Inkjet Printing Infiltration of the Doped Ceria Interlayer in Commercial Anode-Supported SOFCs.

Single-step inkjet printing infiltration with doped ceria Ce0.9Ye0.1O1.95 (YDC) and cobalt oxide (CoxOy) precursor inks was performed in order to modify the properties of the doped ceria interlayer in commercial (50 × 50 × 0.5 mm3 size) anode-supported SOFCs. The penetration of the inks throughout the La0.8Sr0.2Co0.5Fe0.5O3-δ porous cathode to the Gd0.1Ce0.9O2 (GDC) interlayer was achieved by optimisation of the inks' rheology jetting parameters. The low-temperature calcination (750 °C) resulted in densification of the Gd-doped ceria porous interlayer as well as decoration of the cathode scaffold with nanoparticles (~20-50 nm in size). The I-V testing in pure hydrogen showed a maximum power density gain of ~20% at 700 °C and ~97% at 800 °C for the infiltrated cells. The latter effect was largely assigned to the improvement in the interfacial Ohmic resistance due to the densification of the interlayer. The EIS study of the polarisation losses of the reference and infiltrated cells revealed a reduction in the activation polarisations losses at 700 °C due to the nano-decoration of the La0.8Sr0.2Co0.5Fe0.5O3-δ scaffold surface. Such was not the case at 800 °C, where the drop in Ohmic losses was dominant. This work demonstrated that single-step inkjet printing infiltration, a non-disruptive, low-cost technique, can produce significant and scalable performance enhancements in commercial anode-supported SOFCs.

Iron Selenide Microcapsules as Universal Conversion-Typed Anodes for Alkali Metal-Ion Batteries.

Rechargeable alkali metal-ion batteries (AMIBs) are receiving significant attention owing to their high energy density and low weight. The performance of AMIBs is highly dependent on the electrode materials. It is, therefore, quite crucial to explore suitable electrode materials that can fulfil the future requirements of AMIBs. Herein, a hierarchical hybrid yolk-shell structure of carbon-coated iron selenide microcapsules (FeSe2 @C-3 MCs) is prepared via facile hydrothermal reaction, carbon-coating, HCl solution etching, and then selenization treatment. When used as the conversion-typed anode materials (CTAMs) for AMIBs, the yolk-shell FeSe2 @C-3 MCs show advantages. First, the interconnected external carbon shell improves the mechanical strength of electrodes and accelerates ionic migration and electron transmission. Second, the internal electroactive FeSe2 nanoparticles effectively decrease the extent of volume expansion and avoid pulverization when compared with micro-sized solid FeSe2 . Third, the yolk-shell structure provides sufficient inner void to ensure electrolyte infiltration and mobilize the surface and near-surface reactions of electroactive FeSe2 with alkali metal ions. Consequently, the designed yolk-shell FeSe2 @C-3 MCs demonstrate enhanced electrochemical performance in lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries with high specific capacities, long cyclic stability, and outstanding rate capability, presenting potential application as universal anodes for AMIBs.

Blowing Iron Chalcogenides into Two-Dimensional Flaky Hybrids with Superior Cyclability and Rate Capability for Potassium-Ion Batteries.

Chalcogenide-based anodes are receiving increasing attention for rechargeable potassium-ion batteries (PIBs) due to their high theoretical capacities. However, they usually exhibit poor electrochemical performance due to poor structural stability, low conductivity, and severe electrolyte decomposition on the reactive surface. Herein, a method analogous to "blowing bubbles with gum" is used to confine FeS2 and FeSe2 in N-doped carbon for PIB anodes with ultrahigh cyclic stability and enhanced rate capability (over 5000 cycles at 2 A g-1). Several theoretical and experimental methods are employed to understand the electrodes' performance. The density functional theory calculations showed high affinity for potassium adsorption on the FeS2 and FeSe2. The in situ XRD and ex situ TEM analysis confirmed the formation of several intermediate phases of the general formula KxFeS2. These phases have high conductivity and large interlayer distance, which promote reversible potassium insertion and facilitate the charge transfer. Also, the calculated potassium diffusion coefficient during charge/discharge further proves the enhanced kinetics. Furthermore, The FeS2@NC anode in a full cell also exhibits high cyclic stability (88% capacity retention after 120 cycles with 99.9% Coulombic efficiency). Therefore, this work provides not only an approach to overcome several challenges in PIB anodes but also a comprehensive understanding of the mechanism and kinetics of the potassium interaction with chalcogenides.

