ZnO@Bi5O7I Heterojunction Derived from ZIF-8@BiOI for Enhanced Photocatalytic Activity under Visible Light

In the study, ZIF-8@BIOI composites were synthesized by the hydrothermal method and then calcined to acquire the ZnO@Bi5O7I composite as a novel composite for the photocatalytic deterioration of the antibiotic tetracycline (TC). The prepared ZnO@Bi5O7I composites were physically and chemically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmet–Teller (BET) surface area, UV–Vis diffuse reflectance spectroscopy (DRS), emission fluorescence spectra, transient photocurrent response, electrochemical impedance spectra and Mott–Schottky. Among the composites formed an n–n heterojunction, which increased the separation efficiency of electrons and holes and the efficiency of charge transfer. After the photocatalytic degradation test of TC, it showed that ZnO@Bi5O7I (2:1) had the best photodegradation effect with an 86.2% removal rate, which provides a new approach to the treatment of antibiotics such as TC in wastewater.

Analysis of MEA’s durability under Accelerated Stress Tests that mimic realistic automotive operations

This work aims at studying MEA’s ageing under single operational “mode” accelerated stress tests (AST), that were specifically designed to replicate under hydrogen/air feeding the main stressors of realistic operations in the automotive sector. A methodology for developing AST is here presented and preliminary results about the activity included. In particular, low power and high power functioning have been mimicked in a Zero-Gradient hardware, which allows a reliable materials comparison. Quantities, measurable in-situ and operando, have been tracked during ageing, like cell power, polarization curves, Pt active area, oxygen mass transport resistance, Electrochemical Impedance Spectra. The final objective is to clarify the underlying ageing mechanisms and assess the contribution of each specific operation to the MEA lifetime, focusing in particular on the cathode catalyst layer durability. Moreover, the rate of voltage loss for the new ASTs has been successfully correlated to the degradation observed under a complete driving cycle protocol.

Battery State Estimation with ANN and SVR Evaluating Electrochemical Impedance Spectra Generalizing DC Currents

The demand for energy storage is increasing massively due to the electrification of transport and the expansion of renewable energies. Current battery technologies cannot satisfy this growing demand as they are difficult to recycle, as the necessary raw materials are mined under precarious conditions, and as the energy density is insufficient. Metal–air batteries offer a high energy density as there is only one active mass inside the cell and the cathodic reaction uses the ambient air. Various metals can be used, but zinc is very promising due to its disposability and non-toxic behavior, and as operation as a secondary cell is possible. Typical characteristics of zinc–air batteries are flat charge and discharge curves. On the one hand, this is an advantage for the subsequent power electronics, which can be optimized for smaller and constant voltage ranges. On the other hand, the state determination of the system becomes more complex, as the voltage level is not sufficient to determine the state of the battery. In this context, electrochemical impedance spectroscopy is a promising candidate as the resulting impedance spectra depend on the state of charge, working point, state of aging, and temperature. Previous approaches require a fixed operating state of the cell while impedance measurements are being performed. In this publication, electrochemical impedance spectroscopy is therefore combined with various machine learning techniques to also determine successfully the state of charge during charging of the cell at non-fixed charging currents.

Impedance Spectroscopy Measurements of Ionomer Film Oxygen Transport Resistivity in Operating Low-Pt PEM Fuel Cell

The work presents a model for local impedance of low-Pt proton exchange membrane fuel cells (PEMFCs), including cathode pore size distribution and O2 transport along pores and through a thin ionomer film covering Pt/C agglomerates. The model was applied to fit the local impedance spectra of low-Pt fuel cells operated at current densities from 100 to 800 mA cm−2 and recorded by a segmented cell system. Assuming an ionomer film thickness of 10 nm, the fitting returned the product of the dimensionless Henry’s constant of oxygen dissolution in ionomer KH by the oxygen diffusivity DN in the ionomer (KHDN). This parameter allowed us to determine the fundamental O2 transport resistivity RN through the ionomer film in the working electrode under conditions relevant to the realistic operation of PEMFCs. The results show that variation of the operating current density does not affect RN, which remains nearly constant at ≃0.4 s cm−1.

