Currently, developing nonprecious‐metal catalysts to replace Pt‐based electrocatalysts in fuel cells has become a hot topic because the oxygen reduction reaction (ORR) in fuel cells often requires ...platinum, a precious metal, as a catalyst, which is one of the major hurdles for commercialization of the fuel cells. Recently, the newly emerging metal‐organic frameworks (MOFs) have been widely used as self‐sacrificed precursors/templates to fabricate heteroatom‐doped porous carbons. Here, the recent progress of MOF‐derived, heteroatom‐doped porous carbon catalysts for ORR in fuel cells is systematically reviewed, and the synthesis strategies for using different MOF precursors to prepare heteroatom‐doped porous carbon catalysts, including the direct carbonization of MOFs, MOF and heteroatom source mixture carbonization, and MOF‐based composite carbonization are summarized. The emphasis is placed on the precursor design of MOF‐derived metal‐free catalysts and transition‐metal‐doped carbon catalysts because the MOF precursors often determine the microstructures of the derived porous carbon catalysts. The discussion provides a useful strategy for in situ synthesis of heteroatom‐doped carbon ORR electrocatalysts by rationally designing MOF precursors. Due to the versatility of MOF structures, MOF‐derived porous carbons not only provide chances to develop highly efficient ORR electrocatalysts, but also broaden the family of nanoporous carbons for applications in supercapacitors and batteries.
Metal‐organic frameworks (MOFs) have emerged as promising precursors to synthesize metal‐free or nonprecious‐metal‐doped porous carbon catalysts for the oxygen reduction reaction (ORR) due to their unique advantages. Here, the recent progress of MOF‐derived carbon catalysts in ORR applications is systematically reviewed and the strategies to develop highly efficient carbon electrocatalysts by rationally designing MOF precursors are summarized.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Porous covalent-organic materials (COMs) are a fascinating class of nanoporous material with high surface area and diverse pore dimensions, topologies and chemical functionalities. These materials ...have attracted ever-increasing attention from different field scientists, owing to their potential applications in gas storage, adsorptive separation and photovoltaic devices. The versatile networks are constructed from covalent bonds (B-O, C-C, C-H, C-N, etc.) between the organic linkers by homo- or hetero-polymerizations. To design and synthesize novel porous COMs, we first summarize their synthesis methods, mainly including five kinds of coupling reaction, i.e.boronic acid, amino, alkynyl, bromine and cyan group-based coupling reactions. Then, we review the progress of porous COMs in clean energy applications in the past decade, including hydrogen and methane storage, carbon dioxide capture, and photovoltaic applications. Finally, to improve their gas adsorptive properties, four possible strategies are proposed, and high-capacity COMs for gas storage are designed by a multiscale simulation approach.
Rapid and selective sensing of sulfur dioxide (SO2) gas has attracted more and more attention because SO2 not only causes environmental pollution but also severely affects the health of human beings. ...Here we report an amino-functionalized luminescent metal–organic framework (MOF) material (i.e., MOF-5-NH2) and further investigate its sensing property for SO2 gas and its derivatives as a luminescent probe. The results indicate that the MOF-5-NH2 probe can selectively and sensitively sense SO2 derivatives (i.e., SO3 2–) in real time by a luminescence turn-on effect with a lower detection limit of 0.168 ppm and a response time of less than 15 s. Importantly, the luminescence turn-on phenomenon can be observed by the naked eye. We also assembled MOF-5-NH2 into a test paper to achieve the aim of portable detection, and the lower-limit concentration of the test paper for sensing SO2 in real time was found to be about 0.05 ppm. Moreover, MOF-5-NH2 also shows good anti-interference ability, strong luminescence stability, and reusability, which means that this material is an excellent sensing candidate. The amino functionalization may also provide a modification strategy to design luminescent sensors for other atmospheric pollutants.