Suppressing the Shuttle Effect and Dendrite Growth in Lithium-Sulfur Batteries.

Practical applications of lithium-sulfur batteries are simultaneously hindered by two serious problems occurring separately in both electrodes, namely, the shuttle effects of lithium polysulfides and the uncontrollable growth of lithium dendrites. Herein, to explore a facile integrated approach to tackle both problems as well as guarantee the efficient charge transfer, we used two-dimension hexagonal VS2 flakes as the building blocks to assemble nanotowers on the separators, forming a symmetrical double-side-modified polypropylene separator without blocking the membrane pores. Benefiting from the "sulfiphilic" and "lithiophilic" properties, high interfacial electronic conductivity, and the unique hexagonal tower-form nanostructure, the D-HVS@PP separator not only guarantees the effective suppression of the lithium polysulfide shuttle and the rapid ion/electron transfer but also realizes uniform and stable lithium nucleation and growth during cycling. Hence, just at the expense of an 11% increase in the separator weight (0.14 mg cm-2), the D-HVS@PP separator delivers an over 16 times higher initial areal capacity (8.3 mAh cm-2) than a conventional PP separator (0.5 mAh cm-2) under high sulfur-loading conditions (9.24 mg cm-2). Even when used under a low electrolyte/sulfur ratio of 4 mL g-1 and a practically relevant N/P ratio of 1.7, the D-HVS@PP separator still enabled stable cycling with a high cell-level gravimetric energy density. The potentials in broader applications (Li-S pouch battery and Li-LiFePO4 battery) and the promising commercial prospect (large-scale production and recyclability) of the developed separator are also demonstrated.

TiO2@C core@shell nanocomposites: A single precursor synthesis of photocatalyst for efficient solar water treatment.

This study reports the facile synthesis of highly photoactive TiO2@C core@shell nanocomposites through a single alkoxide precursor. TiO2 and carbon-based hybrid nanomaterials are popular photocatalysts owing to their abundance, low toxicity, and high stability, making them strong candidates for practical solar water-treatment applications. However, synthesis of such nanomaterials is often a multi-step process and requires careful control of the external carbon source for producing the desired morphology. In this regard, this study reports the synthesis of well-dispersed TiO2@C nanocomposites without the need of an external carbon source. The resulting photocatalyst was employed for treatment of various water-borne pollutants including several dyes, pharmaceuticals, and pathogens. Rapid mineralization of pollutants could be achieved even with low amounts of catalyst, with the performance well exceeding that of pristine TiO2 and P25 Degussa. Results indicate that incorporation of C increases visible-light absorption and greatly improves the separation of photogenerated charge carriers. Given the facile synthesis and the wide scope of operation, the proposed catalyst could be a significant step towards practical photocatalytic solar water-treatment.

Hollow Multihole Carbon Bowls: A Stress-Release Structure Design for High-Stability and High-Volumetric-Capacity Potassium-Ion Batteries.

