The electrochemical nitrogen reduction reaction (NRR) is a very efficient method for sustainable NH3 production, but it requires effective catalysts to expedite the NRR kinetics and inhibit the ...concomitant hydrogen evolution reaction (HER). Two-dimensional (2D)/2D interface engineering is an effective method to design powerful catalysts due to intimate face-to-face contact of two 2D materials that facilitates the strong interfacial electronic interactions. Herein, we explored a 2D/2D MoS2/C3N4 heterostructure as an active and stable NRR catalyst. MoS2/C3N4 exhibited a conspicuously improved NRR performance with an NH3 yield of 18.5 μg h–1 mg–1 and a high Faradaic efficiency (FE) of 17.8% at −0.3 V, far better than those of the individual MoS2 or C3N4 component. Density functional theory calculations revealed that the interfacial charge transport from C3N4 to MoS2 could enhance the NRR activity of MoS2/C3N4 by promoting the stabilization of the key intermediate *N2H on Mo edge sites of MoS2 and concurrently decreasing the reaction energy barrier. Meanwhile, MoS2/C3N4 rendered a more favorable *H adsorption free energy on S edge sites than on Mo edge sites of MoS2, thereby protecting the NRR-active Mo edge sites from the competing HER and leading to a high FE.
Electrochemical reduction of N2 to NH3 is a promising method for artificial N2 fixation, but it requires efficient and robust electrocatalysts to boost the N2 reduction reaction (NRR). Herein, a ...combination of experimental measurements and theoretical calculations revealed that a hybrid material in which ZnO quantum dots (QDs) are supported on reduced graphene oxide (ZnO/RGO) is a highly active and stable catalyst for NRR under ambient conditions. Experimentally, ZnO/RGO was confirmed to favor N2 adsorption due to the largely exposed active sites of ultrafine ZnO QDs. DFT calculations disclosed that the electronic coupling of ZnO with RGO resulted in a considerably reduced activation‐energy barrier for stabilization of *N2H, which is the rate‐limiting step of the NRR. Consequently, ZnO/RGO delivered an NH3 yield of 17.7 μg h−1 mg−1 and a Faradaic efficiency of 6.4 % in 0.1 m Na2SO4 at −0.65 V (vs. RHE), which compare favorably to those of most of the reported NRR catalysts and thus demonstrate the feasibility of ZnO/RGO for electrocatalytic N2 fixation.
ZnO/RGO can fix it: A hybrid material, in which ZnO quantum dots are supported on reduced graphene oxide (ZnO/RGO), was synthesized by a facile, one‐step, microwave‐assisted solvothermal method and found to be a highly active and stable catalyst for the electrochemical reduction of dinitrogen to ammonia (see figure) under ambient conditions, which is a promising method for artificial nitrogen fixation.
The strong interface is an essential requirement to ensure the effective load transfer of graphene/Cu composites. Here we attempted to improve the interface adhesion and mechanical properties of ...reduced graphene oxide (RGO)/CuCr composites by matrix-alloying with ∼0.2 at.% Cr. It was found that a trace amount of Cr7C3 layers/nanoparticles was in-situ formed at the RGO-CuCr interface, which contributed to the dramatically improved interfacial bonding of the composites. The 2.5 vol% RGO/CuCr composite exhibited a tensile strength of 352 MPa, 82% and 19% higher than that of unreinforced CuCr and 2.5 vol% RGO/Cu composite without Cr alloying, respectively. The enhanced strength of RGO/CuCr composite was ascribed to the dual role of Cr7C3 layers/nanoparticles that not only enhanced the load transfer efficiency, but also promoted the dislocation strengthening ability of RGO itself. Furthermore, we proposed the possible Cr7C3 formation/evolution mechanism that involved the four steps of amorphous carbon formation, Cr7C3 nucleation in amorphous carbon, Cr7C3 growth and Cr7C3 coalescence. The formation of medium sized Cr7C3 layers/nanoparticles at 1053 K resulted in the highest strength of RGO/CuCr composite with a satisfactory strength-ductility combination. This study provides new insights into the interface structure, strengthening mechanism and carbide formation/evolution mechanism of graphene/CuX composites.
