Showing papers by "Jeonghun Kim published in 2019"
TL;DR: Insightful insights gathered in the process of studying TMS are provided, and valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies are described.
Abstract: Heterogenous electrocatalysts based on transition metal sulfides (TMS) are being actively explored in renewable energy research because nanostructured forms support high intrinsic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, it is described how researchers are working to improve the performance of TMS-based materials by manipulating their internal and external nanoarchitectures. A general introduction to the water-splitting reaction is initially provided to explain the most important parameters in accessing the catalytic performance of nanomaterials catalysts. Later, the general synthetic methods used to prepare TMS-based materials are explained in order to delve into the various strategies being used to achieve higher electrocatalytic performance in the HER. Complementary strategies can be used to increase the OER performance of TMS, resulting in bifunctional water-splitting electrocatalysts for both the HER and the OER. Finally, the current challenges and future opportunities of TMS materials in the context of water splitting are summarized. The aim herein is to provide insights gathered in the process of studying TMS, and describe valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies.
899 citations
TL;DR: The applications of these hollow structures as electrode materials for lithium-ion batteries, hybrid supercapacitors, and electrocatalysis are presented and an outlook on the emergent challenges and future developments in terms of their controllable fabrications and electrochemical applications is further discussed.
Abstract: Hollow materials derived from metal-organic frameworks (MOFs), by virtue of their controllable configuration, composition, porosity, and specific surface area, have shown fascinating physicochemical properties and widespread applications, especially in electrochemical energy storage and conversion. Here, the recent advances in the controllable synthesis are discussed, mainly focusing on the conversion mechanisms from MOFs to hollow-structured materials. The synthetic strategies of MOF-derived hollow-structured materials are broadly sorted into two categories: the controllable synthesis of hollow MOFs and subsequent pyrolysis into functional materials, and the controllable conversion of solid MOFs with predesigned composition and morphology into hollow structures. Based on the formation processes of hollow MOFs and the conversion processes of solid MOFs, the synthetic strategies are further conceptually grouped into six categories: template-mediated assembly, stepped dissolution-regrowth, selective chemical etching, interfacial ion exchange, heterogeneous contraction, and self-catalytic pyrolysis. By analyzing and discussing 14 types of reaction processes in detail, a systematic mechanism of conversion from MOFs to hollow-structured materials is exhibited. Afterward, the applications of these hollow structures as electrode materials for lithium-ion batteries, hybrid supercapacitors, and electrocatalysis are presented. Finally, an outlook on the emergent challenges and future developments in terms of their controllable fabrications and electrochemical applications is further discussed.
350 citations
TL;DR: Although porous materials based on coordination compounds, including metal-organic frameworks (MOFs) and porous coordination polymers (PCPs), have well-defined pore structures and promising propert...
Abstract: Although porous materials based on coordination compounds, including metal-organic frameworks (MOFs) and porous coordination polymers (PCPs), have well-defined pore structures and promising propert...
235 citations
TL;DR: In this paper, a metal-organic framework (MOF)/polypyrrole (PPy) hybrid was proposed for capacitive deionization (CDI) electrodes, in which conductive PPy nanotubes that are running through each MOF particle have the potential to increase the overall bulk electrical conductivity.
Abstract: New families of materials that may potentially replace dominant carbon electrodes have emerged as a major research hotspot in the field of capacitive deionization (CDI). Here, we report a metal–organic framework (MOF)/polypyrrole (PPy) hybrid, in which conductive PPy nanotubes that are running through each MOF particle have the potential to increase the overall bulk electrical conductivity, thus promoting such a system as a good CDI electrode material. Consequently, the MOF/PPy hybrid shows a high desalination capacity of 11.34 mg g−1, which is amongst those of state-of-the-art CDI electrodes. Moreover, the MOF/PPy hybrid also shows a superior desalination performance for brackish water and good cycling stability, far exceeding typical carbon-based benchmarks. This is the first example of CDI electrodes derived from direct MOF-based materials, highlighting the potential of these hybrid systems as promising materials beyond traditional carbon electrodes.
