Search

Realizing the full potential of oxide‐supported single‐atom metal catalysts (SACs) is key to successfully bridge the gap between the fields of homogeneous and heterogeneous catalysis. Here we show that the one‐pot combination of Ru1/CeO2 and Rh1/CeO2 SACs enables a highly selective olefin isomerization‐hydrosilylation tandem process, hitherto restricted to molecular catalysts in solution. Individually, monoatomic Ru and Rh sites show a remarkable reaction specificity for olefin double‐bond migration and anti‐Markovnikov α‐olefin hydrosilylation, respectively. First‐principles DFT calculations ascribe such selectivity to differences in the binding strength of the olefin substrate to the monoatomic metal centers. The single‐pot cooperation of the two SACs allows the production of terminal organosilane compounds with high regio‐selectivity (>95 %) even from industrially‐relevant complex mixtures of terminal and internal olefins, alongside a straightforward catalyst recycling and reuse. These results demonstrate the significance of oxide‐supported single‐atom metal catalysts in tandem catalytic reactions, which are central for the intensification of chemical processes. [ABSTRACT FROM AUTHOR]

Hexagonal-shaped nanoplates (HNPs) of MoS2 on vertically aligned carbon nanotubes (CNTs) over a patterned area (a circular area of 1 cm2 diameter) are produced by chemical vapor deposition technique. With an optimized initial Mo film thickness, a uniform coverage of MoS2 HNPs with a thickness around 20 nm is achieved. The results confirm that the CNT template plays an important role in the MoS2 HNPs growth. Each MoS2 HNP consists of abundant exposed edges, interesting for sensing and catalysis applications. High crystallinity and quality of the as-produced material are revealed by X-ray photoelectron and Raman spectroscopies. Furthermore, NO2 gas-sensing studies show better sensitivity and recovery for MoS2/CNT samples as compared to pristine CNTs. The detection of NO2 gas in a few tens of parts per million to a few hundreds of parts per billion range, at room temperature, is achieved. Density-functional theory calculation indicates that the exposed edges of MoS2 play a significant role in the NO2 sensing as compared to horizontally aligned MoS2 layers. The present report can promote the research toward the fabrication of efficient and reliable MoS2-based hybrid materials for toxic gas-sensing applications for air quality monitoring in various environments. [ABSTRACT FROM AUTHOR]

Environmental degradation of transition metal disulfides (TMDs) is a key stumbling block in a range of applications. We show that a simple one-pot non-covalent pyrene coating process protects TMDs from both photoinduced oxidation and environmental aging. Pyrene is immobilized non-covalently on the basal plane of exfoliated MoS2 and WS2. The optical properties of TMD/pyrene are assessed via electronic absorption and fluorescence emission spectroscopy. High-resolution scanning transmission electron microscopy coupled with electron energy loss spectroscopy confirms extensive pyrene surface coverage, with density functional theory calculations suggesting a strongly bound stable parallel-stacked pyrene coverage of ~2–3 layers on the TMD surfaces. Raman spectroscopy of exfoliated TMDs while irradiating at 0.9 mW/4 μm2 under ambient conditions shows new and strong Raman bands due to oxidized states of Mo and W. Yet remarkably, under the same exposure conditions TMD/pyrene remain unperturbed. The current findings demonstrate that pyrene physisorbed on MoS2 and WS2 acts as an environmental barrier, preventing oxidative surface reactions in the TMDs catalyzed by moisture, air, and assisted by laser irradiation. Raman spectroscopy confirms that the hybrid materials stored under ambient conditions for two years remained structurally unaltered, corroborating the beneficial role of pyrene for not only hindering oxidation but also inhibiting aging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tunable size of CoS 2 cocatalyst are deposited on the surface of g-C 3 N 4. • The activity of photocatalyst is related to the size of cocatalyst. • CoS 2 /g-C 3 N 4 photocatalyst has activity close to that of Pt/g-C 3 N 4 photocatalyst. The main goal of researchers is to obtain cheap cocatalysts that can promote the photocatalytic activity of catalysts. In this work, a series of CoS 2 /g-C 3 N 4 (denoted as CoS 2 /CN) composite photocatalysts were synthesized by photodepositing CoS 2 on g-C 3 N 4 surface. The size of CoS 2 species could be tuned from single-atom to nanometer scale, which had effect on photocatalysis. The 5CoS 2 /CN sample with proper nano size of CoS 2 cocatalyst had the best photocatalytic performance (1707.19 μmol g−1h−1) in producing H 2 under visible light irradiation (λ > 420 nm). Its photocatalytic activity was about 1434.6 times higher than that of pure g-C 3 N 4 and almost equal with that of Pt/CN catalyst (1799.54 μmol g−1h−1). The Density Functional Theory (DFT) calculation results further suggested that the ability of accumulating the electrons of the cocatalyst was based on the size effect of CoS 2 , and the proper size of the cocatalyst efficiently promoted the separation of photogenerated electron-hole pairs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomic Ce doping is successfully achieved in α-Fe 2 O 3 nanosheets through a hydrothermal method. • The effect of Ce doping in α-Fe 2 O 3 (0 0 1) on NH 3 -SCR reaction is elucidated on atomic level. • A new type of active site based on transient frustrated Lewis pair (TFLP) is firstly proposed. • The mechanistic role of TFLP sites in the NH 3 -SCR reaction is clearly disclosed by DFT calculations. Solid catalysts based on surface frustrated Lewis pairs (FLPs) are emerging materials for the activation of a variety of molecules, such as H 2 , CO 2 and N 2. In the prior works, the FLP sites are already formed in the starting catalysts and the acid and basic sites remain separated during the catalytic cycle. In this work, a new type of reactive site based on transient frustrated Lewis pairs (TFLPs) is proposed to explain the catalytic properties of single-atom Ce-doped α-Fe 2 O 3 (0 0 1) surface for selective reduction of NO x by NH 3. The TFLP sites are formed during the process of the activation of reactants (NH 3 and NO), and will disappear due to the structural reconstruction at the end of the catalytic cycle. By combining the DFT calculations and experimental results, it is inferred that the TFLP sites account for the variation of the preferred reaction pathways on α-Fe 2 O 3 (0 0 1) surface. [ABSTRACT FROM AUTHOR]