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Electrocatalytic N2 reduction reaction (NRR) provides an effective and renewable approach for artificial NH3 production, but still remains a grand challenge because of the low NH3 yield and Faradaic ...efficiency (FE). Herein, we reported that the SnO2 quantum dots (QDs) supported on reduced graphene oxide (RGO) could efficiently and stably catalyze NRR at ambient conditions. The NRR performance of resulting SnO2/RGO was studied by both experimental techniques and density functional theory calculations. It was found that the ultrasmall SnO2 QDs (2 nm) grown on RGO could provide abundant sites for efficient N2 adsorption. Significantly, the strongly electronically coupled SnO2 QDs and RGO brought about the enhanced conductivity and the decreased work function, which led to a considerably lowered energy barrier of *N2 → *N2H that was the rate-determining step of the NRR process. Meanwhile, the SnO2/RGO exhibited inferior hydrogen evolution reaction activity. As a result, the SnO2/RGO delivered a high NH3 yield of 25.6 μg h–1 mg–1 (5.1 μg cm–2h–1) and an FE of 7.1% in 0.1 M Na2SO4 at −0.5 V (vs RHE), together with the outstanding selectivity and stability, endowing it as a promising electrocatalyst for N2 fixation.
The development of highly active and durable electrocatalysts toward the N2 reduction reaction (NRR) holds a key to ambient electrocatalytic NH3 synthesis. Herein, fluorine (F)-doped SnO2 mesoporous ...nanosheets on carbon cloth (F-SnO2/CC) were developed as an efficient NRR electrocatalyst. Benefiting from the combined structural advantages of mesoporous nanosheet structure and F-doping, the F-SnO2/CC exhibited high NRR activity with an NH3 yield of 19.3 μg h–1 mg–1 and a Faradaic efficiency of 8.6% at −0.45 V (vs RHE) in 0.1 M Na2SO4, comparable or even superior to those of most reported NRR electrocatalysts. Density functional theory calculations revealed that the F-doping could readily tailor the electronic structure of SnO2 to render it with improved conductivity and increased positive charge on active Sn sites, leading to the lowered reaction energy barriers and boosted NRR activity.
Electrocatalytic N2 reduction reaction (NRR) provides a sustainable approach for ambient N2 fixation. Non‐noble transition metal‐based electrocatalysts (TMEs) are emerging as the most promising NRR ...catalysts, but commonly exhibited limited NRR activity. Heteroatom doping is an effective method to improve the electrocatalytic activity of TMEs by finely modulating the electronic structures. Herein, as a proof‐of‐concept, nitrogen‐doped NiO nanosheet array on carbon cloth (N‐NiO/CC) was investigated as model heteroatom‐doped TMEs for NRR. The N‐NiO/CC exhibited the considerably enhanced NRR performance with a NH3 yield of 22.7 μg h−1 mg−1 and an FE of 7.3 % in 0.1 M LiClO4 at −0.5 V (vs. RHE), far superior to those of undoped counterpart. Density functional theory (DFT) calculations revealed that the N‐doping could induce the enhanced surface conductivity and upraised d‐band center, leading to promoted *NNH stabilization, reduced reaction energy barrier and thus improved NRR performance.
It's dope! A nitrogen‐doped NiO nanosheet array on carbon cloth (N‐NiO/CC) exhibited enhanced NRR performance with a NH3 yield of 22.7 μg h−1 mg−1 and an FE of 7.3 % in 0.1 M LiClO4 at −0.5 V (vs. RHE), far superior to those of undoped counterparts (NiO/CC). DFT calculations revealed that the N‐doping could induce enhanced surface conductivity and an upraised d‐band center, leading to promoted *NNH stabilization, a reduced reaction energy barrier, and thus improved NRR performance.