210 citations
TL;DR: The state-of-the-art research on pristine MOFs, MOFs composites, and their derivatives, such as oxides, metal/carbon hybrids, and carbon materials, is summarized and will hopefully promote the future development of MOFs-based materials toward SR-AOPs applications.
Abstract: With the ever-growing environmental issues, sulfate radical (SO )-based advanced oxidation processes (SR-AOPs) have been attracting widespread attention due to their high selectivity and oxidative potential in water purification. Among various methods generating SO , employing heterogeneous catalysts for activation of peroxymonosulfate or persulfate has been demonstrated as an effective strategy. Therefore, the future advances of SR-AOPs depend on the development of adequate catalysts with high activity and stability. Metal-organic frameworks (MOFs) with large surface area, ultrahigh porosity, and diversity of material design have been extensively used in heterogeneous catalysts, and more recently, enormous effort has been made to utilize MOFs-based materials for SR-AOPs applications. In this work, the state-of-the-art research on pristine MOFs, MOFs composites, and their derivatives, such as oxides, metal/carbon hybrids, and carbon materials for SR-AOPs, is summarized. The mechanisms, including radical and nonradical pathways, are also detailed in the discussion. This work will hopefully promote the future development of MOFs-based materials toward SR-AOPs applications.
205 citations
TL;DR: Understanding how mesoporous noble metal architectures affect electrocatalytic performance is very important for the rational design and preparation of high-performance electrocatalyststs.
Abstract: Understanding how mesoporous noble metal architectures affect electrocatalytic performance is very important for the rational design and preparation of high-performance electrocatalysts. Herein, by using polymeric micelle-assembled structures as templates, mesoporous Pd nanoparticles with tunable porous constructions are synthesized by simply tuning the solvent compositions. The effect of porous Pd nanoparticles on the electrocatalytic performance is thoroughly studied. Their superior electrocatalytic activity can be attributed to the mass transport efficiency and open porous structures.
161 citations
TL;DR: The synthesis of hollow microspherical and microtubular carbazole-based COFs through template-free, one-pot, [3 + 3] condensations of the novel triamine 9-(4-aminophenyl)-carbazoles-3,6-diamine (Car-3NH2) and triformyl linkers with various degrees of planarity are reported.
Abstract: Covalent organic frameworks (COFs) are a family of crystalline porous networks having applications in various fields, including gas and energy storage. Despite respectable progress in the synthesis of such crystalline materials, examples of the use of template-free methods to construct COFs having hollow nano- and microstructures are rare. Furthermore, all reported methods for synthesizing these hollow structural COFs have involved [4 + 2] and [3 + 2] condensations. Herein, we report the synthesis of hollow microspherical and microtubular carbazole-based COFs through template-free, one-pot, [3 + 3] condensations of the novel triamine 9-(4-aminophenyl)-carbazole-3,6-diamine (Car-3NH2) and triformyl linkers with various degrees of planarity. Depending upon the monomer's planarity, a unique morphological variety was observed. A time-dependent study revealed that each COF formed through an individual mechanism depended on the degree of planarity of the triformyl linker; it also confirmed that the hollow structures of these COFs formed through inside-out Ostwald ripening. Our COFs exhibited high Brunauer-Emmett-Teller surface areas (up to ca. 1400 m2 g-1), excellent crystallinity, and high thermal stability. Moreover, the CO2 uptake capacities of these COFs were excellent: up to 61 and 123 mg g-1 at 298 and 273 K, respectively. The high surface areas facilitated greater numbers of strong interactions with CO2 molecules, leading to high CO2 uptake capacities. Moreover, the prepared COFs exhibited redox activity because of their redox-active triphenylamine and pyridine groups, which can be utilized in electrochemical energy storages. Accordingly, such hollow COFs having high surface areas appear to be useful materials for industrial and biological applications.
