Synthesis and Characterization of Dense Carbon Films as Model Surfaces to Estimate Electron Transfer Kinetics on Redox Flow Battery Electrodes

N-Doped Carbon Nanonecklaces with Encapsulated BiOCl Nanoparticles as High-Rate Anodes for Lithium-Ion Batteries

The unique two-dimensional layered structure of BiOCl makes it highly promising for energy storage applications. In this study, we successfully synthesized BiOCl nanoparticles encapsulated in N-doped carbon nanonecklaces (BiOCl NPs/N-CNNs) using well-established electrospinning and solvothermal substitution. As an anode material for lithium-ion batteries, BiOCl NPs/N-CNNs exhibited enhanced rate performance, delivering a capacity of 220.2 mA h g-1 at 8 A g-1. Furthermore, it demonstrated remarkable long cycle stability, retaining a capacity of 200.5 mA h g-1 after 9000 cycles with a discharge rate of 8.0 A g-1. The superior electrochemical performance can be attributed to the stacked layered structure of BiOCl, facilitated by van der Waals force, as well as the ingenious nanonecklace structures. These structures not only provide fast ion diffusion pathways but also enhance electrolyte penetration and offer more active sites for Li+ insertion and extraction. Additionally, the nanonecklace structure prevents the aggregation of nanopolyhedra, promoting the complete reaction of BiOCl with Li+. Moreover, the unique nanopolyhedron structure alleviates the stress caused by the volume expansion of Bi nanoparticles during cycling and reduces the internal resistance of the electrode.

Sustainable Biochar Nanosheets Derived from Sweet Sorghum Residues via Superbase Pretreatment

Two-dimensional (2D) sheet-like biochar as promising alternatives to graphene nanosheets has gained significant attention in materials science while being highly restricted by its complicated synthetic steps. In this study, the dimethyl sulfoxide/potassium hydroxide (DMSO/KOH) superbase system was first used to pretreat sweet sorghum residues (SS) and then carbonized to prepare sheet-like biochar. Ascribing to the strong nucleophilicity of DMSO/KOH, a synergistic effect was achieved by partially removing non-cellulosic components in SS and swelling the amorphous region of cellulose, leaving more layered cellulose behind (∼46.5 wt %), which was favorable for the formation of 2D biochar nanosheets with high graphitization degrees (∼93.1%). This strategy was also suitable for other biomass fibers (e.g., straw, wood powders, and nuclear shells) to obtain sheet-like biochar. The resulting sheet-like biochar could be compounded with cellulose nanofibers to achieve the structural design of composites and solve the molding problem of biochar, which was beneficial for dyeing wastewater treatment. Thus, this work provides insight into a simple strategy for developing 2D ultrathin sheet-like biochar from sustainable biomass wastes.