Potassium-ion batteries are potential alternatives to lithium-ion batteries for large-scale energy storage considering the low cost and high abundance of potassium. However, it is challenging to obtain stable electrode materials capable of undergoing long-term potassiation/depotassiation due to the high accumulated stress associated with the huge volume variation of the electrode. Here, we simulate the von Mises stress distributions of four different carbon three-dimensional models under an isotropic initial stress by the finite element method and reveal the critical role of the structure of a hollow multihole bowl on the strain-relaxation behavior. In this regard, nitrogen/oxygen codoped carbon hollow multihole bowls (CHMBs) are synthesized via hydrothermal carbonization coupled with an emulsion-templating strategy using biomass as the carbon source. Consistent with our simulation results, the CHMB anode remains stable for over 1000 cycles and delivers a high reversible capacity of 304 mAh g-1 at 0.1 A g-1. In addition to the reduced stress accumulation, the good electrochemical performances are also attributed to the surface capacitive mechanism and the shortened electron/ion transport distance in CHMBs. In particular, the CHMB composite electrode has a volumetric specific capacity 56% higher than that of hollow spheres due to the high tapped density of the bowl-shaped particles.

Enhanced Sulfur Transformation by Multifunctional FeS2/FeS/S Composites for High-Volumetric Capacity Cathodes in Lithium-Sulfur Batteries.

Lithium-sulfur batteries are currently being explored as promising advanced energy storage systems due to the high theoretical specific capacity of sulfur. However, achieving a scalable synthesis for the sulfur electrode material whilst maintaining a high volumetric energy density remains a serious challenge. Here, a continuous ball-milling route is devised for synthesizing multifunctional FeS2/FeS/S composites for use as high tap density electrodes. These composites demonstrate a maximum reversible capacity of 1044.7 mAh g-1 and a peak volumetric capacity of 2131.1 Ah L-1 after 30 cycles. The binding direction is also considered here for the first time between dissolved lithium polysulfides (LiPSs) and host materials (FeS2 and FeS in this work) as determined by density functional theory calculations. It is concluded that if only one lithium atom of the polysulfide bonds with the sulfur atoms of FeS2 or FeS, then any chemical interaction between these species is weak or negligible. In addition, FeS2 is shown to have a strong catalytic effect on the reduction reactions of LiPSs. This work demonstrates the limitations of a strategy based on chemical interactions to improve cycling stability and offers new insights into the development of high tap density and high-performance sulfur-based electrodes.

In vitro evaluation of experimental light activated gels for tooth bleaching.

Dental bleaching is an important part of aesthetic dentistry. Various strategies have been created to enhance the bleaching efficacy. As one such strategy, light-activated nanoparticles that enable localized generation of reactive oxygen species have been developed. Here, we evaluated the cellular response to experimental gels containing these materials in in vitro models. L-929 cells, 3T3 cells, and gingival fibroblasts were exposed to the gels at 50%, 10%, 2%, 0.4%, 0.08%, 0.016%, and 0.0032%. The gels contained TiO2/Ag nanoparticles, TiO2 nanoparticles, hydrogen peroxide (6% hydrogen peroxide), or no added component and were tested with and without exposure to light. Cells were exposed to gels for 24 h or for 30 min. The latter case mimics the clinical situation of a short bleaching gel exposure. Metabolic activity and cell viability were evaluated with MTT and neutral red assays, respectively. We found a dose-dependent reduction of formazan formation and neutral red staining with gels containing TiO2/Ag nanoparticles or TiO2 nanoparticles in the 24 h setting with and without illumination. The strongest reduction, which was not dose-dependent in the evaluated concentrations, was found for the gel containing hydrogen peroxide. Gels with TiO2 nanoparticles showed a similar response to gel without particles. TiO2/Ag gel showed a slightly higher impact. When the gels were removed by rinsing after 30 min of exposure without light illumination, gel containing TiO2/Ag nanoparticles showed a stronger reduction of formazan formation and neutral red staining than gel containing TiO2 particles. Exposure of cells for 30 min under illumination and consequent rinsing off the gels also showed that Ag-containing particles can have a higher impact on the metabolic activity and viability than particles from TiO2. Overall our results show that experimental bleaching gels containing TiO2/Ag or TiO2 nanoparticles are less cytotoxic than hydrogen peroxide-containing gel. When gels are removed, gel containing TiO2/Ag particles exhibit a stronger reduction of metabolic activity and viability than the gel containing TiO2.

Advancing the Use of High-Performance Graphene-Based Multimodal Polymer Nanocomposite at Scale.

