Abstract The current industrial ammonia synthesis relies on Haber–Bosch process that is initiated by the dissociative mechanism, in which the adsorbed N 2 dissociates directly, and thus is limited by ...Brønsted–Evans–Polanyi (BEP) relation. Here we propose a new strategy that an anchored Fe 3 cluster on the θ-Al 2 O 3 (010) surface as a heterogeneous catalyst for ammonia synthesis from first-principles theoretical study and microkinetic analysis. We have studied the whole catalytic mechanism for conversion of N 2 to NH 3 on Fe 3 /θ-Al 2 O 3 (010), and find that an associative mechanism, in which the adsorbed N 2 is first hydrogenated to NNH, dominates over the dissociative mechanism, which we attribute to the large spin polarization, low oxidation state of iron, and multi-step redox capability of Fe 3 cluster. The associative mechanism liberates the turnover frequency (TOF) for ammonia production from the limitation due to the BEP relation, and the calculated TOF on Fe 3 /θ-Al 2 O 3 (010) is comparable to Ru B5 site.
Although the maximized dispersion of metal atoms has been realized in the single‐atom catalysts, further improving the intrinsic activity of the catalysts is of vital importance. Here, the decoration ...of isolated Ru atoms into an edge‐rich carbon matrix is reported for the electrocatalytic hydrogen evolution reaction. The developed catalyst displays high catalytic performance with low overpotentials of 63 and 102 mV for achieving the current densities of 10 and 50 mA cm−2, respectively. Its mass activity is about 9.6 times higher than that of the commercial Pt/C‐20% catalyst at an overpotential of 100 mV. Experimental results and density functional theory calculations suggest that the edges in the carbon matrix enhance the local electric field at the Ru site and accelerate the reaction kinetics for the hydrogen evolution. The present work may provide insights into electrocatalytic behavior and guide the design of advanced electrocatalysts.
Isolated Ru atoms are decorated on an edge‐rich carbon matrix and applied as an efficient electrocatalyst for the hydrogen evolution reaction. This work demonstrates that the edges in a carbon matrix enable the integration of efficient charge delivery and a strong local electric field effect, which may shed light on the future design of efficient electrocatalysts.
Porous CoFe2O4/C NRAs supported on nickel foam@NC (denoted as NF@NC‐CoFe2O4/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.
Rational design and synthesis of highly active and robust bifunctional non‐noble electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required ...for efficient rechargeable metal–air batteries. Herein, abundant MnO/Co heterointerfaces are engineered in porous graphitic carbon (MnO/Co/PGC) polyhedrons via a facile hydrothermal‐calcination route with a bimetal–organic framework as the precursor. The in situ generated Co nanocrystals not only create well‐defined heterointerfaces with high conductivity to overcome the poor OER activity but also promote the formation of robust graphitic carbon. Owing to the desired composition and formation of the heterostructures, the resulting MnO/Co/PGC exhibits superior activity and stability toward both OER and ORR, which makes it an efficient air cathode for the rechargeable Zn–air battery. Importantly, the homemade Zn–air battery is able to deliver excellent performance including a peak power density of 172 mW cm−2 and a specific capacity of 872 mAh g−1, as well as excellent cycling stability (350 cycles), outperforming commercial mixed Pt/C||RuO2 catalysts. This work highlights the synergy from heterointerfaces in oxygen electrocatalysis, thus providing a promising approach for advanced metal–air cathode materials.
Interface engineering of MnO and Co in porous graphitic carbon (MnO/Co/PGC) polyhedrons is realized by a one‐step pyrolysis of bimetal–organic frameworks. Owing to the active heterointerfaces and robust graphitic carbon, the MnO/Co/PGC exhibits extraordinary activity and stability toward both OER and ORR, making it a promising air cathode for efficient metal–air batteries.
Designing novel non‐noble electrocatalysts with controlled structures and composition remains a great challenge for efficient hydrogen evolution reaction (HER). Herein, a rational synthesis of ...ultrafine carbide nanocrystals confined in porous nitrogen‐doped carbon dodecahedrons (PNCDs) by annealing functional zeolitic imidazolate framework (ZIF‐8) with molybdate or tungstate is reported. By controlling the substitution amount of MO4 units (M = Mo or W) in the ZIF‐8 framework, dual‐phase carbide nanocrystals confined in PNCDs (denoted as MC‐M2C/PNCDs) can be obtained, which exhibit superior activity toward the HER to the single‐phased MC/PNCDs and M2C/PNCDs. The evenly distributed ultrafine nanocrystals favor the exposure of active sites. PNCDs as the support facilitate charge transfer and protect the nanocrystals from aggregation during the HER process. Moreover, the strong coupling interactions between MC and M2C provide beneficial sites for both water dissociation and hydrogen desorption. This work highlights a new feasible strategy to explore efficient electrocatalysts via engineering on nanostructure and composition.
Dual‐phased carbide nanocrystals consisting of MC and M2C (M = Mo or W) are realized through controlling the amount of MO4 units substituted in a framework of ZIF‐8. Owing to the desired composition and ultrafine structures, the dual‐phased MC‐M2C/PNCDs exhibit better catalytic performances toward the hydrogen evolution reaction than single‐phased MC/PNCDs and M2C/PNCDs.
