CO2 hydrogenation for the acquisition of value-added chemicals is an economical means to deal with the CO2-relevant environmental problems, among which CO2 reduction to CH4 is an excellent model ...reaction for investigating the initial steps of CO2 hydrogenation. For the supported catalysts commonly used in such reactions, the tailoring of the interfacial effect between metal centers and supporting materials so as to obtain superior low-temperature CO2 methanation performance is a significant but challenging subject. In this work, we altered the size regimes of the Ru deposits in Ru/CeO2 assemblies and uncovered the competitive relationship between the strong metal–support interactions (SMSI) and the H-spillover effect in determining the methanation activities by some ex situ and in situ spectroscopic techniques coupled with density functional theory (DFT) calculations. For CeO2 nanowire supported single Ru atoms, Ru nanoclusters (ca. 1.2 nm in size), and large Ru nanoparticles (ca. 4.0 nm in size), the nanoclusters show the most outstanding low-temperature CO2 methanation activity and 98–100% selectivity, with a turnover frequency (TOF) of 7.41 × 10–3 s–1 at 190 °C. The negative CO2 reaction order decreases their absolute values from single atoms to nanoclusters and turns positive in nanoparticles, while the positive H2 reaction order follows the reverse tendency. In situ DRIFTS measurements demonstrate that the dominant reaction pathway is the CO route, in which metal carbonyls are the critical intermediates and the active sites are those Ce3+–OH sites and Ru sites near the metal–support interfaces in charge of CO2 dissociation and carbonyl hydrogenation, respectively. Meanwhile, the strongest SMSI and H-spillover effect are respectively encountered in supported single Ru atoms and large Ru nanoparticles, with the activation of metal carbonyls and the dehydration of the support surfaces suppressed correspondingly. The two factors reach a balance in CeO2-supported Ru nanoclusters, and the methanation activity is therefore maximized. A mechanistic understanding of the interfacial effect in tuning the CO2 methanation activities would shed light on the ingenious design of the CO2 hydrogenation catalysts to utilize the SMSI and H-spillover effect to an appropriate degree and avoid their possible suppressions that would take place in extreme cases.
Synthesis of bimetallic nanomaterials with well controlled shape is an important topic in heterogeneous catalysis, low-temperature fuel cell technology, and many other fields. Compared with ...monometallic counterparts, bimetallic nanocatalysts endow scientists with more opportunities to optimize the catalytic performance by modulating the charge transfer between different metals, local coordination environment, lattice strain and surface element distribution. Considering the current challenges in shape controlled synthesis of bimetallic nanocatalysts, this tutorial review highlights some significant achievements in preparing bimetallic alloy, core-shell and heterostructure nanocrystals with well-defined morphologies, summarizes four general routes and some key factors of the bimetallic shape control scenarios, and provides some general ideas on how to design synthetic strategies to control the shape and exposing facets of bimetallic nanocrystals. The composition and shape dependent catalytic behaviours of bimetallic nanocrystals are reviewed as well.
Photocatalytic nitrogen fixation reaction can harvest the solar energy to convert the abundant but inert N2 into NH3. Here, utilizing metal–organic framework (MOF) membranes as the ideal assembly of ...nanoreactors to disperse and confine gold nanoparticles (AuNPs), we realize the direct plasmonic photocatalytic nitrogen fixation under ambient conditions. Upon visible irradiation, the hot electrons generated on the AuNPs can be directly injected into the N2 molecules adsorbed on Au surfaces. Such N2 molecules can be additionally activated by the strong but evanescently localized surface plasmon resonance field, resulting in a supralinear intensity dependence of the ammonia evolution rate with much higher apparent quantum efficiency and lower apparent activation energy under stronger irradiation. Moreover, the gas-permeable Au@MOF membranes, consisting of numerous interconnected nanoreactors, can ensure the dispersity and stability of AuNPs, further facilitate the mass transfer of N2 molecules and (hydrated) protons, and boost the plasmonic photocatalytic reactions at the designed gas–membrane–solution interface. As a result, an ammonia evolution rate of 18.9 mmol gAu –1 h–1 was achieved under visible light (>400 nm, 100 mW cm–2) with an apparent quantum efficiency of 1.54% at 520 nm.