154 citations
TL;DR: In this paper, a review of the development of nanoporous Fe-N/C electrocatalysts for oxygen reduction reaction (ORR) is presented, and the challenges and perspectives with respect to future development of highly active nanoporic Fe-n/C electrodes are discussed.
Abstract: Polymer electrolyte membrane fuel cells (PEMFCs) are one of the most sustainable energy conversion systems because of their high energy conversion efficiency and low/zero emissions. Unfortunately, the utilization of highly active but costly platinum (Pt)-based electrocatalysts is necessary to accelerate the sluggish kinetics of cathodic oxygen reduction in PEMFCs for practical applications. Under such circumstance, enormous efforts have been devoted to the exploration of inexpensive and earth-abundant non-noble metal-based electrocatalysts to replace or reduce the usage of Pt-based electrocatalysts in the past decades. Heteroatom-doped carbon materials are among some of the most promising non-noble metal-based electrocatalysts, especially transition metal- and nitrogen-doped carbon materials. According to previous findings, iron- and nitrogen-doped carbon (Fe-N/C) materials derived using various methodologies showed outstanding electrocatalytic activity and impressive durability. Therefore, tremendous progress has been achieved in the synthesis of Fe-N/C and the identification of active sites for oxygen reduction reaction (ORR). Creating ORR active sites, such as Fe-Nx, N/C, and Fe3C@C moieties, increasing the density of active sites and improving the utilization efficiency of ORR active sites are considered as the most effective steps for enhancing the ORR performance of Fe-N/C electrocatalysts. The creation of nanoporous structure of Fe-N/C electrocatalysts plays critical roles in increasing the number of ORR active sites and exposing abundant accessible ORR active sites to electrolytes. In addition, the interconnected nanopores facilitate the mass transfer of reactants and products inside the carbon matrix during the ORR reactions. Therefore, this review pays specific attention to the design and synthetic strategies of Fe-N/C materials with porous structures and their merits toward ORR. Finally, based on the construction of nanoporous structures, the challenges and perspectives with respect to future development of highly active nanoporous Fe-N/C electrocatalysts are discussed.
146 citations
TL;DR: An overview of the recent developments in the field of SAMs is provided with a particular emphasis on the reaction scope and advantages of heterogeneous solid acid catalysts.
Abstract: Sulfonic acid based mesostructures (SAMs) have been developed in recent years and have important catalytic applications. The primary applications of these materials are in various organic synthesis reactions, such as multicomponent reactions, carbon-carbon bond couplings, protection reactions, and Fries and Beckman rearrangements. This review aims to provide an overview of the recent developments in the field of SAMs with a particular emphasis on the reaction scope and advantages of heterogeneous solid acid catalysts.
127 citations
TL;DR: In this article, a 3D graphene hydrogel (FePGH) was used as an electrocatalyst for robust CO2 reduction to CO. The results showed that FePGH showed considerable catalytic durability maintaining a consistent CO yield (96.4% FE) over 20 h electrolysis at the same overpotential, corresponding to the highest cathodic energy efficiency yet observed.
Abstract: Although electrochemical CO2 reduction is one of the most promising ways to convert atmospheric CO2 into value-added chemicals, there are still numerous limitations to overcome to achieve highly efficient CO2 conversion performance. Herein, we report for the first time the development and use of a three-dimensional iron porphyrin-based graphene hydrogel (FePGH) as an electrocatalyst for extremely efficient robust CO2 reduction to CO. Electrocatalytic CO2 conversion was performed in aqueous medium with FePGH, which has a highly porous and conductive 3D graphene structure, resulting in high catalytic activity for CO production with ∼96.2% faradaic efficiency at a very low overpotential of 280 mV. Furthermore, FePGH showed considerable catalytic durability maintaining a consistent CO yield (96.4% FE) over 20 h electrolysis at the same overpotential, corresponding to the highest cathodic energy efficiency yet observed of 79.7% compared to other state-of-the-art immobilised metal complex electrocatalysts. This approach to fabricating a 3D graphene-based hydrogel electrocatalyst should provide an exciting new avenue for the development of other kinds of molecular electrocatalysts.
