Abstract
Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, ...we achieve selective oxygen (O
2
) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3
d
orbitals of isolated copper (Cu) sites. Operando X-ray absorption spectroscopy, electron paramagnetic resonance and density-functional theory simulations are used to demonstrate that a Cu(I)O
2
3−
site selectively adsorbs molecular O
2
, forming a rarely reported electrophilic η
2
-O
2
species at 298 K. Assisted by neighbouring Ce(III) cations, η
2
-O
2
is finally reduced to two O
2−
, that create two Cu–O–Ce oxo-bridges at 453 K. The isolated Cu(I)/(II) sites are ten times more active in CO oxidation than CuO clusters, showing a turnover frequency of 0.028 ± 0.003 s
−1
at 373 K and 0.01 bar
P
CO
. The unique electronic structure of Cu(I)O
2
3−
site suggests its potential in selective oxidation.
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•C3N monolayer was adopted as support for HCOOH dehydrogenation SACs.•Twelve TM@C3N SACs were screened by the binding/separation stability of adatoms.•Adsorption property of HCOOH and ...H species was used to evaluate catalytic activity.•Ni@C3N, Pd@C3N, Pt@C3N were screened out with good catalytic activity and selectivity.•Hydrogen production performance is revealed by d-band center, charge and COHP analysis.
Formic acid (HCOOH) is a promising hydrogen carrier. Developing efficient and low-cost catalysts is significant for the application of HCOOH in clean and renewable energy. In this work, a series of single-atom catalysts composed of twelve transition metal single atoms (Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag and Au) supported on a novel carbon-nitrogen material (C3N) were designed and the catalytic performance for HCOOH dehydrogenation was demonstrated using density functional theory. By evaluating the binding strength of TM atoms, the adsorption stability of HCOOH and the hydrogen evolution performance of H species, Ni@C3N, Pd@C3N and Pt@C3N were finally screened out as candidates, on which the HCOO-dehydrogenation pathway is the most preferred. Judging from energetic span, Pd@C3N (0.60 eV) owns the best catalytic activity, while Ni@C3N (1.02 eV) and Pt@C3N (1.12 eV) are also appreciable alternatives compared with Pd(111) (1.23 eV). Through the analysis of catalytic mechanism and electronic structure, the factors influencing reaction activity were revealed. This work enlightens the advantage of C3N-based materials and provides a novel approach for rationally designing high-performance catalysts for hydrogen production from HCOOH.
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•Three kinds of nitrogen-doped graphene supported Pd1 SACs and Pd4 SCCs were designed.•Graphitic N-doped graphene is a good support for single atom or single cluster catalyst.•On ...graphN3 support, the catalytic activity of Pd4 is better than that of Pd1.•Pd4@graphN3 shows excellent HCOOH dehydrogenation activity among the six catalysts.•All Pd1/Pd4@NG catalysts have 100 % H2 selectivity.
Formic acid (FA, HCOOH) is one of the most promising hydrogen carriers. Developing cost-effective dehydrogenation catalyst for formic acid is the key to the application of formic acid as hydrogen storage compound. In this study, we systematically studied the catalytic performance of nitrogen-doped graphene supported Pd1 single-atom and Pd4 single-cluster for dehydrogenation of formic acid by density functional theory calculations. Three types of nitrogen-dopants (pyridinic N, pyrrolic N and graphitic N) were introduced into graphene to determine which N dopant plays an important role in catalytic dehydrogenation of formic acid. The results showed that HCOOH decomposition proceeds via the formate (HCOO) intermediate to yield product CO2 and H2, so all catalysts have 100 % H2 selectivity. On graphN3 support, the catalytic activity of Pd4 single-cluster catalyst (SCC) is better than that of Pd1 single-atom catalyst (SAC), while on pyriN3 and pyrroN3, the catalytic activity of Pd1 SAC is better. Compared with traditional Pd(111), the present SACs and SCCs exhibit higher HCOOH dehydrogenation activity, and Pd4@graphN3 has the best catalytic performance with an energetic span of 0.75 eV, much lower than 1.33 eV of Pd(111). Our work provides an insight into the effects of the coordination environment of N-doped graphene support and active center size on FA dehydrogenation performance.
To develop potential metal–organic frameworks (MOFs) for 2,4,6-trinitrophenol (TNP) detection, an amino-functionalized Zn-MOF, NH2(CH3)2Zn4O(bpt)2(bdc-NH2)0.5·5DMF (where H3bpt = ...biphenyl-3,4′,5-tricarboxylate, H2bdc-NH2 = 2-aminoterephthalic acid, and DMF = N,N-dimethylformamide), has been designed theoretically and synthesized experimentally. Its structure is composed of Zn4O(CO2)7 secondary building units linked by mixed ligands, exhibiting a three-dimensional framework. Fluorescence exploration revealed that the amino-functionalized Zn-MOF shows high selectivity and sensitivity for TNP, which agrees well with the predictions of theoretical simulations. This work provides a suitable means to develop new potential MOFs for TNP detection performance with a combination of experimental and theoretical perspectives.
