First-principles investigation of high capacity, rechargeable CF cathode batteries based on graphdiyne and "holey" graphene carbon allotropes.

Batteries composed of CF cathodes have high theoretical specific capacities (>860 mA h g). Attempts at realizing such batteries coupled with Li anodes have failed to deliver on this promise, however, due to a discharge voltage plateau below the theoretical maximum lowering the realized energy density and difficulties with recharging the system. In this study, we use first-principles calculations to investigate novel carbon allotropes for these battery systems: graphdiyne and "holey" graphene.

The thermal instability of hydrogen-substituted graphdiyne and its role in lithium-sulfur batteries.

This study reveals the role of thermal instability in hydrogen-substituted graphdiyne (HsGDY) and its impact on lithium-sulfur (Li-S) battery performance. HsGDY undergoes significant chemical and physical transformations when subjected to thermal heating, both in the presence and absence of sulfur. Our findings suggest that the structural transformation of HsGDY into a graphene-like structure is primarily responsible for enhancing sulfur trapping and reducing the polysulfide shuttle effect, rather than the previously hypothesized alkyne-sulfur chemical interactions.

Use of Hydrogel Electrolyte in Zn-MnO Rechargeable Batteries: Characterization of Safety, Performance, and Cu Ion Diffusion.

Achieving commercially acceptable Zn-MnO rechargeable batteries depends on the reversibility of active zinc and manganese materials, and avoiding side reactions during the second electron reaction of MnO. Typically, liquid electrolytes such as potassium hydroxide (KOH) are used for Zn-MnO rechargeable batteries. However, it is known that using liquid electrolytes causes the formation of electrochemically inactive materials, such as precipitation MnO or ZnMnO resulting from the uncontrollable reaction of Mn dissolved species with zincate ions.

Room-Temperature Pseudo-Solid-State Iron Fluoride Conversion Battery with High Ionic Conductivity.

Li-metal batteries (LMBs) employing conversion cathode materials (e.g., FeF) are a promising way to prepare inexpensive, environmentally friendly batteries with high energy density.

The Role of Electrolyte Composition in Enabling Li Metal-Iron Fluoride Full-Cell Batteries.

FeF conversion cathodes, paired with Li metal, are promising for use in next-generation secondary batteries and offer a remarkable theoretical energy density of 1947 Wh kg compared to 690 Wh kg for LiNi Mn O ; however, many successful studies on FeF cathodes are performed in cells with a large (>90-fold) excess of Li that disguises the effects of tested variables on the anode and decreases the practical energy density of the battery. Herein, it is demonstrated that for full-cell compatibility, the electrolyte must produce both a protective solid-electrolyte interphase and cathode-electrolyte interphase and that an electrolyte composed of 1:1.3:3 (m/m) LiFSI, 1,2-dimethoxyethane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether fulfills both these requirements.

Thin Film Electrodes for Anodic Stripping Voltammetry: A Mini-Review.

Anodic stripping voltammetry (ASV) is a powerful electrochemical analytical technique that allows for the detection and quantification of a variety of metal ion species at very low concentrations in aqueous media. While early, traditional ASV measurements relied on macroscopic electrodes like Hg drop electrodes to provide surfaces suitable for plating/stripping, more recent work on the technique has replaced these electrodes with thin film metal electrodes generated . Such electrodes are plated alongside the analyte species onto the surface of a primary electrode, producing a composite metal electrode from which the analyte(s) can then be stripped, identified, and quantified.

Anodized Nickel Foam for Oxygen Evolution Reaction in Fe-Free and Unpurified Alkaline Electrolytes at High Current Densities.

To achieve practically high electrocatalytic performance for the oxygen evolution reaction (OER), the active surface area should be maximized without severely compromising electron and mass transport throughout the catalyst electrode. Though the importance of electron and mass transport has been studied using low surface area catalysts under low current densities (∼tens of mA/cm), the transport properties of large surface area catalysts under high operating current densities (∼500 mA/cm) for practical OER catalysis have rarely been explored. Herein, three-dimensional (3D) hierarchically porous anodized nickel foams (ANFs) with large and variable surface areas were synthesized electrochemical anodization of 3D nickel foam and applied as OER electrocatalysts in Fe-free and unpurified KOH electrolytes.

Effect of Selenium Content on Nickel Sulfoselenide-Derived Nickel (Oxy)hydroxide Electrocatalysts for Water Oxidation.