Single‐atom catalysts (SACs) exhibit distinct catalytic behavior compared with nano‐catalysts because of their unique atomic coordination environment without the direct bonding between identical ...metal centers. How these single atom sites interact with each other and influence the catalytic performance remains unveiled as designing densely populated but stable SACs is still an enormous challenge to date. Here, a fabrication strategy for embedding high areal density single‐atom Pt sites via a defect engineering approach is demonstrated. Similar to the synergistic mechanism in binuclear homogeneous catalysts, from both experimental and theoretical results, it is proved that electrons would redistribute between the two oxo‐bridged paired Pt sites after hydrogen adsorption on one site, which enables the other Pt site to have high CO oxidation activity at mild‐temperature. The dynamic electronic interaction between neighboring Pt sites is found to be distance dependent. These new SACs with abundant Pt‐O‐Pt paired structures can improve the efficiency of CO chemical purification.
This work investigates the synthesis and CO chemical purification applications of densely populated single‐atom catalysts. Because of electron bridge interaction and cooperative activation of two Pt1 sites, this CO chemical purification technology has a record‐low cost and high CO purity. Furthermore, the Pt1 site is not the active site of the CO oxidation in Pt1/TiO2, but the Pt1‐O‐Pt1 site is.
We have created a facial self-templated method to synthesize three distinct nanostructures, including the unique edge-cut Cu@Ni nanocubes, edge-notched Cu@Ni nanocubes, and mesoporous Cu–Ni nanocages ...by selective wet chemical etching method. Moreover, in the synthesis process, the corners of edge-cut Cu@Ni nanocubes and mesoporous Cu–Ni nanocages can be etched to produce the highly catalytically active (111) facets. Impressively, compared to edge-notched Cu@Ni nanocubes and edge-cut Cu@Ni nanocubes, the Cu–Ni nanocages exhibit higher electrocatalytic activity in the hydrogen evolution reaction (HER) under alkaline conditions. When obtained overpotential is 140 mV, the current density can reach 10 mA cm–2; meanwhile, the corresponding Tafel slope is 79 mV dec–1. Moreover, from the calculation results of density functional theory (DFT), it can be found that the reason why the activity of pure Ni is lower than that of Cu–Ni alloy is that the adsorption energy of the intermediate state (adsorbed H*) is too strong. Meanwhile the Gibbs free-energy (|ΔG H*|) of (111) facets is smaller than that of (100) facets, which brings more active sites or adsorbs more hydrogen.
Methods allowing construction of macroscopic programmed materials in a flexible and efficient fashion are highly desirable. However, the existing approaches are far removed from such materials. A new ...self‐healing‐driven assembly (SHDA) strategy to fabricate various programmed materials by using uniform gel beads (microsize of 212 µm or millimeter size of 4 mm) as building blocks is described here. In virtue of hydrogen bonds and host–guest interactions between gel beads, a series of linear, planar, and 3D beaded assemblies are fabricated via SHDA in microfluidic channels in a continuous and controlled manner. From the perspective of practical applications, the use of gel assemblies is exploited for tissue engineering with controlled cells coculture, as well as light conversion materials toward white‐light‐emitting diodes (WLEDs). The SHDA strategy developed in this study gives a new insight into the facile and rapid fabrication of various programmed materials toward biological tissue and optoelectronic device.
A new microfluidic‐assisted self‐healing‐driven assembly strategy is developed for constructing programmed ordered assemblies in a continuous and controllable fashion by using self‐healing gel beads as building blocks, which allows self‐assembly to be carried out on a macroscopic scale toward tissue materials and light‐emitting diodes devices.
Abstract
The demand for sustainable energy has motivated the development of artificial photosynthesis. Yet the catalyst and reaction interface designs for directly fixing permanent gases (e.g. CO
2
, ...O
2
, N
2
) into liquid fuels are still challenged by slow mass transfer and sluggish catalytic kinetics at the gas-liquid-solid boundary. Here, we report that gas-permeable metal-organic framework (MOF) membranes can modify the electronic structures and catalytic properties of metal single-atoms (SAs) to promote the diffusion, activation, and reduction of gas molecules (e.g. CO
2,
O
2
) and produce liquid fuels under visible light and mild conditions. With Ir SAs as active centers, the defect-engineered MOF (e.g. activated NH
2
-UiO-66) particles can reduce CO
2
to HCOOH with an apparent quantum efficiency (AQE) of 2.51% at 420 nm on the gas-liquid-solid reaction interface. With promoted gas diffusion at the porous gas-solid interfaces, the gas-permeable SA/MOF membranes can directly convert humid CO
2
gas into HCOOH with a near-unity selectivity and a significantly increased AQE of 15.76% at 420 nm. A similar strategy can be applied to the photocatalytic O
2
-to-H
2
O
2
conversions, suggesting the wide applicability of our catalyst and reaction interface designs.