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IJS, KILJ, NUK, PNG, UL, UM
Three porous luminescent covalent‐‐organic polymers (COPs) have been synthesized through self‐polycondensation of the monomers of tris(4‐bromophenyl)amine, 1,3,5‐tris(4‐bromophenyl)benzene, and ...2,4,6‐tris‐(4‐bromo‐phenyl)‐1,3,5triazine by using Ni‐catalyzed Yamamoto reaction. All the COP materials possess not only high Brunauer–Emmett–Teller (BET) specific surface area of about 2000 m2 g−1, high hydrothermal stability, but also graphene‐like layer texture. Interestingly, COP‐3 and COP‐4 show very fast responses and high sensitivity to the nitroaromatic explosives, and also high selectivity for tracing picric acid (PA) and 2,4,6‐trinitrotoluene (TNT) at low concentration (<1 ppm). In short, the COPs may be a new kind of material for detecting explosives and small organic molecules.
Three porous graphene‐like covalent–organic polymers (COPs) have been synthesized by Ni‐catalyzed Yamamoto reaction in this work. These COP materials show fast responses and high sensitivity to the nitroaromatic explosives. The COP materials may be a new candidate for detecting explosives.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To achieve wearable application, developing highly active and low cost non-precious metal bifunctional oxygen catalysts for foldable solid-state Zn-air battery is still a great challenge. Herein, we ...report a single-atom cobalt electrocatalyst with CoN4 moieties dispersed on nitrogen-doped graphitic nanosheet (marked as CoN4/NG) by a surfactant-assisted approach. The CoN4/NG catalyst exhibits excellent electrocatalytic activities with a half-wave potential of 0.87 V (versus RHE) for ORR and a low overpotential of 0.38 V at 10 mA cm−2 for OER. Moreover, the liquid Zn-air battery with the CoN4/NG catalyst as the air electrode displays a superior discharging and charging performance, larger power density, higher energy density and robust stability (without any decay after 100 h cycle test), compared to the 20% Pt/C + IrO2 counterpart. Importantly, the CoN4/NG-based flexible solid-state Zn-air battery also exhibits a high power density and a long-term stability of 30 cycles under flat and folded states, which means that the single-atom cobalt catalyst may be a promising candidate for practical applications in wearable flexible solid batteries.
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•We propose a surfactant-assisted approach to synthesize single-atom cobalt catalyst CoN4/NG.•The CoN4/NG catalysts shows excellent electrocatalytic activities for both ORR and OER.•Both the CoN4/NG-based liquid and solid Zn-air batteries exhibit a high power density and a long-term stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hydrogen evolution reaction (HER) is a key reaction in water splitting, and developing efficient and robust non‐noble electrocatalysts for HER is still a great challenge for large‐scale hydrogen ...production. Herein, a vertically aligned core–shell structure grown on Ti foil with CoP nanoarray as a core and N,P‐doped carbon (NPC) as a shell (CoP/NPC/TF) is first reported as an efficient electrocatalyst for HER. Results indicate that CoP/NPC/TF only demands the overpotentials of 91 and 80 mV to drive the current density of 10 mA cm−2 in acidic and alkaline solutions. The electrochemical measurements and theoretical calculations show that the synergy of CoP nanorod core and porous NPC shell enhances HER performance significantly, because the introduction of porous NPC shell not only offers more active sites but also improves the electrical conductivity and durability of the sample in acidic and alkaline solutions. Density functional theory calculation further reveals that all the C atoms between N and P atoms in CoP/NPC are the most efficient active sites, which greatly improve the HER performance. The identification of active species in this work provides an effective strategy to design and synthesize the low‐cost, high‐efficient, and robust CoP‐based electrocatalysts.