An efficient and inexpensive electrocatalyst for the oxygen evolution reaction (OER) must be found in order to improve the viability of hydrogen fuel production water electrolysis. Recent work has indicated that nickel chalcogenide materials show promise as electrocatalysts for this reaction and that their performance can be further enhanced with the generation of ternary, bimetallic chalcogenides (., NiMX); however, relatively few studies have investigated ternary chalcogenides created through the addition of a second chalcogen (.

Spatially Controlled Molecular Analysis of Biological Samples Using Nanodroplet Arrays and Direct Droplet Aspiration.

Mass spectrometry (MS) has emerged as a valuable technology for molecular and spatial evaluation of biological samples. Ambient ionization MS techniques, in particular, allow direct analysis of tissue samples with minimal pretreatment. Here, we describe the design and optimization of an alternative ambient liquid extraction MS approach for metabolite and lipid profiling and imaging from biological samples.

Probing the Degradation Chemistry and Enhanced Stability of 2D Organolead Halide Perovskites.

Recent work on quasi-2D Ruddlesden-Popper phase organolead halide perovskites has shown that they possess many interesting optical and physical properties. Most notably, they are significantly more stable when exposed to moisture when compared to the typical 3D perovskite methylammonium lead iodide (MAPI); direct evidence for the chemical source of this stability remains elusive, however. Here, we present a detailed study of the superior moisture stability of a quasi-2D Ruddlesden-Popper perovskite, -butylammonium methylammonium lead iodide (nBA-MAPI), compared to that of MAPI, and examine a simple, yet efficient, methodology to improve the stability of MAPI devices through the application of a thin layer of nBA-MAPI to the surface.

Carbon Nitride Transforms into a High Lithium Storage Capacity Nitrogen-Rich Carbon.

We describe here the metal-templated transformation of carbon nitride (CN) into nitrogen-containing carbons as anodes for Li-ion batteries (LIBs). Changing the template from the carbon- and nitrogen-immiscible Cu powder to the carbon- and nitrogen-miscible Fe powder yields different carbons; while Fe templating produces graphitized carbons of low (<10%) nitrogen content and moderate pore volume, Cu templating yields high defect-density carbons of high (32-24%) nitrogen content and larger pore volume. The Li storage capacity of the high nitrogen content and larger pore volume Cu-templated carbons exceeds that of the more graphitic Fe-templated carbons due to added contribution from Li insertion/extraction from pores and defects and to reversible faradaic Li reaction with nitrogen atoms.

Interface Engineering and its Effect on WO-Based Photoanode and Tandem Cell.

During photoelectrochemical (PEC) water splitting, the reactions occur on the surface of the photoelectrode. Therefore, the properties of the interfaces between the various components of the electrode (semiconductor/semiconductor, semiconductor/catalyst, or photoelectrode/electrolyte) affect the PEC performance of the composite material. Notably, surface trap states may hinder charge transfer and transport properties, and also cause Fermi pinning, affecting the quasi-Fermi level and onset potential under illumination, which may in turn influence the PEC performance of the corresponding tandem cells.

Highly Efficient Photoelectrochemical Water Splitting from Hierarchical WO/BiVO Nanoporous Sphere Arrays.

Nanoarchitecture of bismuth vanadate (BiVO) photoanodes for effectively increasing light harvesting efficiency and simultaneously achieving high charge separation efficiency is the key to approaching their theoretic performance of solar-driven water splitting. Here, we developed hierarchical BiVO nanoporous sphere arrays, which are composed of small nanoparticles and sufficient voids for offering high capability of charge separation. Significantly, multiple light scattering in the sphere arrays and voids along with the large effective thickness of the BiVO photoanode induce efficient light harvesting.

Activation of a Nickel-Based Oxygen Evolution Reaction Catalyst on a Hematite Photoanode via Incorporation of Cerium for Photoelectrochemical Water Oxidation.

There has been debate on whether Ni(OH) is truly catalytically active for the photo/electrocatalytic oxygen evolution reaction. In this report, we synthesized a Ni(OH) cocatalyst on a hematite photoanode and showed that, as has been proposed in other studies, the current density varies as a function of scan rate, which arises due to a photoinduced capacitive charging effect. We discovered that this photoinduced charging of Ni can be overcome by mixing cerium nitrate into the Ni precursor solution.