107 citations
TL;DR: In this paper, the authors demonstrate a facile strategy to synthesize 1D hollow carbon nanofibers (HCNFs) in a scalable manner, and a catalytic device was then constructed to explore the potential applications of HCNFs.
Abstract: Carbon materials, especially N-doped carbon materials with a one-dimensional (1D) hollow structure, have attracted great attention as one of the most efficient and eco-friendly catalysts for advanced oxidation processes (AOPs). The complex synthesis process of 1D hollow carbon however remains a major challenge in meeting the growing demand for it as a superior carbon-based catalyst. Herein, we demonstrate a facile strategy to synthesize 1D hollow carbon nanofibers (HCNFs) in a scalable manner. In this study, zeolitic imidazolate framework-8 (ZIF-8)/polyacrylonitrile (PAN) fibers were fabricated via electrospinning, and subsequent pyrolysis of the as-prepared ZIF-8/PAN composite nanofibers produced HCNFs. With excellent structural advantages and N-doped composition, HCNFs exhibited a remarkable level of catalytic degradation of tetracycline (TC) in the peroxymonosulfate (PMS) activation system. Furthermore, the HCNFs also showed good mechanical flexibility. A catalytic device was then constructed to explore the potential applications of HCNFs.
TL;DR: The nucleophilic addition reaction of aromatic carbonyl compounds (ACCs) is first used to explain the electrochemical behavior of carbonyL compounds during charge–discharge, and the relationship of the molecular structure and electrochemical properties of ACCs are discussed.
Abstract: To sustainably satisfy the growing demand for energy, organic carbonyl compounds (OCCs) are being widely studied as electrode active materials for batteries owing to their high capacity, flexible structure, low cost, environmental friendliness, renewability, and universal applicability. However, their high solubility in electrolytes, limited active sites, and low conductivity are obstacles in increasing their usage. Here, the nucleophilic addition reaction of aromatic carbonyl compounds (ACCs) is first used to explain the electrochemical behavior of carbonyl compounds during charge-discharge, and the relationship of the molecular structure and electrochemical properties of ACCs are discussed. Strategies for molecular structure modifications to improve the performance of ACCs, i.e., the capacity density, cycle life, rate performance, and voltage of the discharge platform, are also elaborated. ACCs, as electrode active materials in aqueous solutions, will become a future research hotspot. ACCs will inevitably become sustainable green materials for batteries with high capacity density and high power density.
TL;DR: Recent important approaches for advanced MOF-derived carbon structures with a focus on precursor control, heteroatom doping, shape/orientation control, and hybridization with other functional materials are introduced.
Abstract: Metal-organic framework (MOF)-derived nanoporous carbon materials have attracted significant interest due to their advantages of controllable porosity, good thermal/chemical stability, high electrical conductivity, catalytic activity, easy modification with other elements and materials, etc. Thus, MOF-derived carbons have been used in numerous applications, such as environmental remediations, energy storage systems (i.e. batteries, supercapacitors), and catalysts. To date, many strategies have been developed to enhance the properties and performance of MOF-derived carbons. Herein, we introduce and summarize recent important approaches for advanced MOF-derived carbon structures with a focus on precursor control, heteroatom doping, shape/orientation control, and hybridization with other functional materials.
TL;DR: Recent advances in the preparation of Pd-based nanoarchitectures through solution-phase chemical reduction and electrochemical deposition methods are summarized.
