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Journal ArticleDOI: 10.1039/D0TA08741F

Selective nitrogen reduction to ammonia on iron porphyrin-based single-site metal–organic frameworks

02 Mar 2021-Journal of Materials Chemistry (Royal Society of Chemistry (RSC))-Vol. 9, Iss: 8, pp 4673-4678
Abstract: Constructing efficient catalysts for N2 reduction into value added ammonia under ambient conditions is a considerable challenge. Herein, well-defined single-site metal–organic frameworks (MOFs, M–TCPP; M = Fe, Co, or Zn) were constructed and evaluated as electrocatalysts for N2 reduction. The prepared Fe–TCPP exhibited prominent performance with a high NH3 yield of 44.77 μg h−1 mgcat.−1 and a faradaic efficiency of 16.23%, superior to that of all the reported molecular and MOF catalysts. The superior performance was ascribed to the highly effective N2 activation at the Fe site, and benefited from the overall reaction thermodynamics advantage in the key reaction step of *NNH formation. This study gives an understanding of the intrinsic activity of well-defined catalysts in the electrocatalytic N2 reduction, and provides atomic-level insights into the rational design and engineering of highly active catalysts for artificial N2 fixation.

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Topics: Catalysis (51%), Metal-organic framework (50%)

7 results found

Open accessJournal Article
Abstract: Electrochemical N₂ reduction has emerged as a sustainable and eco-friendly route for the artificial synthesis of NH₃ under ambient conditions, but active electrocatalysts are needed to drive the N₂ reduction reaction (NRR). Here, Bi nanodendrites are reported as an efficient NRR electrocatalyst for N₂ to NH₃ conversion with excellent selectivity. In 0.1 M HCl, this catalyst achieves a large NH₃ yield of 25.86 μg h⁻¹ mg⁻¹cₐₜ. and a high faradaic efficiency of 10.8% at −0.60 V and −0.55 V versus a reversible hydrogen electrode, respectively, with high electrochemical durability.

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26 Citations

Open accessJournal ArticleDOI: 10.1186/S40580-021-00273-8
Seokwoo Choe1, Sung Min Kim1, Yeji Lee1, Jin Seok1  +3 moreInstitutions (2)
02 Aug 2021-Nano Convergence
Abstract: Photocatalytic N2 reduction has emerged as one of the most attractive routes to produce NH3 as a useful commodity for chemicals used in industries and as a carbon-free energy source. Recently, significant progress has been made in understanding, exploring, and designing efficient photocatalyst. In this review, we outline the important mechanistic and experimental procedures for photocatalytic NH3 production. In addition, we review effective strategies on development of photocatalysts. Finally, our analyses on the characteristics and modifications of photocatalysts have been summarized, based on which we discuss the possible future research directions, particularly on preparing more efficient catalysts. Overall, this review provides insights on improving photocatalytic NH3 production and designing solar-driven chemical conversions.

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Topics: Energy source (53%)

Open accessJournal ArticleDOI: 10.1021/JACS.1C11158
Haixia Zhong, Mingchao Wang, Mahdi Ghorbani-Asl1, Jichao Zhang2  +11 moreInstitutions (7)
Abstract: The electrochemical N2 reduction reaction (NRR) under ambient conditions is attractive in replacing the current Haber-Bosch process toward sustainable ammonia production. Metal-heteroatom-doped carbon-rich materials have emerged as the most promising NRR electrocatalysts. However, simultaneously boosting their NRR activity and selectivity remains a grand challenge, while the principle for precisely tailoring the active sites has been elusive. Herein, we report the first case of crystalline two-dimensional conjugated covalent organic frameworks (2D c-COFs) incorporated with M-N4-C centers as novel, defined, and effective catalysts, achieving simultaneously enhanced activity and selectivity of electrocatalytic NRR to ammonia. Such 2D c-COFs are synthesized based on metal-phthalocyanine (M = Fe, Co, Ni, Mn, Zn, and Cu) and pyrene units bonded by pyrazine linkages. Significantly, the 2D c-COFs with Fe-N4-C center exhibit higher ammonia yield rate (33.6 μg h-1 mgcat-1) and Faradaic efficiency (FE, 31.9%) at -0.1 V vs reversible hydrogen electrode than those with other M-N4-C centers, making them among the best NRR electrocatalysts (yield rate >30 μg h-1 mgcat-1 and FE > 30%). In situ X-ray absorption spectroscopy, Raman spectroelectrochemistry, and theoretical calculations unveil that Fe-N4-C centers act as catalytic sites. They show a unique electronic structure with localized electronic states at Fermi level, allowing for stronger interaction with N2 and thus faster N2 activation and NRR kinetics than other M-N4-C centers. Our work opens the possibility of developing metal-nitrogen-doped carbon-rich 2D c-COFs as superior NRR electrocatalyst and provides an atomic understanding of the NRR process on M-Nx-C based electrocatalysts for designing high-performance NRR catalysts.

