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[Display omitted] • Pore size shows significant effect on the capacitive performance of biomass-derived porous carbon materials. • Pore characteristics are influenced by the probe molecules and the corresponding calculation models. • The microstructure of biomass derived porous carbon is influenced by the structure and components of precursor and synthesis method. • Challenges are existing and new strategies are required to boost the capacitance performance of biomass derived porous carbon. As the world's demand for green energy storage systems continues to increase, electrochemical double-layer supercapacitors based on porous carbon electrodes are receiving more attention than ever. Porous carbon materials can be designed and synthesized from biomass residues/extracts through various technologies, which realizes the value-added utilization of biomass and meets the targets of circular economy. Pore characteristics are particularly important for the capacitive performance of carbon-based electrodes. This review outlines the biomass-derived porous carbon materials and their corresponding capacitive properties, which are divided into biomass-derived ultra/super-microporous carbon, mesoporous carbon, macroporous carbon and hierarchical porous carbon according to the category of pore size. The synthesis methods, pore characteristic testing probes/calculation models and capacitance performance are discussed in detail, and the corresponding advantages and bottlenecks are pointed out critically. Emphasis is laid on the research status and development trend of biomass-derived hierarchical porous carbon materials, including the effects of the structure and composition of biomass precursors, advanced nanotechnologies and the proportion of various pores in carbonaceous products on the capacitance performance. Finally, the coping strategies are proposed for the further development of high capacitance biomass-derived porous carbon materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The recent progress of electrospun nanofibers as electrocatalysts for flexible metal-air batteries has been reviewed. • The fundamental principles of electrospinning technique have been introduced. • The importance of bifunctional electrocatalysts for oxygen reduction and oxygen evolution in metal-air batteries has been highlighted. • Future perspectives of novel electrospun nanofibers composite for flexible metal-air batteries have been proposed. Rechargeable metal-air (O 2) batteries have been regarded as the promising candidates for wearable and flexible energy devices owing to their outstanding energy density, low cost, and high safety. Generally, the electrocatalyst at air cathode plays a significant role in various metal-air (O 2) batteries. As a versatile and efficient technique, electrospinning has been considered as a powerful method to fabricate nanofibers, which hold great potential as bifunctional electrocatalysts for such batteries. Although great progresses have been achieved in improving the electrochemical performance of catalysts in recent years, some critical challenges still maintain. In this review, the advanced electrospun carbon nanofiber-based electrocatalysts for flexible metal-air batteries have been summarized. Then, additional discussions have been included focusing on the advantages and characteristics of different nanofibers and some special requirements for various flexible metal-air batteries. Moreover, some current challenges and future prospects in the development of electrospun carbon nanomaterials for flexible metal-air cathode catalysts have been rationally analyzed. [ABSTRACT FROM AUTHOR]

Superhydrophobic surface has potential applications in various fields due to its excellent water repellency. In particular, fluorine-free superhydrophobic film has attracted extensive attentions. In this study, an eco-friendly and rewritable superhydrophobic coating is successfully prepared by a simple spray-coating method. Hydrophilic silica nanoparticles are immobilized on a substrate by water-soluble polyvinyl alcohol (PVA), and then the surface is further modified by polydimethylsiloxane (PDMS) to obtain a superhydrophobic coating. The prepared coating has a water contact angle of 160o, and exhibits good stability. Most importantly, when the superhydrophobic coating is no longer needed, it can be removed and the substrate can be reused. The eco-friendly and rewritable superhydrophobic coating should have promising potentials in daily life. Unlabelled Image • Eco-friendly superhydrophobic coatings are prepared using water-soluble polyvinyl alcohol by a spray-coating method. • The superhydrophobic coatings show good self-cleaning ability and low water adhesion. • The superhydrophobic coatings are erasable and rewritable. [ABSTRACT FROM AUTHOR]