Lichen Liu

Complete Photocatalytic Reduction of CO2 to Methane by H2 under Solar Light Irradiation

Nickel supported on silica-alumina is an efficient and reusable photocatalyst for the reduction of CO2 to methane by H2, reaching selectivity above 95% at CO2 conversion over 90%. Although NiO behaves similarly, it undergoes a gradual deactivation upon reuse. About 26% of the photocatalytic activity of Ni/silica-alumina under solar light derives from the visible light photoresponse.

Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D

Single metal atoms and metal clusters have attracted much attention thanks to their advantageous capabilities as heterogeneous catalysts. However, the generation of stable single atoms and clusters on a solid support is still challenging. Herein, we report a new strategy for the generation of single Pt atoms and Pt clusters with exceptionally high thermal stability, formed within purely siliceous MCM-22 during the growth of a two-dimensional zeolite into three dimensions. These subnanometric Pt species are stabilized by MCM-22, even after treatment in air up to 540 °C. Furthermore, these stable Pt species confined within internal framework cavities show size-selective catalysis for the hydrogenation of alkenes. High-temperature oxidation-reduction treatments result in the growth of encapsulated Pt species to small nanoparticles in the approximate size range of 1 to 2 nm. The stability and catalytic activity of encapsulated Pt species is also reflected in the dehydrogenation of propane to propylene.

Stabilized Naked Sub-nanometric Cu Clusters within a Polymeric Film Catalyze C–N, C–C, C–O, C–S, and C–P Bond-Forming Reactions

Sub-nanometric Cu clusters formed by endogenous reduction of Cu salts and Cu nanoparticles are active and selective catalysts for C-N, C-C, C-O, C-S, and C-P bond-forming reactions. Sub-nanometric Cu clusters have also been generated within a polymeric film and stored with full stability for months. In this way, they are ready to be used on demand and maintain high activity (TONs up to 10(4)) and selectivity for the above reactions. A potential mechanism for the formation of the sub-nanometric clusters and their electronic nature is presented.

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.

Evolution and stabilization of subnanometric metal species in confined space by in situ TEM

Understanding the behavior and dynamic structural transformation of subnanometric metal species under reaction conditions will be helpful for understanding catalytic phenomena and for developing more efficient and stable catalysts based on single atoms and clusters. In this work, the evolution and stabilization of subnanometric Pt species confined in MCM-22 zeolite has been studied by in situ transmission electron microscopy (TEM). By correlating the results from in situ TEM studies and the results obtained in a continuous fix-bed reactor, it has been possible to delimitate the factors that control the dynamic agglomeration and redispersion behavior of metal species under reaction conditions. The dynamic reversible transformation between atomically dispersed Pt species and clusters/nanoparticles during CO oxidation at different temperatures has been elucidated. It has also been confirmed that subnanometric Pt clusters can be stabilized in MCM-22 crystallites during NO reduction with CO and H2.Understanding the behavior and structural transformation of metal species under reaction conditions is instrumental for developing more efficient and stable catalysts. Here, the authors reveal the evolution and stabilization of subnanometric Pt species confined in MCM-22 zeolite using in situ transmission electron microscopy.

Correction to “Stabilized Naked Sub-nanometric Cu Clusters within a Polymeric Film Catalyze C–N, C–C, C–O, C–S, and C–P Bond-Forming Reactions”

Page 3894. The first author’s surname should be “OliverMeseguer” (just one “s”). It is shown correctly in the list of authors here and on the title page of the revised Supporting Information file. Page 3899. In the Experimental Section, Typical Reaction Procedure, “diethyl ether” was used, not “dimethyl ether” (twice, lines 8 and 10 in the paragraph). The complete third sentence of this section should read as follows: “The vial was sealed, and the resulting mixture was placed in a pre-heated oil bath at 135 °C and magnetically stirred. After 24 h, slow addition of diethyl ether or dichloromethane (5 mL) and water (6 mL), separation of the organic layer, and two extractions of the aqueous layer with diethyl ether or dichloromethane were carried out before the combined organic layers were dried over MgSO4 and then filtered.” ■ ASSOCIATED CONTENT *S Supporting Information Additional Figures S1−S20, experimental procedures, and compound characterization, including NMR spectra (with title page corrected). The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.5b03889. Addition/Correction

Retracted article: Synthesis of Pt@TiO2@MnOx hollow spheres with high spatial charge separation efficiency for photocatalytic overall water splitting

We, the named authors, hereby wholly retract this Journal of Materials Chemistry A article due to the subsequent realisation that the O2 evolution rates reported and summarised in Fig. 5 cannot be repeated in the Valencia labs. However, the H2 evolution rates can still be reproduced. Because the oxidation products are mainly radicals or H2O2, we do not observe much O2 evolved. In addition, we also find that the O2 evolution rates seem to be related to the activity test equipment (the Hg lamp we used and the additives in H2O). Signed: Lichen Liu, Weixin Zou, Xianrui Gu, Chengyan Ge, Yu Deng, Changjin Tang, Fei Gao, Lin Dong and Avelino Corma, February 2014. Retraction endorsed by Liz Dunn, Managing Editor, Journal of Materials Chemistry A. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.