The production of an innovative, high-performance graphene-based polymer nanocomposite using cost-effective techniques was pursued in this study. Well-dispersed and uniformly distributed graphene platelets within a polymer matrix, with strong interfacial bonding between the platelets and the matrix, provided an optimal nanocomposite system for industrial interest. This study reports on the reinforcement of high molecular weight multimodal-high-density polyethylene reinforced by a microwave-induced plasma graphene, using melt intercalation. The tailored process included designing a suitable screw configuration, paired with coordinating extruder conditions and blending techniques. This enabled the polymer to sufficiently degrade, predominantly through thermomechanical-degradation, as well as thermo-oxidative degradation, which subsequently created a suitable medium for the graphene sheets to disperse readily and distribute evenly within the polymer matrix. Different microscopy techniques were employed to prove the effectiveness. This was then qualitatively assessed by Raman spectroscopy, X-ray diffraction, rheology, mechanical testing, density measurements, thermal expansion, and thermogravimetric analysis, confirming both the originality as well as the effectiveness of the process.

H2O2 rejuvenation-mediated synthesis of stable mixed-morphology Ag3PO4 photocatalysts.

Ag3PO4 photocatalyst has attracted interest of the scientific community in recent times due to its reported high efficiency for water oxidation and dye degradation. However, Ag3PO4 photo-corrodes if electron accepter such as AgNO3 is not used as scavenger. Synthesis of efficient Ag3PO4 followed by a simple protocol for regeneration of the photocatalyst is therefore a prerequisite for practical application. Herein, we present a facile method for the synthesis of a highly efficient Ag3PO4, whose photocatalytic efficiency was demonstrated using 3 different organic dyes: Methylene Blue (MB), Methyl orange (MO) and Rhodamine B (RhB) organic dyes for degradation tests. Approximately, 19 % of Ag3PO4 is converted to Ag0 after 4.30 hours of continuous UV-Vis irradiation in presence of MB organic dye. We have shown that the Ag/Ag3PO4 composite can be rejuvenated by a simple chemical oxidation step after several cycles of photocatalysis tests. At an optimal pH of 6.5, a mixture of cubic, rhombic dodecahedron, nanosphere and nanocrystals morphologies of the photocatalyst was formed. H2O2 served as the chemical oxidant to re-insert the surface metallic Ag into the Ag3PO4 photocatalyst but also as the agent that can control morphology of the regenerated as-prepared photocatalyst without the need for any other morphology controlling Agent (MCA). Surprisingly, the as- regenerated Ag3PO4 was found to have higher photocatalytic reactivity than the freshly made material and superior at least 17 times in comparison with the conventional Degussa TiO2, and some of TiO2 composites tested in this work.

A Praline-Like Flexible Interlayer with Highly Mounted Polysulfide Anchors for Lithium-Sulfur Batteries.

The development of lithium-sulfur (Li-S) batteries is dogged by the rapid capacity decay arising from polysulfide dissolution and diffusion in organic electrolytes. To solve this critical issue, a praline-like flexible interlayer consisting of high-loading titanium oxide (TiO2 ) nanoparticles and relatively long carbon nanofibers is fabricated. TiO2 nanoparticles with a size gradient occupy both the external and internal of carbon fiber and serve as anchors that allow the chemical adsorption of polysulfides through a conductive nanoarchitecture. The porous conductive carbon backbone helps in the physical absorption of polysulfides and provides redox reaction sites to allow the polysulfides to be reused. More importantly, it offers enough mechanical strength to support a high load TiO2 nanoparticle (79 wt%) that maximizes their chemical role, and can accommodate the large volume changes. Significant enhancement in cycle stability and rate capability is achieved for a readily available sulfur/multi-walled carbon nanotube composite cathode simply by incorporating this hierarchically nanostructured interlayer. The design and synthesis of interlayers by in situ integration of metal oxides and carbon fibers via a simple route offers the potential to advance Li-S batteries for practical applications in the future.