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A robust immobilization strategy is proposed by the self-assembly of POSS and TiCl 4 molecules, where a flexible double-Ti structure shows the most reduced energy barrier for ethylene insertion. [Display omitted] • A highly active molecular catalyst toward ethylene polymerization was synthesized according to the self-assembly of POSS and TiCl 4. • A flexible double-Ti structure coordinated to Si-O-Si shows the most reduced energy barrier for ethylene insertion. • Catalytic nanoparticles show robust resistance to H 2 , enhanced incorporation of comonomer, and reduced entanglements of the synthesized polymer. Heterogeneous catalysis plays a crucial role in industrial olefin polymerization. Mechanistic understanding and optimization of Ziegler-Natta (ZN) catalyst are limited by the considerable complexity resulting from the multiple ingredients and complicated structures. Re-designing ZN catalytic systems with reduced complexity and adequate performance is of great interest. Here, we show that self-assembled polyhedral oligomeric silsesquioxane (POSS)@TiCl 4 nanoparticles can effectively immobilize TiCl 4 molecules in n -heptane solution, achieving the exceptional utilization of active centres. This uncomplicated system exhibits heterogeneous-like catalytic performance in ethylene polymerization, featured by high activities, fouling-free polymerization and a series of desirable properties of the nascent polymers such as reduced entanglement and spherical morphology. In addition, these catalytic nanoparticles show robust resistance to H 2 , and enhanced incorporation of comonomer towards ethylene/1-hexene copolymerization. By using DFT calculations the possible structures of the Ti active centres are proposed, of which a flexible double-Ti structure coordinated to Si-O-Si shows the most reduced energy barrier for ethylene insertion. [ABSTRACT FROM AUTHOR]

The Ti immobilization process is directly modulated by the THF migration, which reduces the aggregation of TiCl 4 and enhances the formation of active species. [Display omitted] • Formation mechanism of the active species are traced by the in-situ spectra. • Active species distribution of the Ziegler-Natta catalyst is modulated by the THF migration. • The polyethylene with a narrow distribution is synthesized with a high activity owing to the synchronous migration of THF and immobilization of TiCl 4. Manipulating the interplay between electron donor and catalytic species is a major approach of optimizing Ziegler-Natta catalysts. To this end, it is essential to reveal the correlation between the involved dynamic processes. In this work, a greatly enhanced mobility of the internal donor tetrahydrofuran (THF) is realized even at room temperature in the MgCl 2 substrate modified with MgCl functionalized polyhedral oligomeric silsesquioxane (POSS-MgCl). A series of spectroscopic characterizations evidence that, thanks to the high mobility of THF, the immobilization of catalytic Ti species and the migration of THF occurs synchronously and leads to a nearly homogenous distribution of Ti sites. In addition, the incorporation of POSS-MgCl promotes the formation of 4-coordinated Mg sites in the substrate. The modified Ziegler-Natta catalyst shows the remarkable performance toward ethylene polymerization, featured by the high catalytic activity (21.6 × 106 g PE(mol Ti·h)−1) as well as a narrow polydiversity index (3.1) of the synthesized polyethylene. Based on these results, we propose that the Ti immobilization process is directly modulated by the THF migration in this system, which reduces the aggregation of TiCl 4 and enhances the formation of active species. [ABSTRACT FROM AUTHOR]

