Recent advancements in supercapacitor technology

Solid-state batteries (SSBs) using a solid electrolyte show potential for providing improved safety as well as higher energy and power density compared with conventional Li-ion batteries. However, two critical bottlenecks remain: the development of solid electrolytes with ionic conductivities comparable to or higher than those of conventional liquid electrolytes and the creation of stable interfaces between SSB components, including the active material, solid electrolyte and conductive additives. Although the first goal has been achieved in several solid ionic conductors, the high impedance at various solid/solid interfaces remains a challenge. Recently, computational models based on ab initio calculations have successfully predicted the stability of solid electrolytes in various systems. In addition, a large amount of experimental data has been accumulated for different interfaces in SSBs. In this Review, we summarize the experimental findings for various classes of solid electrolytes and relate them to computational predictions, with the aim of providing a deeper understanding of the interfacial reactions and insight for the future design and engineering of interfaces in SSBs. We find that, in general, the electrochemical stability and interfacial reaction products can be captured with a small set of chemical and physical principles. The reliable operation of solid-state batteries requires stable or passivating interfaces between solid components. In this Review, we discuss models for interfacial reactions and relate the predictions to experimental findings, aiming to provide a deeper understanding of interface stability.

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Understanding interface stability in solid-state batteries

Defect and Interface Engineering for Aqueous Electrocatalytic CO2 Reduction

The appeal and promise of synthetic organic electrochemistry have been appreciated over the past century. In terms of redox chemistry, which is frequently encountered when forging new bonds, it is difficult to conceive of a more economical way to add or remove electrons than electrochemistry. Indeed, many of the largest industrial synthetic chemical processes are achieved in a practical way using electrons as a reagent. Why then, after so many years of the documented benefits of electrochemistry, is it not more widely embraced by mainstream practitioners? Erroneous perceptions that electrochemistry is a "black box" combined with a lack of intuitive and inexpensive standardized equipment likely contributed to this stagnation in interest within the synthetic organic community. This barrier to entry is magnified by the fact that many redox processes can already be accomplished using simple chemical reagents even if they are less atom-economic. Time has proven that sustainability and economics are not strong enough driving forces for the adoption of electrochemical techniques within the broader community. Indeed, like many synthetic organic chemists that have dabbled in this age-old technique, our first foray into this area was not by choice but rather through sheer necessity. The unique reactivity benefits of this old redox-modulating technique must therefore be highlighted and leveraged in order to draw organic chemists into the field. Enabling new bonds to be forged with higher levels of chemo- and regioselectivity will likely accomplish this goal. In doing so, it is envisioned that widespread adoption of electrochemistry will go beyond supplanting unsustainable reagents in mundane redox reactions to the development of exciting reactivity paradigms that enable heretofore unimagined retrosynthetic pathways. Whereas the rigorous physical organic chemical principles of electroorganic synthesis have been reviewed elsewhere, it is often the case that such summaries leave out the pragmatic aspects of designing, optimizing, and scaling up preparative electrochemical reactions. Taken together, the task of setting up an electrochemical reaction, much less inventing a new one, can be vexing for even seasoned organic chemists. This Account therefore features a unique format that focuses on addressing this exact issue within the context of our own studies. The graphically rich presentation style pinpoints basic concepts, typical challenges, and key insights for those "electro-curious" chemists who seek to rapidly explore the power of electrochemistry in their research.

A Survival Guide for the "Electro-curious".

The severe limitations of fossil fuels and finite resources influence the scientific community to reconsider chemical synthesis and establish sustainable techniques. Several promising methods have emerged, and electro-organic conversion has attracted particular attention from international academia and industry as an environmentally benign and cost-effective technique. The easy application, precise control, and safe conversion of substrates with intermediates only accessible by this method reveal novel pathways in synthetic organic chemistry. The popularity of electricity as a reagent is accompanied by the feasible conversion of bio-based feedstocks to limit the carbon footprint. Several milestones have been achieved in electro-organic conversion at rapid frequency, which have opened up various perspectives for forthcoming processes.

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Electro-organic synthesis – a 21st century technique

Despite the growing popularity of cyclic voltammetry, many students do not receive formalized training in this technique as part of their coursework. Confronted with self-instruction, students can be left wondering where to start. Here, a short introduction to cyclic voltammetry is provided to help the reader with data acquisition and interpretation. Tips and common pitfalls are provided, and the reader is encouraged to apply what is learned in short, simple training modules provided in the Supporting Information. Armed with the basics, the motivated aspiring electrochemist will find existing resources more accessible and will progress much faster in the understanding of cyclic voltammetry.

A Practical Beginner’s Guide to Cyclic Voltammetry

Ligand exchange reactions are commonly used to alter the surface chemistry of metal chalcogenide quantum dots; however, a lack of quantifiable data for these processes limits the rational functionalization of nanomaterials. Here, we quantify the X-type ligand exchange reaction between carboxylate-terminated ligands on PbS quantum dots via1H NMR spectroscopy. Using spectroscopic handles of both the native and exchange ligand, bound and free forms of each have been quantified as a function of exchange ligand concentration. We find that the equilibrium constants for the reaction between oleate-capped PbS quantum dots and undec-10-enoic acid are 2.23 ± 0.50 and 2.14 ± 0.42 for sets of nanocrystals prepared by two different synthetic methods. X-ray photoelectron, absorbance, and emission spectroscopies indicate that the carboxylate exchange reaction does not alter the lead ion coverage of the nanocrystal surface. The quantitative equilibrium constant determined herein can be used to improve control over partial ligand exchange reactions on PbS nanocrystals.

Exchange equilibria of carboxylate-terminated ligands at PbS nanocrystal surfaces

Initial Benchmarks of UV LEDs and Comparisons with White LEDs

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Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products

Air quality monitoring is a rapidly growing area of citizen science, or community science (CS), thanks to the availability of low-cost sensors. Contributing to a crowdsourced data platform (e.g., http:// purpleair .com/ map) is usually easy in urban areas, where there is access to uninterrupted electricity and wireless internet (Wi-Fi). However, there are sometimes security restrictions on Wi-Fi or a lack of exterior power outlets. Also, rural regions, particularly in low- and middle-income countries, often lack electricity and Wi-Fi continuity. RTI International has designed and distributed a solar power and Wi-Fi station that can adequately power both a small air quality sensor (e.g., PurpleAir PA-II) and a Wi-Fi hotspot to overcome these challenges. The station housing can accommodate a battery, a controller, and a cell phone or another type of Wi-Fi hotspot device. This paper discusses the need for such a station; a design for the current station, including parts list; suggestions for modifications in various use cases; and design factors to consider, including amount of sunlight per day, intended number of operational days under cloudy conditions, season, and total power requirements. This method is intended to be open source and a starting point for citizen scientists and CS projects.

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Kelley J. Rountree

Papers

A Practical Beginner’s Guide to Cyclic Voltammetry

Exchange equilibria of carboxylate-terminated ligands at PbS nanocrystal surfaces

Initial Benchmarks of UV LEDs and Comparisons with White LEDs

Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products

Solar Station for an Off-the-Grid Air Quality Sensor System