Controlled thermolysis of MIL-101(Fe, Cr) for synthesis of FexOy/porous carbon as negative electrode and Cr2O3/porous carbon as positive electrode of supercapacitor

Kong

et al. 2019

Adv Elect Materials

nevertheless, they usually put undue emphasis on the capacity of the positive electrode, instead. There are few reports that discuss the negative electrode materials relatively. As a result, the capacity of the negative electrodes is much lower than that of the positive electrodes, and the capacity mismatch between the positive and negative electrodes is more serious. [6] As a matter of fact, similar to "cask effect," the capacity of the negative electrode is the shortest plank for supercapacitor, which decides how much energy capacity the supercapacitor can store. In other words, the way that can increase the capacity of the negative electrode materials, can remedy the low energy density deficiency of supercapacitor. [7] Looking at what predecessors have been developed for constructing the supercapacitor negative electrode, carbon and Fe-based materials are two major electrodes that can be utilized. [8][9][10] Due to the redox characteristic of Fe-based materials, it is believed to have the higher theoretical capacity compared with carbon materials that presents double layer capacitance characteristics. [11] To our disappointment, the poor electrical conductivity, which affects the efficiency of electronic transmission, resulted in low supercapacitor performance embodiment, far less than what was expected. [12,13] Therefore, how to improve the electrical conductivity to enhance the efficiency of electron transfer is the most important factor when designing and fabricating an Fe-based negative electrode material. [14] To address this challenge, one of the strategies is to fabricate composites with carbon materials. [4,15] On account of the excellent electrical conductivity of carbon materials, the Fe-based compand/carbon composites show good electrical conductivity. However, the low theoretical capacity of carbon materials limits the capacity promotion of Fe-based compand/ carbon composites. Another method is to rationally design a hierarchical nanostructure. [5,14,16,17] Core-shell structure is believed to be a good choice, where materials with good electrical conductivity are used as the core and materials with high theoretical capacity are used as the shell. [13,[18][19][20] Therefore, the good electrochemical performance has been ascribed to its unique structure, which endows the electrode with large specific area and facilitates the contact between the electrode and The shortcoming of Fe-based materials, their poor electron transfer efficiency, restricts their electrochemical performance severely. An electric field (E) is induced by an Fe 7 S 8 /α-FeOOH nano-heterostructure (SACF) via two simple immersion steps at room temperature. The charge transfer from α-FeOOH to Fe 7 S 8 spontaneously establishes an intrinsic electric field at the Fe 7 S 8 /α-FeOOH nano-heterostructure boundary. Additionally, the relationship between structure and property is investigated by structural characterization and density functional theory calculations that are used to explain the electron transfer mechanism and good wettabilit...

Section: Resultssupporting

confidence: 86%

Section: Wwwadvelectronicmatdesupporting

confidence: 88%

Electric‐Field‐Assisted Enhanced Electron Transfer to Boost Supercapacitor Negative Electrode Performance for a Fabricated Fe₇S₈/α‐FeOOH Nano‐Heterostructure

Kong

et al. 2019

Adv Elect Materials

“…Moradi et al reported a new ASC of Cr 2 O 3 /C//Fe x O y /C to overcome the limitations of general metal-oxide-based electrodes, such as low conductivity and inferior cycling and rate performance [193]. The MIL-101 (Fe) was hydrothermally synthesized using Cr (NO 3 ) 2 •9H 2 O, H 2 bdc, and 40% HF at 220 • C (8 h).…”

Section: Other Kindsmentioning

confidence: 99%

“…Interestingly, the surfaces of CoNi alloy NPs could be partially transformed into electrochemically active sites in an alkaline Figure 14. Ragone plots of Cr 2 O 3 /C//Fe x O y /C and other metal oxide/carbon composite-based ASCs [193].…”

Section: Composites Containing Co9s8mentioning

confidence: 99%

Porous Carbon-Based Supercapacitors Directly Derived from Metal–Organic Frameworks

Kim

Huh

2020

Materials

Numerously different porous carbons have been prepared and used in a wide range of practical applications. Porous carbons are also ideal electrode materials for efficient energy storage devices due to their large surface areas, capacious pore spaces, and superior chemical stability compared to other porous materials. Not only the electrical double-layer capacitance (EDLC)-based charge storage but also the pseudocapacitance driven by various dopants in the carbon matrix plays a significant role in enhancing the electrochemical supercapacitive performance of porous carbons. Since the electrochemical capacitive activities are primarily based on EDLC and further enhanced by pseudocapacitance, high-surface carbons are desirable for these applications. The porosity of carbons plays a crucial role in enhancing the performance as well. We have recently witnessed that metal–organic frameworks (MOFs) could be very effective self-sacrificing templates, or precursors, for new high-surface carbons for supercapacitors, or ultracapacitors. Many MOFs can be self-sacrificing precursors for carbonaceous porous materials in a simple yet effective direct carbonization to produce porous carbons. The constituent metal ions can be either completely removed during the carbonization or transformed into valuable redox-active centers for additional faradaic reactions to enhance the electrochemical performance of carbon electrodes. Some heteroatoms of the bridging ligands and solvate molecules can be easily incorporated into carbon matrices to generate heteroatom-doped carbons with pseudocapacitive behavior and good surface wettability. We categorized these MOF-derived porous carbons into three main types: (i) pure and heteroatom-doped carbons, (ii) metallic nanoparticle-containing carbons, and (iii) carbon-based composites with other carbon-based materials or redox-active metal species. Based on these cases summarized in this review, new MOF-derived porous carbons with much enhanced capacitive performance and stability will be envisioned.

“…To ensure the sensitivity of the electrochemical sensor, various functional nanomaterials are usually employed for signal amplification [13][14][15]. As one of the research hotspots in recent years, metal-organic frameworks (MOFs) have been used in many fields, such as catalysis [16], supercapacitors [17], adsorption and separation [18], and sensing [19][20][21]. Tang and coworkers have developed a series of MOF-based Immunosensors for fluorescent or colorimetric determination [22,23].…”

Section: Introductionmentioning

confidence: 99%

An Electrochemical Sensor for the Detection of Cu²⁺ Based on Gold Nanoflowers‐modifed Electrode and DNAzyme Functionalized Au@MIL‐101 (Fe)

Dai

et al. 2019

Electroanalysis

The cover picture shows the scheme of the electrochemical sensor for the detection of Cu2+ based on gold nanoflowers‐modifed electrode and DNAzyme functionalized Au@MIL‐101 (Fe). DNAzyme substrate strand was cleaved into two parts due to the presence of Cu2+, the oligonucleotide fragment linked to MIL‐101(Fe) was able to hybridize with DNA1 adsorbed onto the surface of AuNFs/ITO, so as to generate electrochemical signals' change. The electrochemical biosensor showed a sensitive detection range and a high selectivity. More Details can be found in the Full Paper by Shengpan Xu, Benlin Dai, Jiming Xu, Ling Jiang, and He Huang (DOI: 10.1002/elan.201900343).