[Display omitted] • PtRu catalysts composed of Pt and RuO 2 are synthesized via cyclic electrodeposition. • PtRu catalyst shows unprecedented performance for ECH of phenol to cyclohexanol. • PtRu catalyst possesses outstanding reusability in acidic electrolyte. • The activation of phenol is observed via in situ Raman spectroscopy. • The direct reduction mechanism with proton-coupled electron transfer is proposed. Electrocatalytic hydrogenation (ECH) of phenol has been recognized as a promising route towards facile and green production of cyclohexanol. However, the practical application is hindered by product selectivity and catalyst durability. Herein, a series of PtRu electrocatalysts composed of metallic Pt0 and RuO 2 species are in situ fabricated on carbon paper via cyclic electrodeposition, showing outstanding activity and stability for ECH of phenol. At ambient temperature and a current density of 10 mA cm−2, the optimal Pt3Ru3 catalyst achieves a 100 % selectivity to cyclohexanol at a 100 % conversion of phenol in 0.1 M H 2 SO 4. At 100 mA cm−2, Pt3Ru3 achieves an outstanding faradaic efficiency of ∼87 % and a cyclohexanol production of 52.6 mg cm−2 h−1. Two parallel ECH pathways from phenol to cyclohexanol are identified. In situ Raman spectroscopy and kinetic study reveal that phenol could be hydrogenated over Pt3Ru3 in acidic electrolyte via proton-coupled electron transfer with the destruction of conjugated π bond of aromatic ring. This work offers an effective approach for facile construction of durable electrode material and an efficient electrochemical strategy for phenol hydrogenation. [ABSTRACT FROM AUTHOR]

Plasma-catalytic WGS was upgraded under 150 °C low temperature and the underlying mechanisms were proposed by Experimental and theoretical results. [Display omitted] • Plasma-catalytic WGS reaction achieves 96% CO conversion at 150 °C. • In-situ experimental results reveal the participation of gaseous radicals. • DFT calculations propose a WGS reaction mechanism under plasma condition. • Microkinetic model clarify the enhancement by radicals and vibrational excitation. Low temperature WGS reaction is kinetically limited though it is thermodynamically favored. Herein, an outstanding synergistic effect between dielectric barrier discharge (DBD) plasma and non-precious CuO x /CeO 2 catalysts was observed to robustly accelerate the water gas shift (WGS) reaction at 150 °C (increase from 6% to 96% after plasma on). The apparent activation energy of the reaction was remarkablly diminished by plasma (69.6 to 15.0 kJ/mol). In-situ characterization experiments (e. g. OES and DRIFTS) revealed that the OH radicals generated by plasma-induced H 2 O dissociation was found to participate in the WGS reaction. In the furtherly study in DFT calculation and microkinetic modelling investigation, the OH radicals were proved to be one of the reasons for the giant increase in reaction rate. Besides, the vibrational excitation of reactants (e. g. CO) promoted by plasma could also reduce the reaction barriers of some crucial elementary reactions, thus accelerating the reaction rate. [ABSTRACT FROM AUTHOR]

Single-atomic gold decorated CdS nanocatalyst for atom transfer radical addition of alkenes under blue-LED light. [Display omitted] • The Au SASs decorated CdS nanocatalyst was synthesized via a photoreduction strategy. • The host (CdS)-guest (Au) electron transfer mechanism was formed on this nanocatalyst. • ATRA reactions of alkenes can be achieved in high yields under blue-LED-induction. • The excellent selectivity is presented on this nanocatalyst. Atom transfer radical addition (ATRA) is commonly applied to introduce perfluoroalkyl groups into organic molecules, but it often suffers from harsh reaction condition, poor yield and expensive catalyst usage for practical application. Light-induced ATRA reaction is of great significance due to its merits of mild reaction condition and easy operation, but it is generally difficult to achieve high yield because of the lack of ideal photosensitizers. Herein, an Au single-atom sites (SASs) decorated hexagonal cadmium sulfide (CdS) nanocatalyst (Cat CdS-Au) was synthesized to catalyze ATRA reaction under mild blue-LED-induction. As a result, the synergetic effect of CdS-Au interaction enhanced the optical properties and promoted the host (CdS)-guest (Au) electron transfer, leading to high ATRA yields (88–98%) and excellent selectivity even choosing different alkene substrates, which is remarkably superior over existing reaction systems (60–90% yields) ever reported in literatures. The present work sheds light on realizing high ATRA reaction yield via a green and high-efficient synthetic strategy. [ABSTRACT FROM AUTHOR]