Monodisperse single-crystalline sub-10 nm Pt−Pd nanotetrahedrons (NTs) and nanocubes (NCs) were synthesized with high shape selectivity via one-pot hydrothermal routes with small ions as efficient ...facet-selective agents. These alloy nanocrystals showed facet-dependent enhanced electrocatalytic activity and durability for methanol electrooxidations with commercial Pt/C catalyst as a reference. The (100)-facet-enclosed Pt−Pd NCs demonstrated a higher activity, whereas the (111)-facet-enclosed Pt−Pd NTs exhibited a better durability.
SUMMARY
Although the biochemical and genetic basis of lipid metabolism is clear in Arabidopsis, there is limited information concerning the relevant genes in Glycine max (soybean). To address this ...issue, we constructed three‐dimensional genetic networks using six seed oil‐related traits, 52 lipid metabolism‐related metabolites and 54 294 SNPs in 286 soybean accessions in total. As a result, 284 and 279 candidate genes were found to be significantly associated with seed oil‐related traits and metabolites by phenotypic and metabolic genome‐wide association studies and multi‐omics analyses, respectively. Using minimax concave penalty (MCP) and smoothly clipped absolute deviation (SCAD) analyses, six seed oil‐related traits were found to be significantly related to 31 metabolites. Among the above candidate genes, 36 genes were found to be associated with oil synthesis (27 genes), amino acid synthesis (four genes) and the tricarboxylic acid (TCA) cycle (five genes), and four genes (GmFATB1a, GmPDAT, GmPLDα1 and GmDAGAT1) are already known to be related to oil synthesis. Using this information, 133 three‐dimensional genetic networks were constructed, 24 of which are known, e.g. pyruvate–GmPDAT–GmFATA2–oil content. Using these networks, GmPDAT, GmAGT and GmACP4 reveal the genetic relationships between pyruvate and the three major nutrients, and GmPDAT, GmZF351 and GmPgs1 reveal the genetic relationships between amino acids and seed oil content. In addition, GmCds1, along with average temperature in July and the rainfall from June to September, influence seed oil content across years. This study provides a new approach for the construction of three‐dimensional genetic networks and reveals new information for soybean seed oil improvement and the identification of gene function.
Significance Statement
One hundred and thirty‐three three‐dimensional genetic networks among seed oil‐related traits, lipid metabolism‐related metabolites and genes in soybean were constructed for the first time using phenotypic and metabolic genome‐wide association studies and multi‐omics analyses. These networks were used to try to explain the genetic relationships among seed oil‐related traits, oil synthesis‐related carbon metabolites and oil synthesis‐related amino acids.
A series of 2catenanes has been prepared from di‐NHC building blocks by utilizing solvophobic effects and/or π⋅⋅⋅π stacking interactions. The dinickel naphthobiscarbene complex syn‐1 and the kinked ...biphenyl‐bridged bipyridyl ligand L2 yield the 2catenane 2‐IL(OTf)4 by self‐assembly. Solvophobic effects are pivotal for the formation of the interlocked species. Substitution of the biphenyl‐linker in L2 for a pyromellitic diimide group gave ligand L3, which yielded in combination with syn‐1 the 2catenane 3‐IL(OTf)4. This assembly exhibits enhanced stability in diluted solution, aided by additional π⋅⋅⋅π stacking interactions. The π⋅⋅⋅π stacking was augmented by the introduction of a pyrene bridge between two NHC donors in ligand L4. Di‐NHC precursor H2‐L4(PF6)2 reacts with Ag2O to give the Ag2L422 2catenane 4‐IL(PF6)4, which shows strong π⋅⋅⋅π stacking interactions between the pyrene groups. This assembly was readily converted into the Au2L422 gold species 5‐IL(PF6)4, which exhibits exceptional stability based on the strong π⋅⋅⋅π stacking interactions and the enhanced stability of the Au‐CNHC bonds.
Different effects have been shown to control the formation of 2catenanes with different bridges between pyridine donors. The formation of 2‐IL(OTf)4 is aided by solvophobic effects and 3‐IL(OTf)4 is stabilized by solvophobic effects and π⋅⋅⋅π stacking. The π⋅⋅⋅π stacking between the pyrene groups is essential for the formation of 4‐IL(PF6)4 and 5‐IL(PF6)4, where the enhanced stability of 5‐IL(PF6)4 is based on the more stable Au−CNHC bonds.
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