A vertical CoP nanoarray wrapped by N,P‐doped carbon (NPC) is first reported as a high‐efficient electrocatalyst for the hydrogen evolution reaction. The excellent performance of the catalyst is attributed to the synergistic effect of CoP and NPC. Density functional theory calculation reveals that the C atoms between N and P atoms are the most efficient active sites.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Non-precious metal and nitrogen codoped carbon catalysts have emerged as promising candidates to replace noble platinum (Pt)-based catalysts in the processes of the oxygen reduction reaction (ORR) ...and the hydrogen evolution reaction (HER). Herein, we use a 1D/2D hybrid strategy to synthesize a Co,N-codoped carbon nanotube (CNT)/graphene heterostructure bifunctional catalyst (Co/NCNT/NG). The Co/NCNT/NG heterostructure catalyst shows not only a positive half-wave potential of 0.85 V ( versus RHE) and long-term stability for the ORR, but also a low overpotential of 123 mV at a current density of 10 mA cm −2 and ultrahigh stability in 0.5 M H 2 SO 4 for the HER. The superior performance of the Co/NCNT/NG catalyst is attributed to the inimitable 1D/2D CNT/graphene heterostructure, in which 1D and 2D structures provide different catalytically active sites (including metallic Co, CoN 2 and N–C) for the HER and ORR, respectively. Moreover, the catalyst also exhibits similar discharge performance and robust durability as an air electrode in Zn–air batteries to the Pt-based one. This work provides a new approach for the in situ synthesis of bifunctional and multifunctional catalysts by integrating 1D/2D/3D materials with different catalytically active sites into one heterostructure.
It is still a grand challenge to develop a highly efficient nonprecious-metal electrocatalyst to replace the Pt-based catalysts for oxygen reduction reaction (ORR). Here, we propose a ...surfactant-assisted method to synthesize single-atom iron catalysts (SA-Fe/NG). The halfwave potential of SA-Fe/NG is only 30 mV less than 20% Pt/C in acidic medium, while it is 30 mV superior to 20% Pt/C in alkaline medium. Moreover, SA-Fe/NG shows extremely high stability with only 12 mV and 15 mV negative shifts after 5,000 cycles in acidic and alkaline media, respectively. Impressively, the SA-Fe/NG-based acidic proton exchange membrane fuel cell (PEMFC) exhibits a high power density of 823 mW cm−2. Combining experimental results and density-functional theory (DFT) calculations, we further reveal that the origin of high-ORR activity of SA-Fe/NG is from the Fe-pyrrolic-N species, because such molecular incorporation is the key, leading to the active site increase in an order of magnitude which successfully clarifies the bottleneck puzzle of why a small amount of iron in the SA-Fe catalysts can exhibit extremely superior ORR activity.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The vigorous development of electronic equipment and wireless communication make the concealment and harm of electromagnetic radiation increasingly prominent, which seriously affects the normal ...operation of electrical equipment. Therefore, it is momentous to evolve new electromagnetic interference (EMI) shielding materials with excellent comprehensive performances. In recent years, two-dimensional layered transition metal carbides, nitride or carbonitrides (MXenes), have received extensive attention in the EMI shielding field because of their outstanding electrical conductivity (σ), hydrophilicity and chemical activity. This review introduces the basic performances of MXenes as well as their precursor MAX. Subsequently, the influences of different precursor MAX and fabrication methods on the structures and properties of MXenes are summarized. Then it focuses on the preparation methods of MXenes and their MXenes/polymer EMI shielding composites and their latest research progress. Finally, the key scientific and technical problems to be solved urgently in MXenes and their MXenes/polymer EMI shielding composites are proposed, and the development trend of MXenes and their MXenes/polymer EMI shielding composites is prospected.
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•Different precursor MAX and fabrication methods influencing on the structures and properties of MXenes are summarized.•The research progress and preparation methods of MXenes/polymer EMI shielding composites are mainly summarized.•Key scientific problems to be solved urgently in MXenes and their MXenes/polymer EMI shielding composites are proposed.•Development trend of MXenes and their MXenes/polymer EMI shielding composites is prospected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Two-dimensional (2D) covalent organic polymers (COPs) and derivatives hold great potential for a large variety of applications, including gas storage, sensing, energy conversion and storage, and ...electrocatalysis. Moreover, 2D COPs offer excellent opportunities for fundamental study on an exciting class of new polymeric materials with unique 2D structures and novel properties. However, the design and synthesis of well-defined 2D COPs remain a big challenge. In this article, we review recent progress on 2D COPs and their derivatives. Some concepts on the rational design and syntheses of well-defined 2D COPs and their derivatives are discussed, along with their potential applications as well as the perspectives and challenges in this emerging field.
Recent developments in the design, synthesis and application of 2D covalent organic polymers are reviewed, along with some perspectives and challenges.
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