Self‐Assembled α‐Fe₂O₃ Mesocrystals/Graphene Nanohybrid for Enhanced Electrochemical Capacitors

Abstract

Self-assembled α-Fe2O3 mesocrystals/graphene nanohybrids have been successfully synthesized and have a unique mesocrystal porous structure, a large specific surface area, and high conductivity. Mesocrystal structures have recently attracted unparalleled attention owing to their promising application in energy storage as electrochemical capacitors. However, mesocrystal/graphene nanohybrids and their growth mechanism have not been clearly investigated. Here we show a facile fabrication of short rod-like α-Fe2O3 mesocrystals/graphene nanohybrids by self-assembly of FeOOH nanorods as the primary building blocks on graphene under hydrothermal conditions, accompanied and promoted by concomitant phase transition from FeOOH to α-Fe2O3. A systematic study of the formation mechanism is also presented. The galvanostatic charge/discharge curve shows a superior specific capacitance of the as-prepared α-Fe2O3 mesocrystals/graphene nanohybrid (based on total mass of active materials), which is 306.9 F g(-1) at 3 A g(-1) in the aqueous electrolyte under voltage ranges of up to 1 V. The nanohybrid with unique sufficient porous structure and high electrical conductivity allows for effective ion and charge transport in the whole electrode. Even at a high discharge current density of 10 A g(-1), the enhanced ion and charge transport still yields a higher capacitance (98.2 F g(-1)), exhibiting enhanced rate capability. The α-Fe2O3 mesocrystal/graphene nanohybrid electrode also demonstrates excellent cyclic performance, which is superior to previously reported graphene-based hematite electrode, suggesting it is highly stable as an electrochemical capacitor.

Microwave assisted fabrication of a nanostructured reduced graphene oxide (rGO)/Fe2O3 composite as a promising next generation energy storage material

“…13,[16][17][18][19][20][21]32 The specic capacitance for rGO/GCE and rGO-Fe 2 O 3 /GCE at a current density of 2 A g À1 is calculated to be 105 F g À1 and 577.5 F g À1 respectively, which is much higher than some of the earlier reports based on rGO/Fe 2 O 3 composition. [17][18][19][20][21]32 The rate performance of rGO/GCE and rGOFe 2 O 3 /GCE is also analyzed by plotting specic capacitance against current density. The specic capacitance kept on decreasing with increasing current density due to incomplete utilization of active ionic species at high current densities (Fig.…”

“…higher theoretical specic capacitance (1005 mA h g À1 ), facile synthetic approach, high corrosion resistance, earth-abundance, environmental friendliness and low processing cost. [18][19][20][21][22] However, Fe 2 O 3 alone as nanoparticles suffer from severe issues like low conductivity, high agglomeration and structural degradation during the charge and discharge cycling process which causes rapid loss of capacity caused by volume changes. 21 In this respect, highly thermal and electrically conductive graphene or rGO has been considered as the suitable support matrix for metal oxides to absorb the volume changes and to enhance the structural stability of the electrodes.…”

A High‐Energy Density Asymmetric Supercapacitor Based on Fe2O3 Nanoneedle Arrays and NiCo2O4/Ni(OH)2 Hybrid Nanosheet Arrays Grown on SiC Nanowire Networks as Free‐Standing Advanced Electrodes

“…An emerging new way to circumvent this vexing issue is to directly graft the electroactive Fe 2 O 3 onto conductive and robust skeletons, for example, graphene, carbon nanotubes, ordered multimodal porous carbon, and metal sulfide nanosheets to construct integrated hybrid electrode materials, which indeed shows relatively superior electrochemical properties than individual components due to the smart hybridization of the active materials and framework in synergy. [32][33][34][35][36] Despite much progress has been achieved by exploring various supporters, the trouble of unsatisfied energy storage capacity still exist in implementing the aforementioned composite as SC electrodes, probably because of the addition of polymer binder and conductive additive which unavoidably enhances the "dead" weight and impedes electron transfer, or the employment of press machine which causes the damage of structures of the active materials. Hence, there is an urgent need for searching for alternative suitable scaffolds for homogeneous distribution of the electroactive Fe 2 O 3 toward free-standing hybrid electrodes for high-performance SCs.…”

Urchin-like FeOOH hollow microspheres decorated with MnO2 for enhanced supercapacitor performance

“…Manganese dioxide (MnO 2 ) with favorable properties and high theoretical specific capacitance (1370 F g −1 ) makes it a promising electrode material in energy storage and conversion devices [26][27][28][29][30]. Furthermore, three-dimensional (3D) transitional metal oxides/ hydroxides nanostructures assembled from low-dimensional building blocks [31][32][33][34] exhibit enhanced properties compared to their bulk counterparts by offering a large specific surface area, high surface/body ratios, the enhanced permeability for the electrolyte ions, and rich electrochemically active sites [35]. Therefore, the construction of 3D FeOOH@MnO 2 is a rational way to realize a high performance EC.…”