Mo2C nanoparticles grown on reduced graphene oxide (Mo2C@RGO) were used to prepare the Mo2C@RGO/Cu composite. The Mo2C nanoparticles played a bridging role in not only being firmly attached on RGO ...but also forming a semi-coherent interface with the Cu matrix, leading to strong interfacial bonding of the composites. The 1 vol% Mo2C@RGO/Cu composite exhibited a yield strength of 238 MPa, 58% and 127% higher than that of 1 vol% RGO/Cu composite and pure Cu, respectively. The strengthening mechanism of Mo2C@RGO/Cu composite relied on the dual role of Mo2C nanoparticles that not only enhanced the load transfer strengthening of RGO but also provided the possible Orowan strengthening themselves. Nevertheless, the Mo2C@RGO/Cu composite showed a drop in coefficient of thermal expansion but a reduced thermal conductivity compared to pure Cu and the RGO/Cu composite. This study provides new insights into the interface structure, strengthening mechanism and thermal behavior of carbide-modified graphene/metal composites.
The tunicamycins constitute a delicate mimic of the bisubstrate intermediates of N‐acetyl‐D‐hexosamine‐1‐phosphate translocases and thus inhibit bacterial cell‐wall synthesis and the N glycosylation ...of eukaryotic proteins. An efficient approach to the synthesis of this unique type of nucleoside antibiotics is now reported and features the assembly of five modules in a highly stereoselective and robust manner. A Mukaiyama aldol reaction, intramolecular acetal formation, gold(I)‐catalyzed O and N glycosylation, and final N acylation were used as the key steps.
The modular and stereoselective synthesis of tunicamycins features a Mukaiyama aldol reaction, intramolecular acetal formation, gold(I)‐catalyzed O and N glycosylation, and final N acylation as the key steps. These natural products are a unique type of nucleoside antibiotics with potent inhibitory activities against bacterial cell‐wall synthesis and the N‐glycosylation of eukaryotic proteins.
The total syntheses of 33 complex natural O-glycosides, such as the glycosides of macrocyclic lactones/lactams, enediynes, angucyclines, and anthracyclines, are highlighted, with a major focus being ...placed on the O-glycosylation reactions which connect the saccharides and the aglycones. These successful O-glycosylation reactions employ such donors as glycosyl bromides, fluorides, iodides, trichloroacetimidates, N-phenyl trifluoroacetimidates, thioglycosides, sulfoxides, heteroaryl thioglycosides, 1-hydroxyl sugars, 1-O-acetates, and ortho-alkynylbenzoates. Each synthesis is depicted starting from the O-glycosylation of the aglycone (or its precursor); the glycosylation conditions and outcomes (yields and stereoselectivities) are discussed, and the subsequent transformations toward the final target, including the elongation of the glycan, the elaboration of the aglycone, and the protecting group manipulations are also given in detail.
Subnanometric materials (SNMs) refer to nanomaterials with sizes comparable to the diameter of common linear polymers or confined at the level of a single unit cell in at least one dimension, usually ...<1 nm. Conventional inorganic nanoparticles are usually deemed to be rigid, lacking self-adjustable conformation. In contrast, the size at subnanometric scale endows SNMs with flexibility analogous to polymers, resulting in their abundant self-adjustable conformation. It is noteworthy that some highly flexible SNMs can adjust their shape automatically to form chiral conformation, which is rare in conventional inorganic nanoparticles. Herein, we summarize the chiral conformation of SNMs and clarify the driving force behind their formation, in an attempt to establish a better understanding for the origin of flexibility and chirality at subnanometric scale. In addition, the general strategies for controlling the conformation of SNMs are elaborated, which might shed light on the efficient fabrications of chiral inorganic materials. Finally, the challenges facing this area as well as some unexplored topics are discussed.
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