Carbon intermediate boosted Fe-ZIF derived α-Fe2O3 as a high-performance negative electrode for supercapacitors

Fe2O3/Porous Carbon Composite Derived from Oily Sludge Waste as an Advanced Anode Material for Supercapacitor Application

It is urgent to improve the electrochemical performance of anode for supercapacitors. Herein, we successfully prepare Fe₂O₃/porous carbon composite materials (FPC) through hydrothermal strategies by using oily sludge waste. The hierarchical porous carbon (HPC) substrate and fine loading of Fe₂O₃ nanorods are all important for the electrochemical performance. The HPC substrate could not only promote the surface capacitance effect but also improve the utilization efficiency of Fe₂O₃ to enhance the pseudo-capacitance. The smaller and uniform Fe₂O₃ loading is also beneficial to optimize the pore structure of the electrode and enlarge the interface for faradaic reactions. The as-prepared FPC shows a high specific capacitance of 465 F g^-1 at 0.5 A g^-1, good rate capability of 66.5% retention at 20 A g^-1, and long cycling stability of 88.4% retention at 5 A g^-1 after 4000 cycles. In addition, an asymmetric supercapacitor device (ASC) constructed with FPC as the anode and MnO₂/porous carbon composite (MPC) as the cathode shows an excellent power density of 72.3 W h kg^-1 at the corresponding power density of 500 W kg^-1 with long-term cycling stability. Owing to the outstanding electrochemical characteristics and cycling performance, the associated materials' design concept from oily sludge waste has large potential in energy storage applications and environmental protection.

Sandwich-like MXene/α-Fe2O3-C-MoS2-PEDOT:PSS/MXene Film Electrodes with Ultrahigh Area Capacitance for Flexible Supercapacitors

The restacking of the MXene film limits its development to the high energy density of flexible supercapacitors. In order to promote the application of MXene films in portable electronic devices and miniaturized energy storage devices, it is necessary to increase the area capacitance of MXene films for the pursuit of high energy density. The introduction of α-Fe₂O₃-C-MoS₂-PEDOT:PSS (FMP) into MXene significantly increases the area capacitance. Considering the large number of active sites on the surface of MXene and its excellent hydrophilicity, FMP can be well-compounded with MXene, and the accumulation and loss of FMP can be prevented. Meanwhile, it can reduce the performance degradation caused by the accumulation of MXene's own structure and greatly increase its capacitance value. It is worth mentioning that the MXene/FMP/MXene (M/FMP/M) sandwich structure on the carbon cloth is reasonably designed to show excellent performance. Therefore, the best M/FMP/M electrode could attain a breakthrough in the area capacitance (2700 mF cm^-2 and 541 F g^-1). At the same time, the electrode maintains a fine rate capability and fabulous flexibility. In addition, the symmetrical supercapacitors also show a significant energy density of 371 μW h cm^-2 (12.36 W h·kg^-1), making this sandwich structure electrode a promising candidate for high-energy-density devices.

TEA driven C, N co-doped superfine Fe3O4 nanoparticles for efficient trifunctional electrode materials

Poor conductivity is an obstacle that restricts the development of the electrochemistry performance of Fe₃O₄. In this work, a novel carbon and nitrogen co-doped ultrafine Fe₃O₄ nanoparticles (CN-Fe₃O₄) have been synthesized by triethylamine (TEA) induction and subsequent calcination. The addition of TEA could not only regulate the size of Fe₃O₄ nanoparticles, but also promote the formation of amorphous carbon layer. Well-designed CN-Fe₃O₄ heterostructures provide a highly interconnected porous conductive network, large heterogeneous interface area, large specific surface area and a large number of active sites, which greatly improve conductivity and promote electron transfer and electrolyte diffusion. The prepared CN-Fe₃O₄ electrode exhibits a high specific capacitance of 399.3 mF cm^-2 and good cycling stability. Meanwhile, CN-Fe₃O₄ catalyst exhibits excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities, with overpotentials of 136 and 281 mV at the current density of 10 mA cm^-2, respectively. This work provides a promising approach for the design of high-performance anode materials for supercapacitors and provides profound implications for the development of catalysts with bifunctional catalytic activity.

Metal organic framework derived porous carbon materials excel as an excellent platform for high-performance packaged supercapacitors

Designing and synthesizing new materials with special physical and chemical properties are the key steps to assembling high performance supercapacitors. Metal organic framework (MOF) derived porous carbon materials have drawn great attention in supercapacitors because of their large specific surface area, high chemical/thermal stability and tunable pore structure. Thus, the recent development of porous carbon as an electrode material for supercapacitors is reviewed. The types, design and synthesis strategies of porous carbon are systematically summarized. This review will be divided into three main parts: (1) the design and synthesis of MOF precursors and templates for MOF-derived porous carbon materials; (2) the application of different types of MOF-derived carbon in supercapacitors; and (3) the design of typical structures of porous carbon composites for supercapacitors. Finally, the problems and challenges confronted when using porous carbon are assessed and elaborated, and some suggestions on future research directions are proposed.