Metal–Organic Framework Derived Spindle-like Carbon Incorporated α-Fe₂O₃ Grown on Carbon Nanotube Fiber as Anodes for High-Performance Wearable Asymmetric Supercapacitors

Abstract

Iron oxide (FeO) has drawn much attention because of its high theoretical capacitance, wide operating potential window, low cost, natural abundance, and environmental friendliness. However, the inferior conductivity and insufficient ionic diffusion rate of a simple FeO electrode leading to the low specific capacitance and poor rate performance of supercapacitors have impeded its applications. In this work, we report a facile and cost-effective method to directly grow MIL-88-Fe metal-organic framework (MOF) derived spindle-like α-FeO@C on oxidized carbon nanotube fiber (S-α-FeO@C/OCNTF). The S-α-FeO@C/OCNTF electrode is demonstrated with a high areal capacitance of 1232.4 mF/cm at a current density of 2 mA/cm and considerable rate capability with capacitance retention of 63% at a current density of 20 mA/cm and is well matched with the cathode of the Na-doped MnO nanosheets on CNTF (Na-MnO NSs/CNTF). The electrochemical test results show that the S-α-FeO@C/OCNTF//Na-MnO NSs/CNTF asymmetric supercapacitors possess a high specific capacitance of 201.3 mF/cm and an exceptional energy density of 135.3 μWh/cm. Thus, MIL-88-Fe MOF derived S-α-FeO@C will be a promising anode for applications in next-generation wearable asymmetric supercapacitors.

Carbon Transition‐metal Oxide Electrodes: Understanding the Role of Surface Engineering for High Energy Density Supercapacitors

“…[134,135] For instance, Zhou et al suggested that in order to optimize the performance of Fe 2 O 3 -based fibrous electrode, it is vital to control the surface area of Fe 2 O 3 nanostructure on a conductive fiber substrate to amplify the redox kinetics. [136] The group utilized MIL-88-Fe, a representative Fe-based MOF material, to fabricate a spindle-like α-Fe 2 O 3 @C on oxidized carbon nanotube fiber (S-α-Fe 2 O 3 @C/OCNTF). Specifically, the hybrid electrode was prepared by oxidizing pristine CNTFs with an electrochemical cyclic voltammetric (CV) method to achieve OCNTFs, followed by facile hydrothermal treatment and calcination to fully coat the fiber substrate with MIL-88 Fe derived α-Fe 2 O 3 @C. Supported by high surface area and robust nanostructure, the S-α-Fe 2 O 3 @C/OCNTF electrode displayed a superior specific capacitance of 1232.4 mF cm À 2 at a current density of 2 mA cm À 2 .…”

Partially Graphitized Iron−Carbon Hybrid Composite as an Electrochemical Supercapacitor Material

“…In the field of mesoporous materials, carbon‐based functional materials represent the most investigated electrode materials for energy storage applications due to their excellent electrochemical activity as well as other advantages, including low costs and environmental friendliness . A gazillions of strategies have been attempted by choosing different precursors to design supercapacitor with pseudocapacitive electrodes of carbon and oxides of iron, manganese, cobalt, vanadium, ruthenium, tungsten, nickel, and mixed metals for the enhanced electrochemical properties . For carbon composites synthesis chemistry, activating agents (e. g. ZnCl 2 , KOH, H 3 PO 4 , K 2 CO 3 ) are used to enhance the surface area, unique porosities, and activity which add few extra steps in the synthesis procedure.…”

“…For carbon composites synthesis chemistry, activating agents (e. g. ZnCl 2 , KOH, H 3 PO 4 , K 2 CO 3 ) are used to enhance the surface area, unique porosities, and activity which add few extra steps in the synthesis procedure. Among different transition metal, being abundant, low cost and having high theoretical capacitance, oxides of iron have gained widespread attention and have been explored as an electrode material due to its multiple valence states, rich redox pairs, high theoretical capacitance, natural abundance, low cost, and environmentally friendliness . The positive synergic coupling effects between the Fe x O y H z and carbon are superintended for its superior properties related to the energy storage applications .…”

Partially Graphitized Iron-Carbon Hybrid Composite as Electrochemical Supercapacitor Material

“…In the field of mesoporous materials, carbon-based functional materials represent the most investigated electrode materials for energy storage applications due to their excellent electrochemical activity as well as other advantages, including low costs and environmental friendliness. 1 A gazillions of strategies have been attempted by choosing different precursors to design supercapacitor with pseudocapacitive electrodes of carbon and oxides of iron, 4-8 manganese, 9 cobalt 10 , vanadium, 11 ruthenium, 12 tungsten, 13 nickel 14 and mixed metals [15][16][17][18][19] for the enhanced electrochemical properties. 4 For carbon composite chemistry, activating agents (e.g ZnCl2, KOH, H3PO4, K2CO3) are used to enhance the surface area, unique porosities and activity which add an extra step in synthesis.…”

“…Na2SO4 for spindle-like carbon incorporated-Fe2O3 grown on carbon nanotube fiber in a three-electrode system. 15 Recently, the carbon derived from biomass especially biowaste, has sparked tremendous interest in the energy material research. The potential candidacy of the biowaste derived carbon is primarily due to the inexpensiveness, sustainability, abundance, and environmental friendliness of the raw materials, as well as the high performance of the resultant carbon.…”