An in-situ exsolution strategy is proposed for constructing interfacial Ni0/Niδ+ sites to regulate the reaction pathways of selective hydrogenation reaction. Benefiting from the interfacial Ni0/Niδ+ sites, the hydrogen dissociation is promoted and the selective activation of monoester group of DMO is achieved via a tilted adsorption configuration. Such activation behaviours steer the reaction pathway of DMO to desired product MG. [Display omitted] • In situ exsolution strategy for constructing the interfacial Ni0/Niδ+ active sites. • Selectively activated monoester group of DMO via tilted adsorption configuration. • Hydrogen dissociation is boosted on interfacial Ni0/Niδ+ sites. • Hydrogenation reaction path of DMO is regulated to target MG on Ni0/Niδ+ sites. Regulating the selectivity of reaction pathways to desirable products via controlling adsorption/activation behaviors towards reactants is significant for the design of excellent catalysts for selective hydrogenation but remains challenging. Exemplified with dimethyl oxalate (DMO) hydrogenation, we herein propose an in situ exsolution strategy for constructing interfacial Ni0/Niδ+ sites by using pre-synthesized Ni phyllosilicate as the precursor to control the reaction pathways of selective hydrogenation. Structural characterizations, including in situ spectroscopic and isotopic studies, and theoretical calculations elucidate that the interfacial Ni0/Niδ+ sites can selectively activate monoester group of DMO via a tilted adsorption configuration and hence boost hydrogen dissociation. With such activation behaviors the reaction pathway is steered to methyl glycolate, other than the pathway to ethylene glycol on the reference active sites where both ester groups are activated and methyl formate is formed via breaking the C–C bond of DMO. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal particle sizes on ceria-supported catalysts are difficult to measure. • CO 2 can passivate a ceria surface against carbonate formation during exposure to CO. • Pd particle sizes measured were consistent with CO oxidation kinetics. Characterizing ceria-containing catalysts via common characterization techniques can be challenging. CO chemisorption is usually used to measure catalyst dispersion. However, the reaction between CO and ceria lattice oxygen leads to significant carbonate formation, resulting in an overestimation of the CO uptake and metal dispersion. Here, we propose a modified method to characterize ceria-containing catalysts which involves exposing the catalyst to CO 2 prior CO adsorption to prevent further carbonate formation during CO chemisorption. We tested this method on Pd/CeO 2 catalysts characterized by different ceria particle sizes and validated it via DRIFTS and CO oxidation kinetics. Validation conducted using CO oxidation kinetics showed that the TOFs derived by normalizing the reaction rates by the interfacial sites, which are the active sites, are similar for all the catalysts under investigation. Our results show that CO 2 -CO chemisorption can be a reliable technique for estimating metal dispersion of ceria-supported catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni and I substitutionally codoped TiO 2 phase junction was synthesized. • The photocalcatalysis for CO 2 reduction in water vapor was accomplished. • The selectivity of CH 4 product reached above 98%. • The electron transfer was enhanced by Ni(III)/Ni(II) pair. • The CO 2 adsorption mode was changed by the doping Ni/I. Ni and I co-doped TiO 2 nanoparticles with mixed anatase-brookite phase (Ni/I-TiO 2) were synthesized by the hydrothermal-calcination method for photocatalytic CO 2 reduction with H 2 O vapor. The I and Ni co-doping, anatase-brookite phase junction, as well as the presence of Ti(III) and Ni(III) endowed the catalyst with promoted visible light absorption, increased reduction ability of photogenerated electrons, facilitated charge separation and migration along with modulated CO 2 adsorption mode and capacity, ultimately resulting in boosted photocatalytic activity and product selectivity as compared with those of pure TiO 2. The CO, CH 4 and O 2 yields of the optimized Ni/I-TiO 2 reached 3.49, 158.25 and 246.30 μmol/g cat after 15 h of light illumination, which decreased slightly after 9 cycles, and the product selectivity was above 98 % for photocatalytic reduction of CO 2 to CH 4 with Ni and I co-doping. The in-situ FTIR results with the observation of CH 3 O and CH 3 intermediates confirmed CH 4 formation, and the possible mechanism of photocatalytic CO 2 reduction over Ni/I-TiO 2 was elucidated. This work provides new insights to pursue efficient catalysts for the selective photocatalytic CO 2 reduction to CH 4. [ABSTRACT FROM AUTHOR]