB nanoparticles largely catalyzed the ORR with an onset potential of 1.03 VRHE in an O2-saturated 0.1 M KOH solution comparable to that of a commercial Pt/CB catalyst. ORR activity was also observed in 0.1 M H2SO4 solution. According to the rotating ring disk electrode measurement results, the oxide nanoparticles partly produced H2O2 during the ORR in 0.1 M KOH, and the ORR process was dominated by both the two- and four-electron reductions of oxygen in a diffusion-limited potential region. The Tafel slope of −120 mV dec−1 in low and high current densities revealed the surface stability of the oxide nanoparticles during the ORR. Therefore, these results demonstrated that the TaOx/CB nanoparticles were electroactive for the ORR in both acidic and alkaline electrolytes.

Electrodeposition of Ni–Fe alloy from solutions based on deep eutectic solvent ethaline

The kinetics of сodeposition of nickel and iron in an electrolyte based on a deep eutectic solvent (ethaline) was studied by voltammetry method. It was established that the partial voltammograms of iron ions reduction during alloy electrodeposition correspond to the region of electrode potentials, which is more than 100 mV positive in comparison with the electrodeposition potentials of pure iron. It was shown that the acceleration of iron ion electroreduction is associated with the gain in energy due to the alloy formation and a decrease in the overvoltage of iron electrodeposition during alloying. The change in the kinetics of iron electrodeposition can be explained by both a change in the mechanism of its electrodeposition in conjunction with nickel and a change in the state of the electrode surface in the potential region of the alloy formation. Comparison between the ratio of the content of the alloy components in the metal and the corresponding ions in the electrolyte showed that nickel and iron electrodeposit into the alloy in quantities that are proportional to their content in the electrolyte. Thus, electrodeposition of nickel-iron alloy from ethaline with a water content of up to 3% occurs by the so-called normal mechanism.

Current calculation of irreversible electrode reaction mechanismsin linear sweep voltammetry

Application of exponential infinite series gives highly accurate analytical solution contributing to the theory of linear sweep voltammetry for single scan experiments. We have calculated theoretical dimensionless current function (usually denoted as π1/2χ(bt)) at relevant potentials for irreversible charge transfer without a coupled chemical reaction. For this purpose several transformation techniques were used, which convert the derived infinite series into summable sequences. Since infinite series of further electrochemical mechanisms with irreversible electrode reaction have similar features (particularly those comprising preceding and catalytic chemical reaction), the same approach can be successfully applied also for further electrochemical mechanisms. The respective infinite series are divergent in the most important potential region at and after voltammetric peak therefore their transformation by Epsilon and Levin transform techniques was used. Necessary arbitrary precision arithmetic (APA) was implemented by UBASIC. The results were compared to the customary solution of Nicholson and Shain, who computed the current-potential curves by means of numerical solution of the integral equations but with a much lower precision. Our results were obtained in a broad potential range including the potential regions where the series are divergent. Obtained current functions are precise to 12 valid decimal numbers, which is utilizable for evaluation of the results achieved by various faster but less precise digital simulation techniques.

Determination of groundwater potential distribution of Ceylanpinar plain (Turkey) in Upper Mesopotamia by using geographical information techniques and Fuzzy-AHP with MCDM

The Ceylanpinar Plain is an important part of Upper Mesopotamia and one of the largest plains of Turkey, is in danger of facing water scarcity due to global climate change. For this reason, the potential of Groundwater Resources is important. In this study, groundwater potential zones in the Ceylanpinar Plain basin were investigated utilizing a weighted overlay analysis method combined with fuzzy Analytical Hierarchy Process (FAHP) multi-criteria decision-making (MCDM) approaches and geoinformation technologies. The groundwater potential zone map was created using ten theme layers that were produced and processed in a GIS environment (GPZM). After that, possible groundwater zones were identified and classified into five categories: very good, good, medium, poor, and very poor. By assessing the present open well distribution and yield data of selected wells within the research catchment, the predicted GWPZ (groundwater potential zones) was confirmed. As a result, 17% of the study area was found to be very good, 39% good, 20% moderate, 21.4% poor and 2.6% very poor. This study provides a key estimate and crucial information for regional water administrators and officials in southeast Turkey by giving a map of the groundwater potential region, in order to ensure sustainable groundwater management.

Pitting corrosion prediction from cathodic data: application of machine learning

Purpose To constitute input data, the authors carried out electrochemical experiments. The authors performed voltammetric scans in a very cathodic potential region. The authors constituted an experimental table where for each experiment we note the current values recorded at a low polarization range and the pitting potential observed in the anodic region. This study aims to concern carbon steel used in a nuclear installation. The properties of the chemical solutions are close to that of the cooling fluid used in the circuit. Design/methodology/approach In a previous study, this paper demonstrated the effectiveness of machine learning in predicting the localized corrosion resistance of a material by considering as input data the physicochemical properties of its environment (Boucherit et al., 2019). With the present study, the authors improve the results by considering as input data, cathodic currents. The reason of such an approach is to have input data that integrate both the surface state of the material and the physicochemical properties of its environment. Findings The experimental table was submitted to two neural networks, namely, a recurrent network and a convolution network. The convolution network gives better pitting potential predictions. Results also prove that the prediction by observing cathodic currents is better than that obtained by considering the physicochemical properties of the solution. Originality/value The originality of the study lies in the use of cathodic currents as input data. These data contain implicit information on both the chemical environment of the material and its surface condition. This approach appears to be more efficient than considering the chemical composition of the solution as input data. The objective of this study remains, at the same time, to seek the optimal neuronal architectures and the best input data.