Developing noble‐metal‐free bifunctional oxygen electrocatalysts is of great significance for energy conversion and storage systems. Herein, we have developed a transformation method for growing ...NiMn‐based bimetal–organic framework (NiMn‐MOF) nanosheets on multi‐channel carbon fibers (MCCF) as a bifunctional oxygen electrocatalyst. Owing to the desired components and architecture, the MCCF/NiMn‐MOFs manifest comparable electrocatalytic performance towards oxygen reduction reaction (ORR) with the commercial Pt/C electrocatalyst and superior performance towards oxygen evolution reaction (OER) to the benchmark RuO2 electrocatalyst. X‐ray absorption fine structure (XAFS) spectroscopy and density functional theory (DFT) calculations reveal that the strong synergetic effect of adjacent Ni and Mn nodes within MCCF/NiMn‐MOFs effectively promotes the thermodynamic formation of key *O and *OOH intermediates over active NiO6 centers towards fast ORR and OER kinetics.
NiMn‐based bimetal–organic framework nanosheets are successfully grown on multi‐channel carbon fibers (MCCF/NiMn‐MOFs) as a promising bifunctional oxygen electrocatalyst. The strong synergetic effect of bimetallic nodes as well as the well‐designed hierarchical architecture is unraveled to enable MCCF/NiMn‐MOFs with fast kinetics and robust stability towards efficient oxygen electrocatalysis.
Electrochemical reduction of CO2 could mitigate environmental problems originating from CO2 emission. Although grain boundaries (GBs) have been tailored to tune binding energies of reaction ...intermediates and consequently accelerate the CO2 reduction reaction (CO2RR), it is challenging to exclusively clarify the correlation between GBs and enhanced reactivity in nanostructured materials with small dimension (<10 nm). Now, sub‐2 nm SnO2 quantum wires (QWs) composed of individual quantum dots (QDs) and numerous GBs on the surface were synthesized and examined for CO2RR toward HCOOH formation. In contrast to SnO2 nanoparticles (NPs) with a larger electrochemically active surface area (ECSA), the ultrathin SnO2 QWs with exposed GBs show enhanced current density (j), an improved Faradaic efficiency (FE) of over 80 % for HCOOH and ca. 90 % for C1 products as well as energy efficiency (EE) of over 50 % in a wide potential window; maximum values of FE (87.3 %) and EE (52.7 %) are achieved.
Ultrathin sub‐2 nm SnO2 quantum wires (QWs) composed of individual quantum dots with grain boundaries (GBs) being terminated on the surface were synthesized and examined for CO2 electrochemical reduction toward HCOOH formation. The ultrathin SnO2 QWs deliver higher current densities and remarkably higher Faraday efficiencies of HCOOH in a wide potential window as compared to SnO2 nanoparticles without exposed GBs.
Bi2O3 nanosheets were grown on a conductive multiple channel carbon matrix (MCCM) for CO2RR. The obtained electrocatalyst shows a desirable partial current density of ca. 17.7 mA cm−2 at a moderate ...overpotential, and it is highly selective towards HCOOH formation with Faradaic efficiency approaching 90 % in a wide potential window and its maximum value of 93.8 % at −1.256 V. It also exhibits a maximum energy efficiency of 55.3 % at an overpotential of 0.846 V and long‐term stability of 12 h with negligible degradation. The superior performance is attributed to the synergistic contribution of the interwoven MCCM and the hierarchical Bi2O3 nanosheets, where the MCCM provides an accelerated electron transfer, increased CO2 adsorption, and a high ratio of pyrrolic‐N and pyridinic‐N, while ultrathin Bi2O3 nanosheets offer abundant active sites, lowered contact resistance and work function as well as a shortened diffusion pathway for electrolyte.
Ultrathin Bi2O3 nanosheets have been successfully grown on a conductive multi‐channel carbon matrix (Bi2O3NSs@MCCM). The obtained Bi2O3NSs@MCCM electrocatalyst achieves a comparably high current density at a moderate overpotential for electrochemical CO2 reduction to HCOOH with high selectivity and good long‐term stability.
Confining nanostructured electrode materials in porous carbon represents an effective strategy for improving the electrochemical performance of lithium‐ion batteries. Herein, we report the design and ...synthesis of hybrid hollow nanostructures composed of highly dispersed Co3O4 hollow nanoparticles (sub‐20 nm) embedded in the mesoporous walls of carbon nanoboxes (denoted as H‐Co3O4@MCNBs) as an anode material for lithium‐ion batteries. The facile metal–organic framework (MOF)‐engaged strategy for the synthesis of H‐Co3O4@MCNBs involves chemical etching‐coordination and subsequent two‐step annealing treatments. Owing to the unique structural merits including more active interfacial sites, effectively alleviated volume variation, good and stable electrical contact, and easy access of Li+ ions, the H‐Co3O4@MCNBs exhibit excellent lithium‐storage performance in terms of high specific capacity, excellent rate capability, and cycling stability.
Hybrid hollow architectures composed of highly dispersed Co3O4 hollow nanoparticles embedded in the walls of mesoporous carbon nanoboxes (H‐Co3O4@MCNBs) are synthesized through an elaborate etching‐pyrolysis‐oxidation strategy starting from ZIF‐67 nanocubes. The H‐Co3O4@MCNBs obtained exhibit excellent lithium storage properties as an anode material.
Angiotensin‐I‐converting enzyme (ACE) inhibitory peptides are able to inhibit the activity of ACE, which is the key enzymatic factor mediating systemic hypertension. ACE‐inhibitory peptides can be ...obtained from edible proteins and have the function of antihypertension. The amino acid sequences and the secondary structures of ACE‐inhibitory peptides determine the inhibitory activities and stability. The resistance of ACE‐inhibitory peptides to digestive enzymes and peptidase affect their antihypertensive bioactivity in vivo. In this paper, the mechanism of ACE‐inhibition, sources of the inhibitory peptides, structure–activity relationships, stability during digestion, absorption and transportation of ACE‐inhibitory peptides, and consumption of ACE‐inhibitory peptides are reviewed, which provide guidance to the development of new functional foods and production of antihypertensive nutraceuticals and pharmaceuticals.
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