Rechargeable organic–air redox flow batteries

A rechargeable organic–air flow battery based on aqueous electrolytes is proposed and tests are conducted in a divided cell with a three-electrode configuration. Quinoxaline is used as the negative redox couple due to its low electrode potential of c.a. −0.9 V vs. Hg|HgO in aqueous electrolytes. High-surface-area nickel mesh and manganese-dioxide electrodes were employed for oxygen evolution and reduction, respectively, together with a low-cost hydroxide doped polybenzimidazole (m-PBI) separator (c.a. 20 μm). In typical alkaline electrolytes (2 M NaOH), the open-circuit voltage of the flow battery was c.a. 0.95 V, which is comparable to existing organic-based batteries. The average charge and discharge cell voltage ranges at 5–10 mA cm−2 were 1.7–1.95 V and 0.4–0.7 V, respectively. Despite using low-cost materials, average coulombic and energy efficiencies of the batteries were c.a. 81 and 25%, respectively, at 7.5 mA cm−2 over 20 cycles

Uncertainty quantification for flow and transport in highly heterogeneous porous media based on simultaneous stochastic model dimensionality reduction

Groundwater flow models are usually subject to uncertainty as a consequence of the random representation of the conductivity field. In this paper, we use a Gaussian process model based on the simultaneous dimension reduction in the conductivity input and flow field output spaces in order quantify the uncertainty in a model describing the flow of an incompressible liquid in a random heterogeneous porous medium. We show how to significantly reduce the dimensionality of the high-dimensional input and output spaces while retaining the qualitative features of the original model, and secondly how to build a surrogate model for solving the reduced-order stochastic model. A Monte Carlo uncertainty analysis on the full-order model is used for validation of the surrogate model

The corrosion behaviour of CoCrFeNi-x (x = Cu, Al, Sn) high entropy alloy systems in chloride solution

The corrosion properties in NaCl solution of four equiatomic HEAs of the CoCrFeNi system adding Al, Cu and Sn are investigated. These alloys are processed by vacuum arc melting and assessed via the Potentiostat method. The properties were compared with two standard stainless steels. The results indicate that CoCrFeNiSn possesses the best passivation in this solution, explained by the alloy phases and presence at the surface of elements in oxidation states corresponding to stable oxide films. The other systems show a range of behaviours attributable to their different microstructures and varying potential for stable oxide formation

Pulsed current co-electrodeposition of kesterite Cu2ZnSnS4 absorber material on fluorinated tin oxide (FTO) glass under galvanostatic conditions

The film of kesterite Cu2ZnSnS4 (CZTS) was prepared on a fluorinated tin oxide (FTO) substrate by a galvanostatically pulsed electrodeposition. The effect of duty cycles on electrodeposition was investigated at 33%, 50%, and 67% duty cycle. For the characterization, the prepared films were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray spectroscopy (XRD), UV-vis spectroscopy, Raman spectroscopy, and an atomic emission elemental analyzer. According to the experiments, surface morphologies of the CZT precursor appear to be uniform with fewer pores. After sulfurization, the morphologies of CZTS film become more uniform. When considering duty cycles, a higher duty cycle resulted in the surface being denser, more compact, more uniform, and smoother. Based upon the XRD and EDS, the film's composition consists of copper, zinc, tin, and sulfur. The compound formulae is also proved to be copper zinc tin sulfide

Energy Efficiency of Electrowinning

The winning of high purity metal from aqueous solutions through electrodeposition is the final processing recovery step for many nonferrous metals. Direct electrical current/voltage provides the necessary driving force to promote the necessary reactions at an industrially relevant rate. Energy, especially electrical, is often the highest cost for electrowinning operations. Therefore, energy efficiency is a paramount concern for modern facilities. This chapter discusses electrical energy consumption in aqueous electrowinning with a specific focus on cell voltage and current efficiency. It also presents potential improvements