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Topics: Electrocatalyst (52%), Ammonia production (51%)


49 results found

Journal ArticleDOI: 10.1038/NENERGY.2016.184
Shenlong Zhao1, Shenlong Zhao2, Yun Wang3, Juncai Dong4  +20 moreInstitutions (5)
28 Nov 2016-Nature Energy
Abstract: The design and synthesis of efficient electrocatalysts are important for electrochemical conversion technologies. The oxygen evolution reaction (OER) is a key process in such conversions, having applications in water splitting and metal–air batteries. Here, we report ultrathin metal–organic frameworks (MOFs) as promising electrocatalysts for the OER in alkaline conditions. Our as-prepared ultrathin NiCo bimetal–organic framework nanosheets on glassy-carbon electrodes require an overpotential of 250 mV to achieve a current density of 10 mA cm−2. When the MOF nanosheets are loaded on copper foam, this decreases to 189 mV. We propose that the surface atoms in the ultrathin MOF sheets are coordinatively unsaturated—that is, they have open sites for adsorption—as evidenced by a suite of measurements, including X-ray spectroscopy and density-functional theory calculations. The findings suggest that the coordinatively unsaturated metal atoms are the dominating active centres and the coupling effect between Ni and Co metals is crucial for tuning the electrocatalytic activity. Efficient electrocatalysts for the oxygen–evolution reaction are desired due to their importance in applications such as water splitting and metal–air batteries. Here, the authors engineer ultrathin metal–organic frameworks that require low overpotential to generate oxygen from alkaline media.

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Topics: Overpotential (55%), Water splitting (52%), Oxygen evolution (51%)

1,324 Citations

Journal ArticleDOI: 10.1002/ADMA.201503648
Meiting Zhao1, Yixian Wang2, Yixian Wang1, Qinglang Ma1  +10 moreInstitutions (2)
01 Dec 2015-Advanced Materials
Abstract: A facile surfactant-assisted bottom-up synthetic method to prepare a series of freestanding ultrathin 2D M-TCPP (M = Zn, Cu, Cd or Co, TCPP = tetrakis(4-carboxyphenyl)porphyrin) nanosheets with a thickness of sub-10 nm is developed. As a proof-of-concept application, some of them are successfully used as new platforms for DNA detection. The Cu-TCPP nanosheet-based sensor shows excellent fluorescent sensing performance and is used for the simultaneous detection of multiple DNA targets.

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Topics: Nanosheet (54%)

586 Citations

Journal ArticleDOI: 10.1002/ADMA.201604437
Xue Feng Lu1, Lin-Fei Gu1, Jia-Wei Wang1, Jun-Xi Wu1  +2 moreInstitutions (1)
01 Jan 2017-Advanced Materials
Abstract: Porous CoFe2 O4 /C NRAs supported on nickel foam@NC (denoted as NF@NC-CoFe2 O4 /C NRAs) are directly fabricated by the carbonization of bimetal-organic framework NRAs grown on NF@poly-aniline(PANI), and they exhibit high electrocatalytic activity, low overpotential, and high stability for the oxygen evolution reaction in alkaline media.

