Dense networks of graphene nanosheets standing vertically on a current collector can work as numerous electrically conductive bridges to facilitate charge transport and mitigate the constriction/spreading resistance at the interface between the active material and the current collector. The vertically oriented graphene-bridged supercapacitors present excellent rate and power capabilities.

Preparation of graphene from chemical reduction of graphene oxide (GO) is recognized as one of the most promising methods for large-scale and low-cost production of graphene-based materials. This study reports a new, green, and efficient reducing agent (caffeic acid/CA) for GO reduction. The CA-reduced GO (CA-rGO) shows a high C/O ratio (7.15) that is among the best rGOs prepared with green reducing reagents. Electronic gas sensors and supercapacitors have been fabricated with the CA-rGO and show good performance, which demonstrates the potential of CA-rGO for sensing and energy storage applications.G raphene, a two-dimensional (2D) carbon material, has shown great promise in various applications due to its unique structure and properties 1,2 . To promote the practical applications of graphene-based materials, a priority should be given to the exploration for large-scale preparation of high-quality graphene with easy processing route and low cost. Up to now, diverse strategies have been applied for the production of graphene, mainly including mechanical or ultrasonic exfoliation 3 , chemical vapor deposition (CVD)/plasmaenhanced CVD (PECVD) 4,5 , epitaxial growth 6 , electric arc discharge 7 , chemical intercalation 8 , thermal/chemical reduction of graphene oxide (GO) [9][10][11] . Among these methods, chemical reduction of GO is recognized as a versatile and suitable method for the preparation of graphene in bulk quantities at a low cost. Unfortunately, a large number of widely used reducing agents are toxic and/or explosive, such as the commonly-used hydrazine hydrate (HH) 12 and sodium borohydride 13 . As a consequence, continuous endeavors have been directed towards the development and optimization of eco-friendly reducing agents for GO reduction.Recent studies revealed that some natural materials/chemicals are promising substitutes for toxic/explosive reducing agents for GO reduction, such as metals (e.g., iron, zinc, and aluminum) [14][15][16]

The behavior of ion diffusion in nano-confined spaces and its temperature dependence provide important fundamental information about electric double-layer capacitors (EDLCs) employing nano-sized active materials. In this work, the ion diffusion coefficients of NaCl electrolyte confined within neutral and charged graphene nanochannels at different temperatures are investigated using molecular dynamics simulations. The results show that ions confined in neutral nanochannels diffuse faster (along the graphene surfaces) than those in bulk solution, which could be attributed to the relatively smaller concentration in confined spaces and the solvophobic nature of graphene surfaces. In charged nanochannels where the electrostatic interactions between counter-ions and charged channel surfaces govern the motion of ions, the diffusion coefficients are found to be lower than those in the neutral counterparts. The increase of temperature will lead to enhanced vibrant thermal motion of ions. Due to the significant role of ion-surface interactions, ion diffusion coefficients in nano-confined spaces are more stable, that is, insensitive to the temperature variation, than those in bulk solution. The electrical conductivity is further estimated using the Nernst-Einstein equation. The findings of the current work could provide basic data and information for research studies on the thermal effects of graphene-based EDLCs.

The chemical nature of electrolytes has been demonstrated to play a pivotal role in the charge storage of electric double-layer capacitors (EDLCs), whereas primary mechanisms are still partially resolved but controversial. In this work, a systematic exploration into EDL structures and kinetics of representative aqueous electrolytes is performed with numerical simulation and experimental research. Unusually, a novel charging mechanism exclusively predominated by kinetics is recognized, going beyond traditional views of manipulating capacitances preferentially via interfacial structural variations. Specifically, strikingly distinctive EDL structures stimulated by diverse ion sizes, valences, and mixtures manifest a virtually identical EDL capacitance, where the dielectric nature of solvents attenuates ionic effects on electrolyte redistributions, in stark contradiction with solvent-free counterpart and traditional Helmholtz theory. Meanwhile, corresponding kinetics evolve conspicuously with ionic species, intimately correlated with ion-solvent interactions. The achieved mechanisms are subsequently illuminated by electrochemical measurements, highlighting the crucial interplay between ions and solvents in regulating EDLC performances.