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Researching of high performance and low-cost oxygen reduction reaction (ORR) electrocatalysts is one of the core issues for the rapid development of energy conversion and storage devices. Herein, a N and S dual-doped three-dimensional (3D) interconnected mesoporous carbon catalyst (CNS) was constructed via a facile hydrothermal-pyrolysis strategy. Benefiting from the 3D interconnected mesoporous architecture, CNS was endowed with a fast oxygen mass transfer rate together with plentiful of accessible active centers on the surface. Its ORR half-wave potential (E1/2， 0.87 V) surpasses commercial Pt/C catalyst 50 mV in alkaline media. Its E1/2 negatively shifts only 2 mV after 8000 cycles in half-cell tests. More importantly, the zinc-air battery with CNS as cathode catalyst delivers an excellent high peak power density of 144 mW cm−2. DFT calculation results show that when N and S are co-doped, the spin density of adjacent carbon atoms can be changed, thereby increasing the CNS's binding energy to oxygen and conductivity. The excellent comprehensive performance of CNS undoubtedly discloses its potential practical application in the energy conversation and storage area.

The interaction between a luminescent covalent organic framework (COF) and the indoor pollutant NH3 was investigated based on density functional theory and time-dependent density functional theory. The frontier molecular orbitals and electronic configuration showed that the luminescence mechanism of the COF was strongly affected by the hydrogen bond between the COF and NH3. In addition, the calculated hydrogen bond length, infrared (IR) spectra, and proton nuclear magnetic resonance (1H NMR) spectroscopy analysis indicated that the hydrogen bond in the S1 state was enhanced, which is identical to the calculated results of electronic excitation energies. The fluorescence rate coefficient of the COF was reduced when interacting with NH3. The hydrogen bond between the COF and NH3 in the S1 state is critical for the COF luminescence properties, which means that the COF shows potential application in the detection of NH3.

Porous carbon materials have been regarded as attractive hosts for lithium sulfur batteries. However, the electron conductivity and Li+ ion diffusion need to be enhanced due to the low graphitization and the restricted ion transport. In order to improve the rate capability and cycling stability of the cathode, we propose a wafer-like structure to realize the high conductivity and structural stability of the porous carbon substrate. The graphene layers ensure high electron transport, while the sandwiched porous carbon with a micro/mesoporous structure guarantees fast ion diffusion. Meanwhile, the wafer-like structure enjoys good structural stability and also endows the cathode with a long cycle life. The obtained S/I-rGO-G cathode delivers a high specific capacity of 1138 mA h g−1 at 0.1C, a favorable capacity retention of 600 mA h g−1 after 200 cycles at 1C and a superior rate capability of 638 mA h g−1 at 2C.

Development of highly active and durable non-precious metal bi-functional electrocatalyst for both oxygen reduction and evolution reaction (ORR and OER) remains a significant challenge. Herein, porous mixed spinel MnCoxO4 was loaded on the N-doped multi-walled carbon nanotubes (MnCoxO4/NCNT) through a facile one-pot hydrothermal method to work as a bi-functional oxygen electrocatalyst. Physical characterizations confirm that the MnCoxO4 nanoparticles are composed of mixed spinel-type Co2MnO4 and (Co, Mn)[Mn, Co]2O4 with a diameter of 5–10 nm, which are dispersed on NCNT with secondary aggregation and resultant porous structure. Electrochemical measurements show that the MnCoxO4/NCNT catalyst exhibits high ORR catalytic activity with a dominant four-electron ORR catalytic pathway, remarkable durability, excellent methanol-tolerance, as well as superior OER catalytic activity with significantly decreased overpotential of 0.479 V in alkaline media. The multiple valence states of Co and Mn ions in MnCoxO4 coupled with the enlarged specific surface area with the help of NCNT exert crucial roles for the superior catalytic performance for both ORR and OER. Such a bi-functional oxygen electrocatalyst based on mixed spinel MnCoxO4 provides a new direction for developing low-cost, highly efficient, and robust multiple valence states transition metal-based electrocatalysts for oxygen electrode.

Controllable growth of uniform nanoparticles with specific morphology to obtain high active electrocatalyst is a key common problem in developing efficient energy conversion and storage devices. In this work, a tangerine peel-derived carbon (TPC) supported mixed manganese oxides (MnOx/TPC) was synthesized for oxygen reduction reaction (ORR) through a facile pyrolysis procedure. By making full use of the confinement effect of tangerine peel cells, the MnOx nanoparticles of MnOx/TPC-800 are obtained with a components of Mn(II), Mn(III) and Mn(IV) with cubic morphology of about 15 nm and evenly dispersed on the TPC surface. Electrochemistry measurements show that MnOx/TPC-800 demonstrates excellent ORR performance with a comparable half-wave potential to commercial Pt/C and a high onset potential with a dominant 4e− catalytic process, superior stability, and remarkable immunity to methanol crossover effect in alkaline media. The synergy effect between multi-oxidation states MnOx and TPC of MnOx/TPC-800 is proved to play significant factor for its high ORR performance. This study provides a valuable and rational strategy to construct morphology-controlled metal nanoparticles with unique carbon materials in developing cost-effective catalysts for fuel cells and metal air batteries.

