Hao Zhuo

3D hierarchical porous N-doped carbon aerogel from renewable cellulose: an attractive carbon for high-performance supercapacitor electrodes and CO2 adsorption

Hierarchical porous N-doped carbons have attracted great interest in energy storage and CO2 capture applications due to their unique porous structure and physicochemical properties. Fabrication of cost-effective and eco-friendly hierarchical porous N-doped carbons from renewable biomass resources is a sustainable route for future energy storage. However, it is still a big challenge to produce N-doped carbons with hierarchical porous structure from cellulose, which is the most abundant and widely available renewable resource on earth. Here, we designed a facile and effective strategy to produce hierarchical porous N-doped carbons from cellulose for high-performance supercapacitor and CO2 capture applications. In this method, hierarchical porous cellulose aerogels were first obtained via a dissolving–gelling process and then carbonized in NH3 atmosphere to give hierarchical porous N-doped carbon aerogels with more interconnected macropores and micropores. Due to the unique porous structure and physicochemical properties, the as-prepared N-doped carbon aerogels had a high specific capacitance of 225 F g−1 (0.5 A g−1) and an outstanding cycling stability. For the first time, we also demonstrated that this N-doped carbon aerogel exhibited a exceptional CO2 adsorption capacity of 4.99 mmol g−1, which is much higher than those of other porous carbons. This novel hierarchical porous N-doped carbon has great potential applications in CO2 capture, energy storage, porous supports, and electrochemical catalysis.

Flexible nanocomposites with ultrahigh specific areal capacitance and tunable properties based on a cellulose derived nanofiber-carbon sheet framework coated with polyaniline

Flexible supercapacitors are extremely important for future various electronic devices. However, the development of cost-efficient and high-performance flexible supercapacitor electrodes remains a big challenge today. Herein, we present a novel flexible nanocomposite based on a cellulose-derived framework coated with polyaniline (PANI). In this nanocomposite, the cellulose nanofiber (CNF) provides mechanical strength due to its interconnected network, while the strapped cellulose-derived carbon sheet (CCS) with a unique morphology produces a porous structure and offers fast transfer pathways for the efficient diffusion of electrode ions. PANI imparts conductivity to the CNF and provides abundant active sites for charge storage. The porous structure and supercapacitive performance of this kind of nanocomposite can be easily tailored by changing the feeding mass ratio of the CNF, CCS, and PANI. A relatively low CCS loading can produce a flexible electrode with an ultrahigh specific areal capacitance of 1838.5 mF cm−2 (150 F g−1) (1 mA cm−2), while high CCS loading can produce a free-standing electrode with a higher specific areal capacitance of 3297.2 mF cm−2 (220 F g−1) (1 mA cm−2). Besides, the robust three-dimensional network guarantees good cycling stability of the nanocomposite electrode (more than 83% retention after 3000 cycles). The tunable structure and electrochemical performance make the nanocomposite an ideal electrode for various electronic devices.

A new strategy to tailor the structure of sustainable 3D hierarchical porous N-self-doped carbons from renewable biomass for high-performance supercapacitors and CO2 capture

Hierarchical porous N-doped carbons show great potential applications in energy storage and CO2 capture. Renewable biomass chitosan, which is abundant and simultaneously contains large amounts of N and C, is an ideal alternative to fossil resources for sustainable and scale-up production of cost-effective N-self-doped carbons. In this work, we employed a new and effective strategy to obtain 3D hierarchical porous N-self-doped carbons from chitosan. The hierarchical porous structure of the N-self-doped carbons could be easily tailored to obtain nanorod interconnected and fiber-wall interconnected architectures without using any porogen, catalyst or activator. The nanorod interconnected porous carbon displayed a high specific surface area of 1408 m2 g−1 while the fiber-wall interconnected porous carbon exhibited an excellent specific capacitance of 261 F g−1 (0.5 A g−1) due to the desirable hierarchical framework. In addition, these hierarchical porous carbons had a good CO2 capture performance (3.07–3.44 mmol g−1 at 25 °C). This unique method is supposed to be a new strategy to create novel 3D hierarchical porous carbons for promising applications in supercapacitors, lithium ion batteries, fuel cells and sorbents.

A Supercompressible, Elastic, and Bendable Carbon Aerogel with Ultrasensitive Detection Limits for Compression Strain, Pressure, and Bending Angle

Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices.

A foldable composite electrode with excellent electrochemical performance using microfibrillated cellulose fibers as a framework

There is an increasing demand for developing environment-friendly and cost-effective strategies to synthesize high-performance flexible supercapacitor electrode materials. Biomass-derived carbon materials are very promising and attractive candidates due to their outstanding advantages. Herein, we prepared a foldable composite electrode based on a chitosan-derived N-self-doped carbon sheet (N-CS) and a microfibrillated cellulose fiber (MCF) framework. The N-CS plays a key role in tailoring the electrochemical behavior of electrode, while the MCF framework offers a porous structure with excellent mechanical foldability. In situ PANI improves the conductivity of the MCF framework and provides abundant active redox sites for energy storage. This foldable composite electrode possesses a high specific areal capacitance of 1688.8 mF cm−2 (139.6 F g−1, 84.4 F cm−3) at 1 mA cm−2 and an energy density of 11.75 mW h cm−3 at a power density of 25 mW cm−3. Furthermore, benefitting from the mechanical foldability of the MCF framework, the composite can perform well in the folded state. Besides, as a PANI-containing electrode material, its long-term cycling stability is pretty good (more than 84% retention after 5000 cycles). Therefore, this work provides an environment-friendly, cost-effective and high-performance electrode material for foldable electronic devices.