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Abstract: The catalytic activities of supported metal nanoparticles can be tuned by appropriate design of synthesis strategies. Each step in a catalyst synthesis method can play an important role in preparing the most efficient catalyst. Here we report the careful manipulation of the post-synthetic heat treatment procedure—together with control over the metal loading—to prepare a highly efficient 0.2 wt% Pt/TiO2 catalyst for the chemoselective hydrogenation of 3-nitrostyrene. For Pt/TiO2 catalysts with 0.2 and 0.5 wt% loading levels, reduction at 450 °C induces the coverage of TiOx over Pt nanoparticles through a strong metal–support interaction, which is detrimental to their catalytic activities. However, this can be avoided by following calcination treatment with reduction (both at 450 °C), allowing us to prepare an exceptionally active catalyst. Detailed characterization has revealed that the peripheral sites at the Pt/TiO2 interface are the most likely active sites for this hydrogenation reaction.

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Abstract: As a new class of sustainable carbon material, the term “carbon dots” represents an “umbrella term” as there are many types of materials included. We employ a broad range of techniques to develop understanding on hydrothermally synthesized carbon dots and show how fine tuning the structural features using simple reduction/oxidation reactions can drastically affect their excited state properties. Structural and spectroscopic studies found that photoluminescence originates from direct excitation of localized fluorophores involving oxygen functional groups, while the excitation at graphene‐like features leads to ultrafast phonon‐assisted relaxation and largely quenches the fluorescent quantum yields. This is arguably the first to identify the dynamics of photoluminescence including Stokes’ shift formation, allowing us to fully resolve the relaxation pathways in these carbon dots. The comprehensive investigation sheds light on how understanding the excited state relaxation processes in different carbon structure is crucial for tuning the optical properties for any potential commercial applications.

Open Access

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Abstract: Iron oxide nano-crystals 0.1–1.1 μm in diameter were generated on sulfur-doped amorphous carbon surfaces by electron beam irradiation of the novel 13e− high-spin complex [Fe(4-methyl-1,2-benzenedithiolate)2][NHEt3] encapsulated in a triblock copolymer. Possible relevance to iron nano-mineralization from Fe–S ferredoxin proteins and iron dysregulation in neurological disorders is discussed.

Open Access

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Abstract: Wet impregnation is broadly applied for the synthesis of carbon-supported metal/metal oxide nanostructures because of its high flexibility, simplicity and low cost. By contrast, impregnated catalysts are typified by a usually undesired nanostructural and morphological heterogeneity of the supported phase resulting from a poor stabilization at the support surface. This study on graphite-supported Fe-based materials from Fe nitrate precursor is concerned with the understanding of the chemistry that dictates during the multistep synthesis, which is key to designing structurally homogeneous catalysts. By means of core-level X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy and atomic resolution electron microscopy, we found not only a large variety of particles sizes and morphologies but also chemical phases. Herein, thermally stable single atoms and few atoms clusters are identified together with large agglomerates of an oxy-hydroxide ferrihydrite-like phase. Moreover, the thermally induced phase transformation of the initially poorly ordered oxy-hydroxide phase into several oxide phases is revealed, together with the existence of thermally stable N impurities retained in the structure as Fe–N–O bonds. The nature of the interactions with the support and the structural dynamics induced by the thermal treatment rationalize the high heterogeneity observed in these catalysts.

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Abstract: Industrial olefin metathesis catalysts generally suffer from low reaction rates and require harsh reaction conditions for moderate activities. This is due to their inability to prevent metathesis active sites (MAS) from aggregation and their intrinsic poor adsorption and activation of olefin molecules. Here, isolated tungstate species as single molecular MAS is immobilized inside zeolite pores by Brønsted acid sites (BAS) on the inner surface. It is demonstrated for the first time that unoccupied BAS in atomic proximity to MAS enhance olefin adsorption and greatly facilitate the formation of metallocycle intermediates in a stereospecific manner. Thus, effective cooperative catalysis takes place over the BAS-MAS pair. In consequence, for the cross-metathesis of ethene and trans-2-butene to propene, under the same mild reaction conditions, the propene production rate over WOx/USY is ca. 7,300 times that over the industrial WO3/SiO2 based catalyst. A propene yield up to 79% (80% selectivity) without observable deactivation was obtained over WOx/USY for a wide range of reaction conditions.