The development of cost-effective and durable oxygen electrocatalysts remains highly critical but challenging for energy conversion and storage devices. Herein, a novel FeNi alloy nanoparticle core encapsulated in carbon shells supported on a N-enriched graphene-like carbon matrix (denoted as FeNi@C/NG) was constructed by facile pyrolyzing the mixture of metal salts, glucose, and dicyandiamide. The in situ pyrolysis of dicyandiamide in the presence of glucose plays a significant effect on the fabrication of the porous FeNi@C/NG with a high content of doped N and large specific surface area. The optimized FeNi@C/NG catalyst displays not only a superior catalytic performance for the oxygen reduction reaction (ORR, with an onset potential of 1.0 V and half-wave potential of 0.84 V) and oxygen evolution reaction (OER, the potential at 10 mA cm-2 is 1.66 V) simultaneously in alkaline, but also outstanding long-term cycling durability. The excellent bifunctional ORR/OER electrocatalytic performance is ascribed to the synergism of the carbon shell and FeNi alloy core together with the high-content of nitrogen doped on the large specific surface area graphene-like carbon.

Exploring cost-effective, high-performance and durable non-precious metal catalysts is of great significance for the acceleration of sluggish oxygen reduction reaction (ORR). Here, we report an intriguing heteroatom-doped graphitized carbon encased Fe species composite by introducing N, S and B sequentially. The experimental approach was designed ingeniously for that the FeCl3·6H2O could catalyze thiourea to synthesize N, S co-doped carbon materials which would further react with H3BO3 and NH3 (emerged at the heat-treatment process) to prepare N, S and B co-doped carbon materials (Fe-N/S/B-C). The Fe-N/S/B-C exhibits an impressive ORR activity for its half-wave potential of −0.1 V, which is 36 mV or 19 mV higher than that of the corresponding single or dual doped counterparts (Fe-N-C or Fe-N/S-C) and 31 mV positive than that of Pt/C catalyst, respectively. Further chronoamperometric measurement and accelerated aging test confirm the excellent electrochemical durability of Fe-N/S/B-C with the stable core–shell structure. The remarkable ORR performance and facile preparation method enable Fe-N/S/B-C as a potential candidate in electrochemical energy devices.

This article presents a recognition mechanism for nitro-explosives by the luminescent metal-organic framework 1 (LMOF-1) with the aid of density functional theory (DFT) and time-dependent density functional theory (TDDFT). The behavior of hydrogen bonding between the LMOF-1 and nitro-explosives in the S1 state is closely associated with the fluorescence properties of the LMOF-1. In our research, we calculated the geometric configuration, 1H NMR and IR spectra of the Complex 2 formed by LMOF-1 and nitrobenzene in the S0 and S1 states. The results showed that the hydrogen bond in the S1 state was increased, which was unfavorable for the luminescence of LMOF-1. Furthermore, the fluorescence rate of LMOF-1 decreased after encapsulating nitrobenzene into it. These calculated results collectively suggest that LMOF-1 is a potential fluorescence sensor for the detection of nitro-explosives. This research was aiming to provide a better understanding of the recognition mechanism by LMOFs for nitro-explosives.

The construction of nonprecious metal catalysts for the oxygen reduction reaction (ORR) is highly desirable but remains as a key challenge for fuel cells and metal–air batteries. Herein, we designed and synthesized novel Fe2P nanoparticles embedded in an N,P co-doped mesoporous carbon catalyst (Fe2P/NPC) through direct pyrolysis of o-methylaniline in the presence of FeCl3·6H2O, H3PO4, silica nanospheres, and hexadecyltrimethyl ammonium bromide (CTAB) micelles. Transmission electron microscopy, Brunauer–Emmett–Teller (BET), X-ray diffraction and X-ray photoelectron spectroscopy measurements demonstrated that the obtained three-dimensional mesoporous Fe2P/NPC catalyst possessed a considerable specific surface area of 785 m2 g−1 with high contents of Fe2P nanoparticles, pyridinic N, and graphitic N species. Electrochemical evaluations showed that the formed Fe2P/NPC exhibited superior ORR performance to Pt/C in terms of a comparable onset potential (−0.01 V vs. Ag/AgCl electrode), about 20 mV higher half-wave potential, excellent stability and remarkable methanol tolerance in alkaline media. The synergistic effect of pyridinic N, graphitic N and Fe2P species together with its three-dimensional porous structure contribute to the impressive ORR performance. This research, most importantly, provides new clues to the rational development of cost-effective FePx-based catalysts for the ORR.

