Cellulose-based Conductive Materials for Bioelectronics

The growing demand for electronic devices has led to excessive stress on Earth's resources, necessitating effective waste management and the search for renewable materials with minimal environmental impact. Bioelectronics, designed to interface with the human body, have traditionally been made from inorganic materials, such as metals, which, while having suitable electrical conductivity, differ significantly in chemical and mechanical properties from biological tissues. This can cause issues such as unreliable signal collection and inflammatory responses. Recently, natural biopolymers such as cellulose, chitosan, and silk have been explored for flexible devices, given their chemical uniqueness, shape flexibility, ease of processing, mechanical strength, and biodegradability. Cellulose is the most abundant natural biopolymer, has been widely used across industries, and can be transformed into electronically conductive carbon materials. This review focuses on the advancements in cellulose-based conductive materials for bioelectronics, detailing their chemical properties, methods to enhance conductivity, and forms used in bioelectronic applications. It highlights the compatibility of cellulose with biological tissues, emphasizing its potential in developing wearable sensors, supercapacitors, and other healthcare-related devices. The review also addresses current challenges in this field and suggests future research directions to overcome these obstacles and fully realize the potential of cellulose-based bioelectronics.

Solvothermally Synthesized Nickel-Doped Marigold-Like SnS2 Microflowers for High-Performance Supercapacitor Electrode Materials

Two-dimensional transition-metal dichalcogenides (TMDs) have emerged as promising capacitive materials for supercapacitors owing to their layered structure, high specific capacity, and large surface area. Herein, Ni-doped SnS2 microflowers were successfully synthesized via a facile one-step solvothermal approach. The obtained Ni-doped SnS2 microflowers exhibited a high specific capacitances of 459.5 and 77.22 F g-1 at current densities of 2 and 10 A g-1, respectively, in NaClO4 electrolyte, which was found to be higher than that of SnS2-based electrodes in various electrolytes such as KOH, KCl, Na2SO4, NaOH, and NaNO3. Additionally, these microflowers demonstrate a good specific energy density of up to 51.69 Wh kg-1, at a power density of 3204 Wkg-1. Moreover, Ni-doped SnS2 microflowers exhibit a capacity retention of 78.4% even after 5000 cycles. Better electrochemical performance of the prepared electrode may be attributed to some important factors, including the utilization of a highly ionic conductive and less viscous NaClO4 electrolyte, incorporation of Ni as a dopant, and the marigold flower-like morphology of the Ni-doped SnS2. Thus, Ni-doped SnS2 is a promising electrode material in unconventional high-energy storage technologies.

Enhancing Electron/Ion Transport in SnO2 Quantum Dots Decorated Polyaniline/Graphene Hybrid Fibers for Wearable Supercapacitors with High Energy Density

Fiber-based supercapacitors are the potential power sources in the field of wearable electronics and energy storage textiles due to their unique advantages of electrochemical properties and mechanical flexibility, but achieving high energy density and practical energy supply still presents some challenges. In this study, we reported an approach of microfluidic assisted wet-spinning to fabricate SnO2 quantum dots encapsulated polyaniline/graphene hybrid fibers (SnO2 QDs@PGF) by incorporating uniformly polyaniline into graphene fibers and covalently bridging SnO2 quantum dots. The assembled SnO2 QDs@PGF fiber-typed flexible supercapacitors exhibit an ultralarge specific areal capacitance of 925 mF cm-2 in PVA/H2SO4, superior rate capabilities, and capacitance retention of 88% after 8000 cycles, indicating that the SnO2 QDs@PGF possess near-ideal capacitance properties, efficient ion transfer rate, and good cycling stability. In the EMITFSI/PVDF-HFP electrolyte system, SnO2 QDs@PGF realize a wide operating potential window of 2.5 V, a specific areal capacitance of 678.4 mF cm-2, and an energy density of 147.2 μWh cm-2 at 500 μW cm-2, which can be utilized to power an alarm clock, an electronic timer, and a desk lamp with a requirement of a 3 V battery. The exceptional performance of the SnO2 QDs@PGF can be attributed to the molecular-level homogeneous composite of granular polyaniline and graphene nanosheets and the interfacial C-O-Sn covalent coupling strategy employed between SnO2 QDs and PGF. These avenues not only effectively prevent the undesirable restacking of graphene nanosheets but also increase the interlayer electroactive sites, ordered ion diffusion channels, and strong interfacial charge transfer.

Investigation of the supercapacitor behavior of MoS2 and Fe-doped MoS2 nano-flowers synthesized using the hydrothermal method

Flower-like nanosheets of Fe-doped MoS2 with high porosity exhibit better electrochemical activities in supercapacitors.

Cellulose-Derived Nanostructures as Sustainable Biomass for Supercapacitors: A Review

Sustainable biomass has attracted a great attention in developing green renewable energy storage devices (e.g., supercapacitors) with low-cost, flexible and lightweight characteristics. Therefore, cellulose has been considered as a suitable candidate to meet the requirements of sustainable energy storage devices due to their most abundant nature, renewability, hydrophilicity, and biodegradability. Particularly, cellulose-derived nanostructures (CNS) are more promising due to their low-density, high surface area, high aspect ratio, and excellent mechanical properties. Recently, various research activities based on CNS and/or various conductive materials have been performed for supercapacitors. In addition, CNS-derived carbon nanofibers prepared by carbonization have also drawn considerable scientific interest because of their high conductivity and rational electrochemical properties. Therefore, CNS or carbonized-CNS based functional materials provide ample opportunities in structure and design engineering approaches for sustainable energy storage devices. In this review, we first provide the introduction and then discuss the fundamentals and technologies of supercapacitors and utilized materials (including cellulose). Next, the efficacy of CNS or carbonized-CNS based materials is discussed. Further, various types of CNS are described and compared. Then, the efficacy of these CNS or carbonized-CNS based materials in developing sustainable energy storage devices is highlighted. Finally, the conclusion and future perspectives are briefly conferred.