Demonstration of a Gel-Polymer Electrolyte-Based Electrochromic Device Outperforming Its Solution-Type Counterpart in All Merits: Architectural Benefits of CeO2 Quantum Dot and Nanorods.

For years, solution-type electrochromic devices (ECDs) have intrigued researchers' interest and eventually rendered themselves into commercialization. Regrettably, challenges such as electrolyte leakage, high flammability, and complicated edge-encapsulation processes limit their practical utilization, hence necessitating an efficient alternate. In this quest, although the concept of solid/gel-polymer electrolyte (SPE/GPE)-based ECDs settled some issues of solution-type ECDs, an array of problems like high operating voltage, sluggish response time, and poor cycling stability have paralyzed their commercial applicability. Herein, we demonstrate a choreographed-CeO2-nanofiller-doped GPE-based ECD outperforming its solution-type counterpart in all merits. The filler-incorporated polymer electrolyte assembly was meticulously weaved through the electrospinning method, and the resultant host was employed for immobilizing electrochromic viologen species. The filler engineering benefits conceived through the tuned shape of CeO2 nanorod and quantum dots, along with the excellent redox shuttling effect of Ce3+/Ce4+, synchronously yielded an outstanding class of GPE, which upon utilization in ECDs delivered impressive electrochromic properties. A combination of features possessed by a particular device (QD-NR/PVDF-HFP/IL/BzV-Fc ECD) such as exceptionally low driving voltage (0.9 V), high transmittance change (ΔT, ∼69%), fast response time (∼1.8 s), high coloration efficiency (∼339 cm2/C), and remarkable cycling stability (∼90% ΔT-retention after 25,000 cycles) showcased a striking potential in the yet-to-realize market of GPE-based ECDs. This study unveils the untapped potential of choreographed nanofillers that can promisingly drive GPE-based ECDs to the doorstep of commercialization.

Morphological Features of SiO2 Nanofillers Address Poor Stability Issue in Gel Polymer Electrolyte-Based Electrochromic Devices.

Nanofillers' applicability in gel polymer electrolyte (GPE)-based devices skyrocketed in the last decade as soon as their remarkable benefits were realized. However, their applicability in GPE-based electrochromic devices (ECDs) has hardly seen any development due to challenges such as optical inhomogeneity brought by incompetent nanofiller sizes, transmittance drop due to higher filler loading (usually required), and poor methodologies of electrolyte fabrication. To address such issues, herein, we demonstrate a reinforced polymer electrolyte tailored through poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP),1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), and four types of mesoporous SiO2 nanofillers, porous (distinct morphologies) and nonporous, two each. The synthesized electrochromic species 1,1'-bis(4-fluorobenzyl)-4,4'-bipyridine-1,1'-diium tetrafluoroborate (BzV, 0.05 M), counter redox species ferrocene (Fc, 0.05 M), and supporting electrolyte (TBABF4, 0.5 M) were first dissolved in propylene carbonate (PC) and then immobilized in an electrospun PVDF-HFP/BMIMBF4/SiO2 host. We distinctly observed that spherical (SPHS) and hexagonal pore (MCMS) morphologies of fillers endowed higher transmittance change (ΔT) and coloration efficiency (CE) in utilized ECDs; particularly for the MCMS-incorporated ECD (GPE-MCMS/BzV-Fc ECD), ΔT reached ∼62.5% and CE soared to 276.3 cm2/C at 603 nm. The remarkable benefit of filler's hexagonal morphology was also seen in the GPE-MCMS/BzV-Fc ECD, which not only marked an astounding ionic conductivity (σ) of ∼13.5 × 10-3 S cm-1 at 25 °C, thus imitating the solution-type ECD's behavior, but also retained ∼77% of initial ΔT after 5000 switching cycles. The enhancement in ECD's performance resulted from merits brought by filler geometries such as the proliferation of Lewis acid-base interaction sites due to the high surface-to-volume ratio, the creation of percolating tunnels, and the emergence of capillary forces triggering facile ion transportation in the electrolyte matrix.

Comparative Study of Li-CO2 and Na-CO2 Batteries with Ru@CNT as a Cathode Catalyst.

Alkali metal-carbon dioxide (Li/Na-CO2) batteries have generated widespread interest in the past few years owing to the attractive strategy of utilizing CO2 while still delivering high specific energy densities. Among these systems, Na-CO2 batteries are more cost effective than Li-CO2 batteries because the former uses cheaper and abundant Na. Herein, a Ru/carbon nanotube (CNT) as a cathode material was used to compare the mechanisms, stabilities, overpotentials, and energy densities of Li-CO2 and Na-CO2 batteries. The potential of Na-CO2 batteries as a viable energy storage technology was demonstrated.