Abstract: Palladium (Pd) plays an important role in numerous catalytic reactions, such as methanol and ethanol oxidation, oxygen reduction, hydrogenation, coupling reactions, and carbon monoxide oxidation. Creating Pd-based nanoarchitectures with increased active surface sites, higher density of low-coordinated atoms, and maximized surface coverage for the reactants is important. To address the limitations of pure Pd, various Pd-based nanoarchitectures, including alloys, intermetallics, and supported Pd nanomaterials, have been fabricated by combining Pd with other elements with similar or higher catalytic activity for many catalytic reactions. Herein, recent advances in the preparation of Pd-based nanoarchitectures through solution-phase chemical reduction and electrochemical deposition methods are summarized. Finally, the trend and future outlook in the development of Pd nanocatalysts toward practical catalytic applications are discussed.
TL;DR: In this article, a nanoporous cellulose paper-based SERS platform was developed to analyze multiplex hazardous pesticides including thiram (T1), tricyclazole (T2), and carbaryl (C) by surface enhanced Raman scattering (SERS).
Abstract: In this study, a nanoporous cellulose paper-based SERS platform was developed to analyze multiplex hazardous pesticides including thiram (T1), tricyclazole (T2), and carbaryl (C) by surface enhanced Raman scattering (SERS). Gold nanorods (AuNRs) with different aspect ratios were synthesized and compared to achieve the highest SERS signals on paper-based SERS substrates. The advantage of the nanoporous cellulose nanofiber (CNF) matrix with nanoscale surface roughness is that it allows actual nanofiltration, resulting in a uniform and well-controlled AuNR distribution on the top portion of the CNF matrix. The as-prepared CNF–AuNR-based SERS platform exhibited an enhancement factor of 1.4 × 107 as well as the ability to simultaneously detect T1, T2, and C at concentrations as low as 1 nM, 100 nM, and 1 μM, respectively. In addition to analyzing triplex pesticide mixtures in solution, the SERS platform allows for a paper-based SERS swab for rapid trace detection on real-world surfaces. The detection limits for T1, T2, and C residues in apple peels were 6, 60, and 600 ng cm−2, respectively, which are much lower than the maximum residue level requirement for apple peels (2000 ng cm−2). These results demonstrate that the low-cost, flexible, lightweight, paper-based SERS platform shows powerful potential for high SERS performance and on-site SERS analysis.
01 May 2019
TL;DR: In this paper, the recent advances in the preparation of various iron oxide nano-architectures are reviewed along with their functional applications in energy storage, biomedical, and environmental fields.
Abstract: Iron oxide nanoarchitectures with distinct morphologies from 1D to 3D have been developed using various wet chemical methods. They have been employed for a wide range of applications, including energy storage, biomedical, and environmental applications. The functional properties of iron oxide nanoarchitectures depend on the size, shape, composition, magnetic properties, and surface modification. To overcome the limitations of pure iron oxide nanostructures, hybridizations with various inorganic materials (e.g., silica, metals, metal oxides) and carbon-based materials have been proposed. Herein, the recent advances in the preparation of various iron oxide nanoarchitectures are reviewed along with their functional applications in energy storage, biomedical, and environmental fields. Finally, the effects of various parameters on the functional performance of iron oxide nanostructures for these applications are summarized and the trends and future outlook on the development of iron oxide nanoarchitectures for these applications are also given.
25 Feb 2019
TL;DR: The development of this novel concept of room-temperature crystallization without the aid of additives and solvents represents a crucial breakthrough that is highly significant for exploring the green and energy-efficient synthesis of a variety of oxide and metal thin films.