Hybrid multi-metallic nanocatalysts have attracted increasing attention because of the synergistic effect of metal species and considerably improved catalytic performance, but they often suffer from ...severe sintering and poor stability. Here, we show a facile strategy for preparing subnanometric hybrid bimetallic clusters Pd-M(OH)2 (M = Ni, Co) within silicalite-1 (S-1) zeolite via a hydrothermal synthesis method. The hybrid bimetallic nanocatalysts exhibit excellent shape-selective catalytic performance and superior thermal stability. The incorporation of secondary Ni(OH)2 species in S-1 can considerably increase the catalytic activity of the Pd nanoclusters for the dehydrogenation of formic acid (FA) as a result of the electron-enriched Pd surface and bimetallic interfacial effect. Notably, the 0.8Pd0.2Ni(OH)2@S-1 catalyst affords the highest initial turnover frequency value, up to 5,803 hr−1 toward complete FA decomposition without any additives at 60°C. The superior catalytic properties and excellent stability of the subnanometric hybrid bimetallic clusters confined in zeolites create new prospects for their practical high-performance catalytic application.
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•Synthesis of subnanometric hybrid bimetallic clusters within zeolites•The nanocatalysts possessed excellent activity for hydrogen generation•The nanocatalysts exhibited shape-selective catalytic performance•The nanocatalysts showed superior thermal stability and recyclability
Hybrid multi-metallic nanocatalysts have attracted increasing attention because of the synergistic effect of metal species and considerably improved catalytic activity but often suffer from severe sintering and poor stability. Zeolites are known as ideal supports for confinement synthesis of metal nanoparticles. In this work, subnanometric hybrid Pd-M(OH)2 (M = Ni, Co) clusters encapsulated within purely siliceous zeolites were synthesized via a hydrothermal synthesis method. The hybrid bimetallic nanocatalysts exhibit superior thermal stability at 600°C–700°C and afford the highest initial turnover frequency value, up to 5,803 hr−1 toward complete formic acid decomposition without any additives at 60°C. The hybrid bimetallic nanoclusters confined in zeolites have potential practical application in dehydrogenation of formic acid as a viable and effective chemical hydrogen storage medium for fuel cells, and also raise more possibilities for other important high-performance catalytic reactions.
Subnanometric hybrid bimetallic palladium-transition metal hydroxide clusters are encapsulated within zeolites by using metallic ethylenediamine complexes as precursors under direct hydrothermal conditions. The hybrid bimetallic nanocatalysts exhibit shape-selective catalytic performance, superior thermal stability, as well as exceedingly high dehydrogenation efficiency toward complete formic acid decomposition as a result of the nanoconfinement effect of zeolites as well as the synergistic effect of hybrid metal species.
BiVO4 nanomaterials are potentially applicable in gas sensing, but the sensing performance is limited by the less active sites on the BiVO4 surface. In this work, we propose a strategy to improve the ...gas-sensing performance of BiVO4 by forming ultrathin nanosheets and introducing oxygen vacancies, which increase the surface active sites. Two-dimensional (2D) BiVO4 nanosheets with oxygen vacancies are prepared through a colloidal method with the assistance of nitric acid. Gas sensors based on the oxygen-defective 2D ultrathin BiVO4 nanosheets exhibit an enhanced sensing response, which is 3.4 times higher than those of the sensors based on oxygen-abundant BiVO4 nanosheets. The density functional theory calculation is employed to uncover the promoting effects of oxygen vacancies on enhancing the O2 adsorption capability of BiVO4 nanosheets. This work is not only expected to build a wide range of 2D metal oxide semiconductors with a high gas-sensing performance but also gives an insight into the mechanism of the enhanced response induced by the oxygen vacancies, which will be a guideline for further designing high-performance sensing materials.
Two new isostructural 3D lanthanide–organic frameworks H2N(Me)2 Ln3(OH)(bpt)3(H2O)3 (DMF)2⋅(H2O)4 (1‐Ln; Ln=Sm and Eu) with a 1D channel (25 Å) have been successfully assembled from the rare ...trinuclear Ln3(OH)(COO)9 clusters and biphenyl‐3,4′,5‐tricarboxylic acid (H3bpt) and exhibit high stability towards water in the pH range 3–10. MOF 1‐Eu is a promising luminescent probe for sensing Fe3+ in aqueous solution and is also selective towards rhodamine B (RhB) with a superior adsorption capacity of 735 mg g−1, which is the highest among the reported Ln‐MOFs for RhB removal so far. Periodic DFT calculations further confirmed the selective adsorption of rhodamine B over other dyes.
A superior MOF! Two new Ln–MOFs with an uncommon one‐dimensional channel (25 Å) have been synthesized and show high stability towards water in the pH range 3–10 (see figure). MOF 1‐Eu is a promising luminescent probe for sensing Fe3+ in aqueous solution and is also selective towards rhodamine B with a superior adsorption capacity.