The eikonal approach to gravitational scattering and radiation at $$ \mathcal{O} $$(G3)

Using $$ \mathcal{N} $$ N = 8 supergravity as a theoretical laboratory, we extract the 3PM gravitational eikonal for two colliding massive scalars from the classical limit of the corresponding elastic two-loop amplitude. We employ the eikonal phase to obtain the physical deflection angle and to show how its non-relativistic (NR) and ultra-relativistic (UR) regimes are smoothly connected. Such a smooth interpolation rests on keeping contributions to the loop integrals originating from the full soft region, rather than restricting it to its potential sub-region. This task is efficiently carried out by using the method of differential equations with complete near-static boundary conditions. In contrast to the potential-region result, the physical deflection angle includes radiation-reaction contributions that are essential for recovering the finite and universal UR limit implied by general analyticity and crossing arguments. We finally discuss the real emission of massless states, which accounts for the imaginary part of the 3PM eikonal and for the dissipation of energy-momentum. Adopting a direct approach based on unitarity and on the classical limit of the inelastic tree-level amplitude, we are able to treat $$ \mathcal{N} $$ N = 8 and General Relativity on the same footing, and to complete the conservative 3PM eikonal in Einstein’s gravity by the addition of the radiation-reaction contribution. We also show how this approach can be used to compute waveforms, as well as the differential and integrated spectra, for the different radiated massless fields.

Decrease in Pitting Corrosion Resistance of Extra-High-Purity Type 316 Stainless-Steel by Cu2+ in NaCl

The effect of Cu2+ in bulk solution on pitting corrosion resistance of extra-high-purity type 316 stainless-steel was investigated. Pitting occurred in 0.1 M NaCl-1 mM CuCl2, whereas pitting was not initiated in 0.1 M NaCl. Although deposition of Cu2+ on the surface occurred regardless of a potential region in 0.1 M NaCl-1 mM CuCl2, Cu2+ in bulk solution had no influence on the passive film formation. The decrease in pitting corrosion resistance in 0.1 M NaCl-1 mM CuCl2 resulted from the deposited Cu or Cu compound and continuous supply of Cu2+ on the surface.

Plasma injections arising out of dynamic ionosphere

<p>We propose ionospheric plasma injections to the magnetosphere (ionospheric injection) as a new plasma process in the polar ionosphere. The ionospheric injection is first triggered by westward electric fields transmitted from the convection surge in the magnetosphere in association with dipolarization onset. Localized westward electric fields yield electrostatic potential in the ionosphere as a result of differing electron and ion mobility in the E-layer. To ensure quasi-neutrality of ionospheric plasmas, excess charges are released as injections out of the ionosphere, specifically electrons from positive potential region in higher latitudes and ions from negative potentials in lower latitudes. Potential difference on the order of 10 kV in north-south directions produces southward electric fields (100mv/m) at the footprint of the convection surge in both northern and southern hemispheres. Resultant geomagnetic field lines are not in equipotential equilibrium during ionospheric injections but instead develop downward electric fields in positive potential regions in higher latitudes to extract electrons and upward electric fields in negative potential regions in lower latitudes to extract ions. Parallel electric fields can exist in the magnetic mirror geometry of auroral field lines if the magnetospheric plasma follows quasi-neutral equilibrium. Because ionospheric injection has inherent dynamo processes as well as load, we term the polar ionosphere “dynamic ionosphere”.</p><p>Cold plasmas injected out of the dynamic ionosphere are transported along the dynamical trajectories to the magnetosphere conserving the total energy (including electrostatic potentials) and first adiabatic invariant. Electrons/ions traveling in downward/upward electric fields lose perpendicular and lower velocities in parallel component, leaving only the energetic part of ionospheric plasmas collimated along the field lines. Steady-state and one-dimensional dynamical trajectory shows that ion and electron temperatures at the ionosphere initially at 1 eV increased parallel temperatures to 202 eV and decreased perpendicular temperatures to 0.001 eV at geosynchronous altitudes where the electrostatic potential difference between ionosphere and magnetosphere was assumed to be 200 V. When potential difference increased to 600 V, the parallel temperatures increased to 602 eV, while perpendicular temperatures remain unchanged. Parallel potentials preferentially heated the ionospheric cold plasmas in parallel directions and transported tailward to feed the magnetosphere.</p>

Understanding the zinc discharge from sodium sulphate solution in the presence of surfactants

This paper aims to understand the effect of surfactants on zinc discharge in sulphate solutions on a solid electrode and to collect new experimental data that would give a deeper insight into the processes involved in industrial electrolysis. Anionic and cationic coagulants (flocculants) and an anionic frother were used as surfactants. Electrolysis was conducted in the potential region of –1050 to –1250 mV (Ag/АgCl) in stationary and dynamic conditions in sodium sulphate solution under intensive stirring. The authors obtained comparative data on the zinc discharge current in electrolyte with and without frother at the scan velocities of 2 to 100 mV/sec. It is noted that at higher scan velocities (>10–20 mV/sec) and in the initial electrolysis phase the zinc discharge process develops in a mixed mode. In this case, as the study showed, the positive effect of the frother on zinc discharge is most distinguished. A reaction order was designed based on zinc ion with four potentials to prove that the zinc electrowinning process develops in a mixed mode. It is shown that the addition of frother raises the reaction order from 1.2 to 1.5, which is attributed to a larger effective cathode surface area. The data obtained in a galvanostatic mode under intensive stirring conditions indicate that, at the current density of 1.7 mA/cm2, the electrode polarization is 1.6 times lower in the presence of cationic coagulant and almost 3 times lower in the presence of anionic coagulant. The data given in this paper are also indicative of a changing electrolysis mode. Under stirring, a transition is observed from a diffusion mode of zinc ion reduction to a mixed one. The experimental data obtained under intensive stirring conditions in sodium sulphate solution with frother, as well as anionic and cationic coagulants are in line with the theory of electrochemical processes.