Additive-free carbon nanotube dispersions, pastes, gels, and doughs in cresols.

Cresols are a group of naturally occurring and massively produced methylphenols with broad use in the chemical industry. Here, we report that m-cresol and its liquid mixtures with other isomers are surprisingly good solvents for processing carbon nanotubes. They can disperse carbon nanotubes of various types at unprecedentedly high concentrations of tens of weight percent, without the need for any dispersing agent or additive. Cresols interact with carbon nanotubes by charge transfer through the phenolic hydroxyl proton and can be removed after processing by evaporation or washing, without altering the surface of carbon nanotubes. Cresol solvents render carbon nanotubes polymer-like rheological and viscoelastic properties and processability. As the concentration of nanotubes increases, a continuous transition of four states can be observed, including dilute dispersion, thick paste, free-standing gel, and eventually a kneadable, playdough-like material. As demonstrated with a few proofs of concept, cresols make powders of agglomerated carbon nanotubes immediately usable by a broad array of material-processing techniques to create desirable structures and form factors and make their polymer composites.

Enhanced Energy Density in All-in-One Device Integrating Si Solar Cell and Supercapacitor Using [BMIm]Cl/PVA Gel Electrolyte.

All-in-one systems integrating solar cells and supercapacitors have recently received significant attention because of their high efficiency and portability. Unlike conventional solar photovoltaics, which require external wiring to connect to a battery for energy storage, integrated devices with solar cells and supercapacitors share one electrode, eliminating wiring resistance and facilitating charge transfer. In this work, we designed and fabricated all-in-one devices by combining a silicon solar cell and a supercapacitor with polymer gel electrolytes. Our all-in-one devices incorporating H3PO4/PVA and [BMIm]Cl/PVA exhibited areal capacitances of 452.5 and 550 mF·cm -2 at 0.1 mA·cm-2, respectively, following 100 s of photocharging. Notably, the [BMIm]Cl/PVA-based all-in-one device demonstrated significantly higher maximum energy density and power density compared to both the H3PO4/PVA-based all-in-one device and the values reported in literature. In addition, the cyclic photocharge/galvanostatic discharge process for the [BMIm]Cl/PVA-based all-in-one device represented consistent retention of areal capacitance, affirming its stability across charge-discharge cycles. After 100 s of photocharging, the [BMIm]Cl/PVA-based all-in-one device achieved a total energy efficiency of 1.85%, surpassing the 1.45% efficiency observed in the device using H3PO4/PVA. These results provide valuable insights for the design of self-charging all-in-one devices for portable and wearable applications.

Ligand conjugation of chemically exfoliated MoS2.

MoS2 is a two-dimensional material that is gaining prominence due to its unique electronic and chemical properties. Here, we demonstrate ligand conjugation of chemically exfoliated MoS2 using thiol chemistry. With this method, we modulate the ζ-potential and colloidal stability of MoS2 sheets through ligand designs, thus enabling its usage as a selective artificial protein receptor for ß-galactosidase. The facile thiol functionalization route opens the door for surface modifications of solution processable MoS2 sheets.

Effect of air bubbling on electroless Pd plating for the practical application of hydrogen selective membranes.

In this study, an air bubbling electroless plating (ELP) method was newly developed for the production of Pd composite membranes. The air bubble ELP alleviated the concentration polarization of Pd ions, making it possible to achieve a plating yield of 99.9% in 1 h and form very fine Pd grains with a uniform layer of ∼4.7 µm. A membrane with a diameter of 25.4 mm and a length of 450 mm was produced by the air bubbling ELP, achieving a hydrogen permeation flux of 4.0 × 10-1 mol m-2 s-1 and selectivity of ∼10 000 at 723 K with a pressure difference of 100 kPa. To confirm the reproducibility, six membranes were produced by the same method and assembled in a membrane reactor module to produce high-purity hydrogen by ammonia decomposition. Hydrogen permeation flux and selectivity of the six membranes at 723 K with a pressure difference of 100 kPa were 3.6 × 10-1 mol m-2 s-1 and ∼8900, respectively. An ammonia decomposition test with an ammonia feed rate of 12 000 mL min-1 showed that the membrane reactor produced hydrogen with >99.999% purity and a production rate of 1.01 Nm3 h-1 at 748 K with a retentate stream gauge pressure of 150 kPa and a permeation stream vacuum of -10 kPa. The ammonia decomposition tests confirmed that the newly developed air bubbling ELP method affords several advantages, such as rapid production, high ELP efficiency, reproducibility, and practical applicability.