Melanin’s Semiconductor Nature and His Polymer Structure Successfully Modifies Sulfur Cathode and Increases Efficiency on Li-S Batteries

Dynamics of change in impedance spectra and electrochemical parameters of the Li-S rechargeable batteries with non-aqueous liquid electrolyte 0.7 M LiIm, 0.25 M LiNO3, DME: DOL (2:1) during storage after assembly and cycling have been shown. For modification of the Sulfur cathode, we used the different types of melanin. Our results confirm that melanin can be used as a promising component of sulfur-based electrodes

Experimental validation of axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency

The axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency capability have been proposed by adjusting the external electric resistance and the ratio of piezoelectric layer numbers between the actuator part and the sensor part, which have promising potential in designing the novel cymbal transducer for underwater sound projector and ultrasonic radiator applications. In the previous studies, the multilayer models were established to guide the design of the transducers with arbitrary layer number, and analyzed the dynamic characteristics theoretically. In this work, an experimental study is performed to validate the theoretical models and predictions. Piezoelectric rings with multiple concentric annular electrodes are designed to characterize the multilayer piezoelectric composite cylindrical transducers. The top surface of the piezoelectric rings is divided into two separate parts. One part is covered by multiple concentric annular electrodes, corresponding to the piezoelectric layers, and the other part is uncovered, corresponding to the elastic layers. Four prototypes are fabricated and each consists of four concentric annular electrodes. The impedance spectra are measured by the impedance analyzer to obtain the resonance and anti-resonance frequencies. Effects of two adjusting methods on the dynamic characteristics are evaluated experimentally. The experimental results basically coincide with the theoretical ones. This comprehensive experimental work assures the feasibility of using axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequencies and confirms the benefit of the developed theoretical models for guiding the fabrication and optimization of this type of transducers.

Experimental Study on the Corrosion of Carbon Steel and Aluminum Alloy in Firefighting Protein Foam Concentrates

The corrosion of mild steel and Al alloy in Fomtec P 6% and 6% P Profoam 806 protein-based foam concentrates was investigated. Weight-loss data for steel showed corrosion penetration of 0.745 mipy in Fomtec and 2.269 mipy in Profoam, whereas for Al alloy the penetration levels were 0.474 and 1.093 mipy, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy allowed characterization of the metallic surface covered or free from corrosion products. Values of corrosion potential, corrosion current density and corrosion penetration were calculated by using potentiodynamic polarization curves. Electrochemical impedance spectra illustrated the change in polarization resistance during anodic polarization. Data obtained by accelerated electrochemical methods confirm the greater aggressiveness of the Profoam concentrate compared to Fomtec concentrate.

One-Step Electrodeposition of Superhydrophobic Coating on 316L Stainless Steel

Superhydrophobic coatings were fabricated through a one-step electrochemical process onto the surface of 316L stainless steel samples. The presence of hierarchical structures at micro/nanoscale and manganese stearate into the coatings gave superhydrophobicity to the coating, with contact angle of ~160°, and self-cleaning ability. Corrosion resistance of 316L samples was also assessed also after the electrodeposition process through Electrochemical Impedance Spectra recorded in an aqueous solution mimicking seawater condition.

An Impedance Study of the Membrane Polarisation Effect in Simulated Rock Systems

<p>Work is reported on the development of a high precision, low frequency impedance bridge, and the use of impedance measurement in characterising the induced polarisation effect of unmineralised material. Impedance spectra for a variety of laboratory model clay/rock/electrolyte systems are analysed in terms of an equivalent circuit. By measuring the dependence of the parameters of this circuit, on such variables as electrolyte type and concentration, temperature and pore geometry, an electrochemical model for membrane polarisation has been developed. Polarisation is considered to arise from diffusional limitation of cations at the membrane/electrolyte interface of clay aggregations in rock pores, and this is found to be amenable to a Warburg diffusional impedance analysis.</p>

A Study of the Frequency Domain Induced Polarisation Effects Displayed by Clay and by Cation Exchange Resin, Model Soil Systems

<p>Work is reported of the development of clay and resin model soil systems for the observation of induced polarisation phenomena. A measuring technique is developed to determine impedance spectra of such models over the frequency range of 10-3 to 10 4 Hz, and a variety of model cells tested varying such parameters as temperature, electrolyte type and concentration, and bead size of resin. An increase in impedance with decrease in frequency is observed, consistent with field observation of the induced polarisation phenomenon associated with moist, non-mineralised soils, and a number of empirical observations of the form of this are made.</p>