Abstract: For the first time, this work presents a novel room temperature time-effective concept to manipulate the crystallization kinetics and magnetic responses of thin films grown on amorphous substrates. Conventionally, metal-induced crystallization is adopted to minimize the crystallization temperature of the upper-layer thin film. However, due to the limited surface area of the continuous metal under-layer, the degree of crystallization is insufficient and post-annealing is required. To expose a large surface area of the metal under-layer, we propose a simple and novel approach of using an Au nanodots array instead of a continuous metallic under-layer to obtain crystallization of upper-layer thin films. Spinel cobalt ferrite (CFO) thin film as a 'model' was deposited on an Au nano-dots array to realize this methodology. Our findings revealed that the addition of quantum-sized Au nano-dots as a metal under-layer dramatically enhanced the crystallization of the cobalt ferrite upper layer at room temperature. The appearance of major X-ray diffraction peaks with high intensity and well-defined crystallized lattice planes observed via transmission electron microscopy confirmed the crystallization of the CFO thin film deposited at room temperature on 4 nm-sized Au nano-dots. This crystallized CFO thin film exhibits 18-fold higher coercivity (Hc = 4150 Oe) and 4-fold higher saturation magnetization (Ms = 262 emu cm-3) compared to CFO deposited without the Au under-layer. The development of this novel concept of room-temperature crystallization without the aid of additives and solvents represents a crucial breakthrough that is highly significant for exploring the green and energy-efficient synthesis of a variety of oxide and metal thin films.
TL;DR: In this paper, an overview of recent advancement in the fabrication of piezoelectric devices for the interfacial mass sensing of targeted chemical vapors and ions through combination with nanoporous materials including mesoporous materials carbon-based nanomaterials, metal-organic frameworks (MOFs), MOF-derived nanoporous carbons, Prussian blue (PB) and its analogues (PBA), zeolites and related materials.
Abstract: Mass interfacial processes have been considered as one of the crucial factors supporting fundamental research. Due to the low cost and conceptual simplicity, significant advancements have been achieved in the development of methodologies based on piezoelectric devices for in situ determination of mass changes on the surfaces of deposited materials under various conditions. The introduction of nanomaterials for designing sensors and monitoring systems becomes essential to create advanced detection systems for selective sensing of toxic analytes for environmental remediation. The integration of materials with predesignated nanostructures into sensor devices, such as surface acoustic wave (SAW), quartz crystal microbalance (QCM), and QCM with dissipation (QCM-D) monitoring, has led to an immense progress in the sensing applications of toxic target analytes at the nanogram range. Here, an overview is introduced of recent advancement in the fabrication of piezoelectric devices for the interfacial mass sensing of targeted chemical vapors and ions through combination with nanoporous materials including mesoporous materials carbon-based nanomaterials, metal–organic frameworks (MOFs), MOF-derived nanoporous carbons, Prussian blue (PB) and its analogues (PBA), zeolites and related materials. Challenges and future prospect are also summarized by the advanced QCM technique associated with properties of nanostructured materials.
TL;DR: This review aims to provide a detailed glimpse of hard- and soft-templating approaches for future development of functional nanoporous carbon materials.
Abstract: Hard- and soft-templating approaches are one of potential strategies for the fabrication of functional nanoporous carbon materials with desired morphologies and properties. Enormous efforts have been paid for understanding the synthetic mechanisms that strongly influence the materials design and applications. All of these investigations are crucial to encourage the application of hard- and soft-templating approaches for the precise synthesis of nanoporous carbon materials. In this review, we mainly summarize significant works employing different synthetic methods for making carbon materials with various pore sizes and functionalities. The content of the review article contains: (i) Hard-templating synthesis of microporous carbon from zeolites; (ii) Hard-templating synthesis of mesoporous carbon from mesoporous silica; (iii) Hard-templating synthesis of macroporous carbon; and (iv) Soft-templating synthesis of mesoporous carbon. This review aims to provide a detailed glimpse of hard- and soft-templating approaches for future development of functional nanoporous carbon materials.
TL;DR: This in-depth study of crystal structure based nanozyme activity will guide designing highly effective nanozymes based on iron oxide nanostructures for chemical sensing, biosensing and environmental remediation.