Noble-metal-free catalysts are highly desirable for hydrogen generation from formic acid dehydrogenation. Herein, using first-principles density functional theory calculations, we design a series of ...nickel-anchored nitrogenated holey two-dimensional carbon structures (Nix@C2N, x = 1–3) as formic acid dehydrogenation catalysts. For all Nix@C2N surfaces, the formic acid dehydrogenation preferably proceeds via the formate pathway. The effective barrier continuously decreases for formic acid dehydrogenation while increases for hydrogen formation from Ni1@C2N to Ni3@C2N. The side reaction producing carbon monoxide and water via the carboxyl or formyl pathway cannot occur on Ni1@C2N or Ni2@C2N and is not preferred on Ni3@C2N, and thus, the Nix@C2N catalysts possess excellent selectivity of hydrogen. Notably, the unsaturated nitrogen atom of substrate also participates in the reaction and exhibits synergetic effect with the nickel component in Ni1@C2N and Ni2@C2N. The Gibbs free energetic span analysis predicts that the order of reactivity is Ni2@C2N (0.79 eV) > Ni1@C2N (0.87 eV) > Ni3@C2N (1.23 eV), and the turnover frequency of Nix@C2N is evaluated. The results are compared with the experimental and theoretical reports of some palladium-based catalysts. The present work suggests that the Nix@C2N may be promising noble-metal-free catalysts for formic acid dehydrogenation with high performance and low cost.
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•C2N monolayer acts as stable support for nickel single atom and clusters.•Nix@C2N catalysts achieve better catalytic activity and selectivity than pure palladium.•Nitrogen atoms of C2N participate and facilitate catalytic reactions via synergetic effect.
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•The core-shell structure of PdxCoy@Pd(1 1 1) is stable during HCOOH decomposition.•The atomic composition of Pd-Co core affects the dehydrogenation pathways of ...HCOOH.•PdxCoy@Pd(1 1 1) has better catalytic performance for HCOOH decomposition than Pd(1 1 1).•The introduction of Co into Pd core improves the anti-CO poisoning ability.
The decomposition mechanism of formic acid on three Pd-based core-shell catalysts PdxCoy@Pd(1 1 1) (x:y = 1:3, 1:1 and 3:1) and pure Pd(1 1 1) surfaces has been systematically studied by periodic density functional theory (DFT) calculations. The possible dehydrogenation and dehydration pathways through the HCOO, COOH and HCO intermediates have been identified. It is found that the most favorable dehydrogenation pathways on Pd1Co3@Pd(1 1 1) and PdCo@Pd(1 1 1) are the COOH-mediated pathway, which are different from the HCOO-mediated pathway on Pd3Co1@Pd(1 1 1) and Pd(1 1 1). The increase of Co content in the Pd-Co core inhibits HCOOH dehydrogenation, but promotes the H-H coupling to form H2, and improves the anti-CO poisoning ability of the catalysts. Accordingly, three bimetallic PdxCoy@Pd catalysts exhibit better overall catalytic activity and product selectivity toward H2 + CO2 than pure Pd(1 1 1), especially PdCo@Pd(1 1 1) has the best catalytic performance for HCOOH decomposition. The present calculations show that a suitable Co composition in Pd-Co core plays an important role in tuning the catalytic performance, which provides a theoretical guideline to design high performance bimetallic core-shell catalysts for other dehydrogenation reactions.
To tackle the issue of low sulfur utilization and inferior cycle stability of sulfur cathode, we first report a new perovskite-type La0.6Sr0.4CoO3-δ (LSC) immobilizer to anchor the intermediate ...polysulfides via chemical interaction. The experimental results and theoretical calculations demonstrate that Sr doping results in valence variation in Co along with oxygen vacancy; The Co ions with mixed valence have strong adsorption to the polysulfide ions while the existence of oxygen vacancy enhances the binding strength between Li2S4 and LSC. Based on LSC, a dual coxial LSC/S@C nanocable is successfully designed and fabricated. With a sulfur loading of 2.1mgcm−2, the LSC/S@C cathodes demonstrate a high reversible capacity of 996mAhg−1 at 0.5C and an outstanding cycle stability with only 0.039% capacity fade per cycle over 400 cycles. Even with a high sulfur loading of 5.4mgcm−2, the LSC/S@C cathode can still deliver similar sulfur utilization and excellent cycling stability. The excellent cycle stability benefits from the chemical interaction between LSC and polysulfides, and the physical entrapment of the carbon shell. Moreover, the highly conductive LSC@C host and the porous interconnected fiber web-like architecture facilitate the mass transfer during charge/discharge process synchronously.
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•A novel perovskite La0.6Sr0.4CoO3-δ (LSC) immobilizer is firstly introduced into the Li-S system.•A dual core-shell structure of LSC/S@C cathode have successfully designed and fabricated.•The chemical bond between LSC and polysulfide is confirmed by the DFT calculation, XPS spectra and iodometric titrations.•With a high sulfur loading of 5.4mgcm−2, the LSC/S@C cathode deliver comparable cycling stability.
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