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Topics: Overpotential (56%), Nanorod (53%), Oxygen evolution (53%) ... show more

548 Citations

Journal ArticleDOI: 10.1002/AENM.201800369
Xiaoyang Cui1, Cheng Tang1, Qiang Zhang1Institutions (1)
Abstract: DOI: 10.1002/aenm.201800369 reactions involved.[1] In recent years, tremendous progress has been achieved in the field of heterogeneous electrocatalysis, with rapid development of multifarious electocatalysts toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR). However, electrocatalysts for the reduction of dinitrogen (N2) to ammonia (NH3) at room temperature and atmospheric pressure remain largely underexplored, despite the fact that investigations on catalysts and reaction systems for artificial nitrogen fixation have been continued for more than 100 years.[2–4] Ammonia is primarily used for producing fertilizers to sustain the world’s population.[5] It also serves as a green energy carrier and a potential transportation fuel.[6] Currently, ammonia synthesis is dominated by the industrial Haber–Bosch process using heterogeneous iron-based catalysts at high temperature (300–500 °C) and high pressure (150–300 atm),[7] accounting for more than 1% of the world’s energy supply and generating more than 300 million metric tons of fossil fuel–derived CO2 annually.[8,9] Hence, it is desirable to develop alternative processes that have the potential to overcome the limitations of the Haber–Bosch process including harsh conditions, complex plant infrastructure, centralized distribution, high energy consumption, and negative environmental impacts. In nature, biological N2 fixation occurs under mild conditions via nitrogenase enzymes that contain FeMo, FeV, or FeFe cofactor as catalytic active sites.[10,11] Developed man-made catalysts are therefore stimulated to reduce N2 upon the addition of protons and electrons, which is similar to the nitrogenase catalytic process. Transition metal–dinitrogen complexes such as the molybdenum–, iron–, and cobalt–dinitrogen complexes have been proposed as homogeneous catalysts for the reduction of N2 into NH3 under ambient conditions;[12] however, the stability and recycling issues are challenging.[13] On the other hand, electrochemical and photochemical reduction processes using heterogeneous catalysts benefit from clean and renewable energy sources and are promising for achieving NH3 production directly from N2 and water.[14] The electrochemical reduction of N2 to NH3 can be more efficient than the photochemical counterpart. This is because not all of the photons in the photochemical reduction process can The production of ammonia (NH3) from molecular dinitrogen (N2) under mild conditions is one of the most attractive topics in the field of chemistry. Electrochemical reduction of N2 is promising for achieving clean and sustainable NH3 production with lower energy consumption using renewable energy sources. To date, emerging electrocatalysts for the electrochemical reduction of N2 to NH3 at room temperature and atmospheric pressure remain largely underexplored. The major challenge is to achieve both high catalytic activity and high selectivity. Here, the recent progress on the electrochemical nitrogen reduction reaction (NRR) at ambient temperature and pressure from both theoretical and experimental aspects is summarized, aiming at extracting instructive perceptions for future NRR research activities. The prevailing theories and mechanisms for NRR as well as computational screening of promising materials are presented. State-of-the-art heterogeneous electrocatalysts as well as rational design of the whole electrochemical systems for NRR are involved. Importantly, promising strategies to enhance the activity, selectivity, efficiency, and stability of electrocatalysts toward NRR are proposed. Moreover, ammonia determination methods are compared and problems relating to possible ammonia contamination of the system are mentioned so as to shed fresh light on possible standard protocols for NRR measurements.

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524 Citations

Journal ArticleDOI: 10.1002/ADMA.201803498
Zhigang Geng1, Yan Liu1, Xiangdong Kong1, Pai Li1  +6 moreInstitutions (2)
01 Oct 2018-Advanced Materials
Abstract: The electrochemical reduction of N2 into NH3 production under ambient conditions represents an attractive prospect for the fixation of N2 . However, this process suffers from low yield rate of NH3 over reported electrocatalysts. In this work, a record-high activity for N2 electrochemical reduction over Ru single atoms distributed on nitrogen-doped carbon (Ru SAs/N-C) is reported. At -0.2 V versus reversible hydrogen electrode, Ru SAs/N-C achieves a Faradaic efficiency of 29.6% for NH3 production with partial current density of -0.13 mA cm-2 . Notably, the yield rate of Ru SAs/N-C reaches 120.9 μgNH3 mgcat.-1 h-1, which is one order of magnitude higher than the highest value ever reported. This work not only develops a superior electrocatalyst for NH3 production, but also provides a guideline for the rational design of highly active and robust single-atom catalysts.

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477 Citations