Hierarchically Porous Carbon Networks Derived from Chitosan for High-Performance Electrochemical Double-Layer Capacitors.

Activated carbon (AC) compounds derived from biomass precursors have garnered significant attention as electrode materials in electric double-layer capacitors (EDLCs) due to their ready availability, cost-effectiveness, and potential for mass production. However, the accessibility of their active sites in electrochemistry has not been investigated in detail. In this study, we synthesized two novel macro/micro-porous carbon structures prepared from a chitosan precursor using an acid/potassium hydroxide activation process and then examined the relationship between their textural characteristics and capacitance as EDLCs. The material characterizations showed that the ACs, prepared through different activation processes, differed in porosity, with distinctive variations in particle shape. The sample activated at 800 °C (Act-chitosan) was characterized by plate-shaped particles, a specific surface area of 4128 m2/g, and a pore volume of 1.87 cm3/g. Assessment of the electrochemical characteristics of Act-chitosan showed its remarkable capacitance of 183.5 F/g at a scan rate of 5 mV/s, and it maintained exceptional cyclic stability even after 10,000 cycles. The improved electrochemical performance of both chitosan-derived carbon structures could thus be attributed to their large, well-developed active sites within pores < 2 nm, despite the fact that interconnected macro-porous particles can enhance ion accessibility on electrodes. Our findings provide a basis for the fabrication of biomass-based materials with promising applications in electrochemical energy storage systems.

Improving Uniformity and Reproducibility of Hybrid Perovskite Solar Cells via a Low-Temperature Vacuum Deposition Process for NiOx Hole Transport Layers.

Recently, the trend in inverted hybrid perovskite solar cells (PVSCs) has been to utilize NiOx as hole transport layers. However, the majority of reported solution-processed NiOx films require a high-temperature thermal annealing process, which is unfavorable for large-scale manufacturing and suffers from lack of uniformity. We report, for the first time, e-beam evaporation as a low-temperature vacuum process for the deposition of NiOx hole transport layers for PVSCs. Device characterization shows that efficiency is on par with solution-processed methods, the highest efficiency at 15.4% with no obvious hysteresis. Differences are found to be due to the presence of more Ni3+ in e-beam evaporated NiOx, which are responsible for a lower transmittance but higher conductivity. Most importantly, e-beam-evaporated NiOx-based PVSCs show greater uniformity and reproducibility compared to spin-coated NiOx-based PVSCs. Finally, e-beam-evaporated NiOx has the additional advantage of being produced by a low-temperature deposition process and applicable over large areas. This work, therefore, represents a significant step toward large-area PVSCs, where e-beam evaporation can be used for the low-temperature uniform deposition of charge-transport layers, such as NiOx.

Enhanced Electrocatalytic Properties of Transition-Metal Dichalcogenides Sheets by Spontaneous Gold Nanoparticle Decoration.

Here, we report that transition-metal dichalcogenides such as MoS2 and WS2 can be decorated with gold nanoparticles by a spontaneous redox reaction with hexachloroauric acid in water. The resulting gold nanoparticles tend to grow at defective sites, and therefore, selective decorations at the edges and the line defects in the basal planes of bulk single crystals were observed. The lithium intercalation-exfoliation process makes the basal planes of chemically exfoliated MoS2 and WS2 sheets much more defective than their single-crystalline counterparts, leading to a more uniform and higher-density deposition of gold nanoparticles. Due to the greatly improved charge transport between adjacent sheets, the resulting MoS2/Au and WS2/Au hybrids show significantly enhanced electrocatalytic performance toward hydrogen evolution reactions.