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeCx nanoparticles and porous carbon composited catalyst (Fe/FeCx@NC) via a facile two-step heat treatment strategy. The Fe/FeCx@NC-800−0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeCx@NC-T−t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeCx@NC-800−0.5 is caused by the synergistic effect between Fe/FeCx core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.

Phenol is considered as one of the most important pollutants in the water environment, and thus its detection plays a cardinal role in environmental assessment and treatment. In this study, high quality carbon quantum dots (CQDs) were successfully prepared by ozone oxidation, with cheap coal as the carbon material. The as-prepared CQDs exhibited a narrow size distribution between 2 and 9 nm, with an average size of approximately 4.2 nm. The novel CQDs showed high sensitivity and selectivity for phenol detection with a low detection limit of 0.076 μM in water due to the fluorescence quenching effect of the CQDs, which is attributed to the hydrogen bonds (CO⋯H–O) between phenol and the fluorescent CQDs according to the density functional theory (DFT) and time-dependent density functional theory (TDDFT) results. The theoretical calculation matches well with the experimental data, which provides us a new way to investigate the detection mechanism of the CQDs for phenol.

Exploring low-cost and high-performance nonprecious metal catalysts for oxygen reduction reaction (ORR) in fuel cells is crucial for the commercialization of energy conversion and storage devices. Here we report a three-dimensional hierarchical porous Fe, N doped carbon catalysts synthesized by a facile pyrolysis method using silica nanospheres as template, glucose, FeSO 4 ·7H 2 O and dicyandiamide as the carbon, iron and nitrogen precursors, respectively. The corresponding 3DHP/Fe-N-C-900 catalyst exhibits superior ORR activity with the onset potential of 0 V ( vs . Ag/AgCl) and long-term stability than that of 20 wt. % Pt/C in alkaline medium. The excellent ORR performance of 3DHP/Fe-N-C-900 can be attributed to the synergistic effect of Fe 3 O 4 and doped N, as well as the three-dimensional meso/macroporous structure with high surface area. The finding of high ORR activity of Fe 3 O 4 nanoparticles coupling with hierarchical porous N-doped carbon materials opens a new avenue for the construction of cost-effective Fe-N-C catalysts for fuel cells.

Rational design and construction of robust electrocatalysts towards oxygen reduction reaction (ORR) are vital for energy conversion devices. Here, we report a hierarchically engineered Co nanoparticle (NP) encapsulated in Co, N codoped graphene-like carbon sample (Co@NC) via direct pyrolyzing the mixture of glucose, dicyandiamide and cobalt salt. Benefiting from the Co-N4 moiety and high content of doped N species (8.81 at.%) which highly dispersed on the large Co NP modified carbon surface, Co@NC sample delivers remarkable ORR catalytic performance with an onset potential of 0.98 V and a half-wave potential of 0.86 V together with robust durability, which outperforms the benchmark Pt/C catalyst and most of published Co-Nx-C samples in alkali. This facile mass-producible strategy undoubtedly provides an avenue to achieve highly active and durable practical-oriented electrocatalytic catalysts for wide electrochemical energy devices.

Development of efficient, low-cost and good stability electrocatalysts as alternatives to platinum for the oxygen reduction reaction (ORR) is of significance for fuel cells. Here we report a novel type of Fe, N supported carbon nanotube encapsulated with nitrogen doped graphene as an ORR electrocatalyst synthesized by a hydrothermal method, for which nitrogen-enriched melamine, ferric chloride and disodium edentate were used as the nitrogen, iron and graphene precursors, respectively. Disodium edentate plays an important role in the performance towards the ORR because it is not only a graphene precursor, but also the key of forming FeNx active sites. The prepared Fe-N-CNT@GN catalyst exhibits high ORR activity in alkaline media with an onset potential of −0.13 V, a limiting current density of 6.2 mA cm−2, and higher selectivity (number of electron transfer n ∼ 3.8) which might be due to the FeNx active sites. Moreover, the half-wave potential exhibits almost no changes after 8000 continuous cycles scanning from −0.3 V to 0.1 V. The tolerance to the methanol crossover effect in alkaline media is superior. The Fe-N-CNT@GN catalyst obtained by this method solves the problem of agglomeration, migration, dissolution and leaching of catalysts in alkaline media. This type of catalyst has great potential for use as a high-performance nonprecious metal cathode catalyst in PEMFCs.

