Three-dimensional carbon fiber electrodes prepared by electrospinning and solution blowing are shown to be excellent electrode materials for bioelectrochemical systems such as microbial fuel cells or microbial electrolysis cells. The bioelectrocatalytic anode current density is shown to reach values of up to 30 A m⁻², which represents the highest reported values for electroactive microbial biofilms.

Commonly, commercially available carbon foam derived from polymers shows brittle characteristics. In this paper, the concept of preparing an elastic carbon foam via the direct carbonization of a polymer foam is presented. A novel carbon foam with a 3D elastic interconnected network was prepared by the direct carbonization of melamine foam. The as-prepared carbon foam exhibited characteristics including excellent elasticity, extremely high porosity of over 99.6%, being lightweight with a density of 5 mg cm⁻³, a high specific surface area, tailored electrical conductivity, super-hydrophobicity and excellent absorptive properties towards oil and organic solvents. Two example applications as flexible electrodes and as an organic chemical absorbent have been demonstrated. For use as an electrode in supercapacitors, it could exhibit a specific capacitance of more than 250 F g⁻¹ in 1 M H₂SO₄ at a charge/discharge current density of 0.5 A g⁻¹. For use as an absorbent, it was able to absorb 148 to 411 times its own weight of organic solvents depending on the density of the solvents.

Nylon-4,6 nanofibres with diameters ranging from about 1 µm down to 1 nm were prepared by electrospinning. The fibre diameter was varied by adjusting the concentration of the polymer solution. Electrospinning of a concentrated solution of as high as 20% nylon-4,6 by weight in formic acid produced a ribbon-like electrospun fibre with a ribbon width of about 850 nm. A semi-dilute concentration of 2% nylon-4,6 by weight produced the thinnest nylon-4,6 nanofibres with diameters of 1.6 nm or less. A small amount of pyridine was added to the electrospinning solution to avoid the formation of beaded nanofibres in the course of electrospinning at low concentrations. Scanning and transmission electron microscopy were used to characterize the size of the nanofibres. An ultra-thin nylon-4,6 nanofibre of 1.2 nm diameter might contain six or seven nylon-4,6 molecules in a typical cross-section of the fibre.

Growing concern regarding the impact of fossil fuels has led to demands for the development of green and renewable materials for advanced electrochemical energy storage devices. Biopolymers with unique hierarchical structures and physicochemical properties, serving as an appealing platform for the advancement of sustainable energy, have found widespread application in the gel electrolytes of supercapacitors. In this Review, we outline the structure and characteristics of various biopolymers, discuss the proposed mechanisms and assess the evaluation metrics of gel electrolytes in supercapacitor devices, and further analyze the roles of biopolymer materials in this context. The state-of-the-art electrochemical performance of biopolymer-based hydrogel electrolytes for supercapacitors and their multiple functionalities are summarized, while underscoring the current technical challenges and potential solutions. This Review is intended to offer a thorough overview of recent developments in biopolymer-based hydrogel electrolytes, highlighting research concerning green and sustainable energy storage devices and potential avenues for further development.