Curtailing the Overpotential of Li-CO2 Batteries with Shape-Controlled Cu2 O as Cathode: Effect of Illuminating the Cathode.

Li-air batteries are limited to lab-scale research owing to the uninterrupted formation of discharge products. In the case of Li-CO2 batteries, the increase in overpotential caused by Li2 CO3 formation results in cell death. In this study, Cu2 O crystals having three different types of shapes (i.e., cubic, octahedral, and rhombic) were synthesized to compare their catalytic activity toward CO2 reactions. The full-cycle and long-term stability test revealed that rhombohedral Cu2 O facilitates Li2 CO3 decomposition more efficiently than that of cubic and octahedral Cu2 O. The cycle was extended to investigate the photocatalytic activity of the rhombic Cu2 O by illuminating the cell. The repeated cycles to 1 h showed a maximum overpotential of 1.5 V, which is 0.5 V lower than that of the cell without illumination. A postmortem analysis of the cell after dividing the cycles into segments demonstrated interesting results concerning the role of light and Cu2 O during the cell cycle.

Spinel Zinc Cobalt Oxide (ZnCo2O4) Porous Nanorods as a Cathode Material for Highly Durable Li-CO2 Batteries.

Li-CO2 batteries are of great interest among researchers due to their high energy density and utilization of the greenhouse gas CO2 to produce energy. However, several shortcomings have been encountered in the practical applications of Li-CO2 batteries, among which their poor cyclability and high charge overpotential necessary to decompose the highly insulating discharge product (Li2CO3) are the most important. Herein, the spinel zinc cobalt oxide porous nanorods with carbon nanotubes (ZnCo2O4@CNTs) composite is employed as a cathode material in Li-CO2 batteries to improve the latter's cycling performance. The ZnCo2O4@CNT cathode-based Li-CO2 battery exhibited a full discharge capacity of 4275 mAh g-1 and excellent cycling performance over 200 cycles with a charge overpotential below 4.3 V when operated at a current density of 100 mA g-1 and fixed capacity of 500 mAh g-1. The superior performance of the ZnCo2O4@CNT cathode composite was attributed to the synergistic effects of ZnCo2O4 and CNT. The highly porous ZnCo2O4 nanorod structures in the ZnCo2O4@CNT catalyst showed enhanced catalytic activity/stability, which effectively promoted CO2 diffusion during the discharging process and accelerated Li2CO3 decomposition at a low charge overpotential.

Aqueous-Phase Synthesis of Size-Tunable Copper Nanocubes for Efficient Aryl Alkyne Hydroboration.

Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC) surfactant, copper acetate, and sodium ascorbate reductant heated at 100 °C for 40 min. Copper nanowires with an average length of 25 µm can also be prepared this way by simply increasing the volume of sodium ascorbate introduced. Small shifts in the plasmonic absorption band positions with tunable particle sizes have been observed. The copper nanocubes were employed to catalyze hydroboration of phenylacetylene and various substituted aryl alkynes with 100 % (E)-product selectivity and 82-95 % product yields. The copper nanocubes are cheap to make and should catalyze a broad scope of organic coupling reactions.

Tracing the Surfactant-Mediated Nucleation, Growth, and Superpacking of Gold Supercrystals Using Time and Spatially Resolved X-ray Scattering.

The nucleation and growth process of gold supercrystals in a surfactant diffusion approach is followed by simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS), supplemented with scanning electron microscopy. The results indicate that supercrystal nucleation can be activated efficiently upon placing a concentrated surfactant solution of a nematic phase on top of a gold nanocrystal solution droplet trapped in the middle of a vertically oriented capillary tube. Supercrystal nuclei comprised of tens of gold nanocubes are observed nearly instantaneously in the broadened liquid-liquid interface zone of a steep gradient of surfactant concentration, revealing a diffusion-kinetics-controlled nucleation process. Once formed, the nuclei can sediment into the naoncrystal zone below, and grow efficiently into cubic or tetragonal supercrystals of ∼1 µm size within ∼100 min. Supercrystals matured during sedimentation in the capillary can accumulate and face-to-face align at the bottom liquid-air interface of the nanocrystal droplet. This is followed by superpacking of the supercrystals into highly oriented hierarchical sheets, with a huge number of gold nanocubes aligned for largely coherent crystallographic orientations.