The sluggish kinetics of oxygen reduction reaction and oxygen evolution reaction (ORR/OER) are the key scientific issues that need to be addressed for the application of renewable energy technologies. Rational coupling transition metal with porous heteroatom-doped carbon is extensively investigated as an efficient strategy to achieve high performance ORR/OER nonprecious metal electocatalysts. In this study, a FeNi alloy coated with N-doped carbon material (namely FeNi/NC) was designed by using triblock copolymer Pluronic F127 as a surfactant co-assembly with g-C3N4. This strategy enabled FeNi/NC possessing a high BET surface area in terms of three-dimensional hierarchical porous structure together with abundant defect sites. The optimized FeNi/NC catalyst displays an excellent oxygen electrode electrocatalytic activity with a potential gap △E of 0.77 V in alkaline media which substantially outperformed benchmark Pt/C + RuO2 (△E = 0.80 V). Furthermore, it shows almost no decay after long-time cycling tests for ORR/OER. The excellent catalytic performance along with the low cost for FeNi/NC catalyst makes it possible to commercialize the renewable energy devices.

Formaldehyde is the main cause of indoor pollution. In this research, we investigated the mechanism that the covalent organic framework (COF) identifies formaldehyde applying density functional theory (DFT) and time-dependent (TD) DFT approaches. On one hand, the calculation results of the geometric parameters, IR spectra, as well as 1H-NMR chemical shifts for protons that associated with the hydrogen bonding formation together with the electronic transition energies verified that the furcate hydrogen bonding formed between the COF and formaldehyde is enhanced in the excited S1 state and it is not beneficial to luminescence of the COF. On the other hand, excitingly, our further calculation results of the fluorescence rate coefficients also revealed that the strengthened hydrogen bonding behavior in S1 state caused an efficiently weakened luminescent phenomenon compared with that of the COF. Therefore, this analysis method, which qualitative collaborates with quantitative theoretically, demonstrates the possibility that the COF could be served as a sensor to detect formaldehyde. Graphical Abstract The luminescence of the Covalent Organic Framework can be greatly weakened after the addition of formaldehyde.

The preparation of three-dimensional ordered porous carbon materials (3DOPC) using colloidal crystal template (CCT) method is simple, economical and reproducible. Colloidal crystals play a supporting role in skeleton and can flexibly regulate the structure of the materials by modifying the structure of CCT which is a highly controllable hard-template. The 3DOPC has a large specific surface area, high porosity, and low bending spherical pores, which makes it widely applied in the field of adsorption, catalysis, energy reserves and other areas. This article reviews the recent synthesis of 3DOPC materials by CCT method and its application in electrochemistry, focusing on the different colloidal crystal template methods to prepare 3DOPC, the application in electrochemistry and the prospects of its research.

Promoting the oxygen reduction reaction (ORR) catalytic activities of cost-effective catalysts is of great significance for the development of various energy conversion and storage systems. Herein, we describe the preparation of a highly active N- and S-co-doped ketjenblack (Kb) by facile pyrolysis of a mixture of thiourea and Kb in the presence of FeCl3⋅6 H2O followed by an acid-leaching process. This novel synthetic approach was rationally designed with the consideration that thiourea could easily introduce both N and S heteroatoms into the carbon matrix by a heat-treatment method by releasing plentiful reactive N- and S-containing gases, which could simultaneously optimize the porous structure of the resultant catalyst. Physical characterization revealed that N and S were homogeneously incorporated into the nanostructure of Kb and formed a hierarchical porous structure with a high specific surface area. The N/S-Kb catalyst showed impressive ORR activity, with an onset potential of 0.08 V at 0.1 mA cm−2, which is 20 mV more positive than that of commercial 20 wt. % Pt/C catalyst. This was coupled with long-term durability and superior methanol tolerance in alkaline media. The improved ORR performance can be mainly ascribed to synergistic contributions of highly efficient active sites arising from high contents of thiophene S and pyridinic N along with the high specific surface area and the favorable mass-transport properties arising from the hierarchical porous structure. The remarkable ORR performance and facile preparation method make the N/S-Kb catalyst a promising substitute for Pt in electrochemical energy devices.

A ferrocene-based ionic liquid (Fe-IL) is used as a metal-containing feedstock with a nitrogen-enriched ionic liquid (N-IL) as a compatible nitrogen content modulator to prepare a novel type of non-precious-metal–nitrogen–carbon (M-N-C) catalysts, which feature ordered mesoporous structure consisting of uniform iron oxide nanoparticles embedded into N-enriched carbons. The catalyst Fe 10 @NOMC exhibits comparable catalytic activity but superior long-term stability to 20 wt% Pt/C for ORR with four-electron transfer pathway under alkaline conditions. Such outstanding catalytic performance is ascribed to the populated Fe (Fe 3 O 4 ) and N (N2) active sites with synergetic chemical coupling as well as the ordered mesoporous structure and high surface area endowed by both the versatile precursors and the synthetic strategy, which also open new avenues for the development of M-N-C catalytic materials.