Fabrication of Hierarchical Porous Metal–Organic Framework Electrode for Aqueous Asymmetric Supercapacitor

Abstract

As promising electrode materials in supercapacitors, metal–organic frameworks (MOFs) have attracted significant attention. However, the poor electrical conductivity and the almost exclusively microporous structure largely limited the possibility for MOFs to fabricate high-performance electrodes of supercapacitors. To overcome these obstacles, hierarchical porous Zr-MOFs (HP-UiO-66) has been successfully fabricated using bimetallic Zn/Zr MOFs as a precursor, subsequently wiping off Zr-MOFs. When used as electrode materials for supercapacitors, under a current density of 0.2 A g–1, the specific capacitance of the prepared HP-UiO-66 is 849 F g–1, which is 8.36 times higher than the 101.5 F g–1 of bare UiO-66. The clearly enhanced electrochemical performance of HP-UiO-66 was benefited from the advantages of the hierarchical porous structure, the higher specific surface area and pore volume, as well as the sufficient surface defects. Furthermore, an aqueous asymmetric supercapacitor based on the HP-UiO-66 and porous carbon could show an energy density of 32 W h kg–1 at a power density of 240 W kg–1. This strategy may offer a versatile idea of tailoring new type of MOFs and opens the possibility of MOFs using in the future high-energy storage device.

Porosity Engineering of MOF‐Based Materials for Electrochemical Energy Storage

“…[174] Pore Size Distribution: Aside from SSAs, the PSD serves as another critical parameter that substantially affects the performance. [170,[175][176][177] From the previous experience, [20] MOFs with dominant micropores are not suitable for high-performance charge storage because of retarded mass transfer. An indium-based mesoporous MOF (i.e., 437-MOF) has been used for investigation.…”

“…A critical challenge encountered by MOF-based supercapacitors resides in the low electrical conductivity of MOFs, which leads to a large resistance that causes serious energy loss (from a large iR drop) and poor rate performance. Therefore, most studies have fabricated electrodes by mixing MOFs www.advancedsciencenews.com with a considerable amount of conductive additives (typically 15−30% acetylene black or Super P [169,170] ), raising the cost and decreasing device-based gravimetric capacitance. To address this issue, some recent studies have devoted to promoting conductivity of MOFs by designing highly conjugated backbones.…”

MOF‐Derived Metal Oxide Composites for Advanced Electrochemical Energy Storage

“…Metal–organic frameworks (MOFs) are a novel type of crystalline porous material with a periodic network structure, which consists of inorganic vertices and organic linkers that are coupled to each other through coordination bonds . Among the emerging electrode materials, MOFs can be directly utilized as electrode materials for batteries and supercapacitors, due to their distinct advantages such as high specific surface area, controllable pore sizes, low densities, good thermal stability, and ordered crystal structure.…”

Room-Temperature Fabrication of a Nickel-Functionalized Copper Metal–Organic Framework (Ni@Cu-MOF) as a New Pseudocapacitive Material for Asymmetric Supercapacitors

“…According to the energy storage required for the application, there are two types of SCs formed from MOFs: (1) MOFs used as controlled templates or precursors for synthesizing mesoporous carbon, metal oxides, and metal sulfide via thermolysis or sulfurization [20,21,22,23,24,25,26], and (2) MOFs used as electroactive materials for SCs owing to their porous properties. To improve the electrochemical performance of MOFs, the supercapacitive properties of MOFs should be further evaluated [27,28,29,30].…”