Synergistic Doping for Pseudocapacitance Sites in Alkaline Carbon Supercapacitors

Intertwined carbon networks derived from Polyimide/Cellulose composite as porous electrode for symmetrical supercapacitor

Designing intertwined porous structure is highly desirable to improve the electrochemical performance of carbon materials for supercapacitor. In this contribution, three-dimensional (3D) carbonized polyimide/cellulose (CPC) composite is fabricated via a facile "one-step" carbonization, in which cellulose as cross-linked agent is capable of modulating the molecular structure of polyamic acid, thus ensuring the formation of intertwined porous networks in the obtained carbon skeleton. Benefitting from the high specific surface area (951 m² g^-1) and uniformly distributed pores, the optimized CPC-5 electrode exhibits an outstanding specific capacitance of 300F g^-1 in 6.0 M KOH electrolyte. More impressively, the CPC-5 based symmetrical supercapacitor affords a high energy density of 22.6 Wh kg^-1 at power density of 800 W kg^-1, as well as an exceptional capacitance retention of 91.4% after 10,000 cycles. This work affords an effective strategy to yield a promising polyimide derived carbon material for high-performance supercapacitors.

Fabrication of Superamphiphilic Carbon Using Lignosulfonate for Enhancing Selective Hydrogenation Reactions in Pickering Emulsions

Superamphiphilic materials have great potential to enhance the mass transfer between phases in liquid-liquid catalysis due to their special affinities. Constructing superamphiphilic surfaces that possess superhydrophilic and superhydrophobic properties simultaneously has been a tough assignment. So, exploration of simple methods to prepare such materials using renewable and abundant feedstocks is highly desired. Here, we reported an effective strategy to construct superamphiphilic carbon directly from sodium lignosulfonate, which is a renewable resource from paper industry wastes. From the characterization of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) for superamphiphilic carbon, we found that element C was responsible for the hydrophobic nature and the existence of O and S endowed the carbon with hydrophilic characteristics. Further, micro/nanohierarchical pores were found beneficial for the superamphiphilicity of carbon. Meantime, in the selective hydrogenation of styrene, phenylacetylene, and cis-stilbene in liquid-liquid systems, conversion became double using superamphiphilic carbon compared with blank results, and the yields were three times more than those in blank experiments. The reasons were that superamphiphilic carbon induced the formation of Pickering emulsions and enriched the reactants around catalysts, as concluded by the characterization of confocal laser scanning microscopy and relating contrastive experiments. This work revealed a different route to obtain superamphiphilic carbon and provided a diverse perspective to promote Pickering emulsion catalysis by the superamphiphilicity of carbon.

Atomic Iron Catalysis of Polysulfide Conversion in Lithium-Sulfur Batteries

Lithium-sulfur batteries have been regarded as promising candidates for energy storage because of their high energy density and low cost. It is a main challenge to develop long-term cycling stability battery. Here, a catalytic strategy is presented to accelerate reversible transformation of sulfur and its discharge products in lithium-sulfur batteries. This is achieved with single-atomic iron active sites in porous nitrogen-doped carbon, prepared by polymerizing and carbonizing diphenylamine in the presence of iron phthalocyanine and a hard template. The Fe-PNC/S composite electrode exhibited a high discharge capacity (427 mAh g^-1) at a 0.1 C rate after 300 cycles with the Columbic efficiency of above 95.6%. Besides, the electrode delivers much higher capacity of 557.4 mAh g^-1 at 0.5 C over 300 cycles. Importantly, the Fe-PCN/S has a smaller phase nucleation overpotential of polysulfides than nitrogen-doped carbon alone for the formation of nanoscale of Li₂S as revealed by ex situ SEM, which enhance lithium-ion diffusion in Li₂S, and therefore a high rate performance and remarkable cycle life of Li-sulfur batteries were achieved. Our strategy paves a new way for polysulfide conversion with atomic iron catalysis to exploit high-performance lithium-sulfur batteries.