Perspective—Electrochemistry in Understanding and Designing Electrochemical Energy Storage Systems

The number of publications in electrochemical energy storage has increased exponentially in the past decades, focusing mostly on materials science. The electrochemical process controlling the observed overall performances is often not well discussed. This article highlights the importance of understanding rate-limiting steps in the electrochemical process which change dynamically at different conditions and scales. Applying electrochemistry to identify and overcome those rate-limiting steps in the electrochemical devices is the pre-requisite to discover effective solutions and design different batteries to further advance electrochemical energy storage systems for a broad range of various applications.

High Activity and Selectivity of M-N/C Catalysts toward Two-Electron O2 Electroreduction

Hydrogen Peroxide (H2O2) is a versatile and environmentally friendly chemical oxidant with a remarkably diverse range of applications, including fine chemical synthesis, first aid kits for disinfection, pulp and textile bleaching, wastewater treatment and others. Industrial production of H2O2 is based on the anthraquinone oxidation/reduction process, which consumes a lot of energy, requires complex and large-scale equipment, and mass extraction solvents, generating an enormous waste. There is a general demand for a more decentralised infrastructure, where energy conversion and chemical synthesis are conducted closer to the point of consumption. In this context, developing an electrochemical process to partially reduce O2 to H2O2 (O2 + 2H+/e- → H2O2) in an acidic medium would be an attractive strategy that could be carried out under ambient conditions using renewable energies. However, practical and economic electrocatalysts that exhibit high activity and selectivity for hydrogen peroxide production is to be developed. A series of M-N/C catalysts (M = Fe, Co, and Cu) were prepared in the present study. The performance (activity and selectivity) of these catalysts for the oxygen reduction reaction was investigated in the potential window of 0.2 V to 1.0 V vs. the Reversible Hydrogen Electrode (RHE). Electrochemical measurements demonstrated that the Co-N/C [c] electrocatalyst exhibits high ORR activity and exceptional selectivity for hydrogen peroxide production (92% at 0.5 V vs. RHE).

Facile Synthesis of the Dicyanophosphide Anion via Electrochemical Activation of White Phosphorus: An Avenue to Organophosphorus Compounds

Organophosphorus compounds (OPCs) have gained tremendous interest in the past decades due to their wide applications ranging from synthetic chemistry to materials and biological sciences. We describe herein a practical and versatile approach for the transformation of white phosphorus (P4) into useful OPCs with high P atom economy via a key bridging anion [P(CN)2]–. This anion can be prepared on a gram scale directly from P4 through an unprecedented electrochemical process. A variety of OPCs involving phosphinidenes, cyclophosphanes and phospholides have been made readily accessible from P4 in a two-step manner. Our approach has a significant impact on the future preparation of OPCs in laboratory and industrial settings.

Electrochemical Measurement System for Chlorides in Drinking and Wastewater

This paper presents a system for the measurement of chlorides in drinking and wastewater, based on an electrochemical process using a selective electrode as a transducer, which was developed by this group. The measurement for the concentration is carried out by introducing the implemented electrode (considered as reference) in the sample that will be analyzed; then a current is passed producing a potential difference in the system. Different aqueous solutions of sodium chloride (NaCl) were used, ranging between 35 and 3546 µg of chloride ions (Cl−). As a data acquisition and monitoring system for the analysis, an ATmega 328P microcontroller was used as the main capture element for subsequent interpretation through graphics. The experimental results show that it was possible to detect a potential difference in the electrochemical measurement system that corresponded to 35 µg of chloride ions (Cl−), making clear the detection process and the selectivity of chloride ions. It is important to mention that with this measurement system and the applied methodology, results are obtained in real time using a small sample volume and without generate ng extra liquid waste, compared to the application of the traditional analytical titrimetric method. Finally, this chloride measurement system is inexpensive and can be used in drinking and wastewater measurements.

Nanoimprinted and Anodized Templates for Large-Scale and Low-Cost Nanopatterning

Nanopatterning to fabricate advanced nanostructured materials is a widely employed technology in a broad spectrum of applications going from spintronics and nanoelectronics to nanophotonics. This work reports on an easy route for nanopatterning making use of ordered porous templates with geometries ranging from straight lines to square, triangular or rhombohedral lattices, to be employed for the designed growth of sputtered materials with engineered properties. The procedure is based on large-scale nanoimprinting using patterned low-cost commercial disks, as 1-D grating stamps, followed by a single electrochemical process that allows one to obtain 1-D ordered porous anodic templates. Multiple imprinting steps at different angles enable more complex 2-D patterned templates. Subsequently, sputtering facilitates the growth of ferromagnetic antidot thin films (e.g., from 20 to 100 nm Co thick layers) with designed symmetries. This technique constitutes a non-expensive method for massive mold production and pattern generation avoiding standard lithographical techniques. In addition, it overcomes current challenges of the two-stage electrochemical porous anodic alumina templates: (i) allowing the patterning of large areas with high ordering and/or complex antidot geometries, and (ii) being less-time consuming.