Abstract: Nanozymes (nanoparticles with enzyme-like properties) have attracted considerable attention in recent years owing to their intrinsic enzyme-like properties and broad application in the fields of ELISA based immunoassay and biosensing. Herein, we systematically investigate the influence of crystal phases (γ-Fe2O3 and α-Fe2O3) of mesoporous iron oxide (IO) on their peroxidase mimetic activity. In addition, we have also demonstrated the applicability of these mesoporous IOs as nanozymes for detecting the glucose biomarker with a limit of detection (LOD) of 0.9 μM. Mesoporous γ-Fe2O3 shows high nanozyme activities (and magnetism) toward the catalytic oxidation of chromogenic substances, such as 3,3',5,5'-tetramethylbenzidine (TMB) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)-ABTS, as well as for the colourimetric detection of glucose, compared to that of α-Fe2O3. We believe that this in-depth study of crystal structure based nanozyme activity will guide designing highly effective nanozymes based on iron oxide nanostructures for chemical sensing, biosensing and environmental remediation.
TL;DR: It is demonstrated that the temperature increase on PEDOT:PSS/agarose via photothermal conversion resulted in the rapid and effective killing of nearly 100% of the pathogenic bacteria within 2 min of NIR irradiation.
TL;DR: In this article, the authors reported the synthesis of nanoporous carbons (NCs) derived from a low-cost and renewable biomass, jute, by a chemical activation process using KOH.
01 Nov 2019
TL;DR: Various advanced strategies for developing MOF‐based biocomposites for a wide range of bioapplications, such as biomedical storage, tumor cell targeting, and drug delivery are covered.
Abstract: The formation of biofunctionalized metal–organic frameworks (MOFs) by growing them on a variety of macromolecular biological species, particularly on enzymes and living cells, offers exciting opportunities for a wide range of applications, including biocatalysis, biosensing, and diagnoses MOFs are commonly subjected to biofunctionalization and biomimetic mineralization, owing to their good chemical and thermal stabilities and easy preparation in aqueous medium under ambient conditions The functionalization of MOFs with biological substances, such as enzymes, nonenzymatic proteins, and living cells promotes the formation of MOF‐based biocomposites which retain the biological functions of the embedded biological substances The most common method to construct these biofunctionalized MOFs is either by directly growing the MOF on the biological moiety or by postsynthetic modification of the exterior surface of the MOF with the desired biological species In particular, hierarchically porous MOFs (containing both mesopores and micropores) are ideal candidates for hosting enzymes and for the translocation of nonenzymatic proteins This review covers various advanced strategies for developing MOF‐based biocomposites for a wide range of bioapplications, such as biomedical storage, tumor cell targeting, and drug delivery The influence of MOFs on the biological activity of living cells and future prospects for developing novel MOF‐based biorefinery are discussed
TL;DR: In this article, a soft-templating method was developed to synthesize mesoporous nanosheets via solution-based assembly of close-packed polymeric micelles in the presence of metal precursors and reducing agents.
TL;DR: Density functional theory calculations reveal that Zn, N co-doping can synergistically weaken the strong Mo-H bonding, improve absorbed hydrogen atom (Hads) desorption and lead to faster HER kinetics.
Abstract: Developing non-precious metal catalysts with both high efficiency and long-term stability is the top priority for hydrogen evolution reactions (HER). Herein, we present a facile two-step method to synthesize Zn, N co-doped molybdenum carbide nanosheets (Zn-N-MoC-H NSs) by using bi-metal oxides of ZnMoO4 as a unique precursor. Zn not only serves as a template to form a porous structure on MoC nanosheets during volatilizing at high temperatures, but also acts as a doping source for Zn doping in MoC. The N-containing carbon source realizes N doping of MoC. Benefitting from Zn, N co-doping and the porous nanosheet structure with a large electrochemical surface area, Zn-N-MoC-H NSs lead to enhanced HER activity in an acidic electrolyte (0.5 M H2SO4) with a low onset potential of -66 mV vs. RHE (1 mA cm-2), overpotential of 128 mV (10 mA cm-2), small Tafel slope of 52.1 mV dec-1 and persistent long-term stability. Density functional theory calculations reveal that Zn, N co-doping can synergistically weaken the strong Mo-H bonding, improve absorbed hydrogen atom (Hads) desorption and lead to faster HER kinetics. This study provides new insights into the use of Zn as a template and electronic regulator toward efficient catalysis and applications in energy storage and conversion.
