Preparation of porous conductive cellulose nanofibril based composite aerogels and performance comparison with films

Polydopamine-Anchored Cellulose Nanofiber Flexible Aerogel with High Charge Transfer as a Substrate for Conductive Materials

In order to obtain a flexible aerogel substrate for conductive materials used in the electrode, polydopamine-anchored cellulose nanofiber (PDA@CNF) was introduced into a polyethylene imine-poly(vinyl alcohol) (PEI-PVA) cross-linking network which used 4-formylphenylboronic acid (4FPBA) as bridge. The incorporation of rigid CNF as a structural scaffold effectively improved the pore architecture of the aerogel, potentially providing substantial advantages for the infiltration and deposition of conductive materials. Additionally, the outstanding stability and flexibility exhibited by the aerogel in aqueous solutions suggest its significant potential for applications in flexible electrodes. Furthermore, electrochemical experiments showed that the rapid pathway formed between PDA and PEI could enhance the charge-transfer rate within the aerogel substrate. It is anticipated that such an enhancement would significantly benefit the electrochemical attributes of the electrode. Inspired by mussels, our introduced PDA-anchored rigid CNF into flexible polymer networks to fabricate aerogel substrates for electrode materials. This study would contribute to the development and utilization of flexible electrodes while reducing carbon footprint in energy production and conversion processes.

Shrinking Devices: Shape-Memory Polymer Fabrication of Micro-and Nanostructured Electrodes

Since their discovery in the 1940s, shape memory polymers (SMPs) have been used in a broad spectrum of applications for research and industry.[1] SMPs can adopt a temporary shape and promptly return to their original form when submitted to an external stimulus. They have proven useful in fields such as wearable and stretchable electronics,[2] biomedicine,[3] and aerospace..[4] These materials are attractive and unique due to their ability to "remember" a shape after being submitted to elastic deformation. By combining the properties of SMPs with the advantages of electrochemistry, opportunities have emerged to develop structured sensing devices through simple and inexpensive fabrication approaches. The use of electrochemistry for signal transduction provides several advantages, including the translation into inexpensive sensing devices that are relatively easy to miniaturize, extremely low concentration requirements for detection, rapid sensing, and multiplexed detection. Thus, electrochemistry has been used in biosensing,[5] pollutant detection,[6] and pharmacological[7] applications, among others. To date, there is no review that summarizes the literature addressing the use of SMPs in the fabrication of structured electrodes for electrochemical sensing. This review aims to fill this gap by compiling the research that has been done on this topic over the last decade.

Sustainable and Scalable Synthesis of 2D Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitor

2D carbon nanomaterials such as graphene, carbon nanosheets, and their derivatives, representing the emerging class of advanced multifunctional materials, have gained great research interest because of their extensive applications ranging from electrochemistry to catalysis. However, sustainable and scalable synthesis of 2D carbon nanosheets (CNs) with hierarchical architecture and irregular structure via a green and low-cost strategy remains a great challenge. Herein, prehydrolysis liquor (PHL), an industrial byproduct of the pulping industry, is first employed to synthesize CNs via a simple hydrothermal carbonization technique. After mild activation with NH4 Cl and FeCl3 , the as-prepared activated CNs (A-CN@NFe) display an ultrathin structure (≈3 nm) and a desirable specific surface area (1021 m2 g-1 ) with hierarchical porous structure, which enables it to be both electroactive materials and structural support materials in nanofibrillated cellulose/A-CN@NFe/polypyrrole (NCP) nanocomposite, and thus endowing nanocomposite with impressive capacitance properties of 2546.3 mF cm-2 at 1 mA cm-2 . Furthermore, the resultant all-solid-state symmetric supercapacitor delivers a satisfactory energy storage ability of 90.1 µWh cm-2 at 250.0 µW cm-2 . Thus, this work not only opens a new window for sustainable and scalable synthesis of CNs, but also offers a double profits strategy for energy storage and biorefinery industry.

Mechanically Strong, Low Thermal Conductivity and Improved Thermal Stability Polyvinyl Alcohol-Graphene-Nanocellulose Aerogel

Porous aerogel materials have advantages of a low density, low thermal conductivity and high porosity, and they have broad application prospects in heat insulation and building energy conservation. However, aerogel materials usually exhibit poor mechanical properties. Single-component aerogels are less likely to possess a good thermal stability and mechanical properties. It is necessary to prepare multiple-composite aerogels by reinforcement to meet practical application needs. In this experiment, a simple preparation method for polyvinyl alcohol (PVA)–graphene (GA)–nanocellulose (CNF) ternary composite aerogels was proposed. This is also the first time to prepare ternary composite aerogels by mixing graphene, nanocellulose and polyvinyl alcohol. A GA–CNF hydrogel was prepared by a one-step hydrothermal method, and soaked in PVA solution for 48 h to obtain a PVA–GA–CNF hydrogel. PVA–GA–CNF aerogels were prepared by freeze drying. The ternary composite aerogel has advantages of excellent mechanical properties, a low thermal conductivity and an improved thermal stability, because strong hydrogen bonds form between the PVA, GA and CNF. The composite aerogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, Brunauer–Emmett–Teller analysis, dynamic thermal analysis, thermogravimetry and thermal constant analysis to characterize the properties of the ternary composite aerogels. The lightweight, low-density and porous PVA–GA–CNF composite aerogels withstood 628 times their mass. The thermal conductivity of the composite aerogels was 0.044 ± 0.005 W/mK at room temperature and 0.045 ± 0.005 W/mK at 70 °C. This solid, low thermal conductivity and good thermal stability PVA–GA–CNF ternary composite aerogel has potential application in thermal insulation.