TL;DR: The highly conductive PEDOT:PSS/CNF porous nanocomposite papers with excellent flexibility described here are potential candidates for application in porous paper electrodes, flexible energy storage devices, and bioengineering sensors.
Abstract: In this paper, we report the fabrication of highly conductive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/cellulose nanofiber (CNF) nanocomposite paper with excellent flexibility through post-treatment with an organic solvent. The post-treated PEDOT:PSS/CNF porous nanocomposite papers showed a lower sulfur content, indicating the removal of residual PSS. The electrical conductivity of PEDOT:PSS/CNF porous nanocomposite paper was increased from 1.05 S/cm to 123.37 S/cm and 106.6 S/cm by post-treatment with dimethyl sulfoxide (DMSO) and ethylene glycol (EG), respectively. These values are outstanding in the development of electrically conductive CNF composites. Additionally, the highly conductive nanocomposite papers showed excellent bending stability during bending tests. Cyclic voltammetry (CV) showed a Faradaic redox reaction and non-Faradaic capacitance due to the redox activity of PEDOT:PSS and large surface area, respectively. Electrochemical energy storage ability was evaluated and results showed that capacitance improved after post-treatment. We believe that the highly conductive PEDOT:PSS/CNF porous nanocomposite papers with excellent flexibility described here are potential candidates for application in porous paper electrodes, flexible energy storage devices, and bioengineering sensors.
01 Nov 2019
TL;DR: In this paper, electrostatic interactions are used to wrap polyhedra particles of zeolitic imidazolate frameworks with graphene oxide (GO) nanosheets to prepare the composite structure.
Abstract: Heterostructured materials are interesting because they may combine two or more material building blocks that together generate new types of heterointerfaces with unusual properties. Using them to construct large‐scale 3D frameworks further extends their utility in electrochemical applications because it exposes more interfaces and active sites. In this study, electrostatic interactions are used to wrap polyhedra particles of zeolitic imidazolate frameworks with graphene oxide (GO) nanosheets to prepare the composite structure. Pyrolyzing this structure generates a 3D porous carbon framework (PCF) composed of polyhedral‐shaped hollow carbon coated with reduced GO. The size of the polyhedral macropores can be adjusted from nanometer scale to micrometer scale. The PCFs generate a continuous network of heterostructured carbon with a large surface area and large pore volumes that are particularly useful as porous electrodes in lithium–sulfur batteries. The PCF/S composite electrode exhibits a high discharge capacity of 1151 mAh g−1 at 1 C and a low capacity decay of 0.035% per cycle after 650 cycles.
TL;DR: It has been observed that the porosities introduced into the bulk sample significantly improve the Seebeck coefficient and reduce the thermal conductivity by the charge carrier and phonon scattering respectively.
Abstract: Electron-doped SrTiO3 is a well-known n-type thermoelectric material, although the figure of merit of SrTiO3 is still inferior compared with p-type metal oxide-based thermoelectric materials due to...
TL;DR: In this article, dendritic platinum (Pt) nanoparticles are successfully anchored on Ketjen Black by a facile synthetic route without organic solvent, and the as-prepared catalyst shows an ideal four-electron pathway of O2 reduction to H2O and a low HO2 yield of less than 1% in the potential window of 0.2-0.8
TL;DR: In this article, a self-assembling Ni-based coordination polymers (Ni-CP) was proposed to self-assist in the self-assembly of graphene oxide (GO).