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Direct coupling of alkanes via C−H activation of terminal methyl groups has acquired tremendous interests both scientifically and technically. Herein we present the results of linear alkane-coupling at the step edges of Cu surfaces at modulated temperatures. Combining the observations of scanning tunneling microscopy (STM) with density functional theory plus dispersion (DFT-D) calculations, we elucidate the mechanism of the reaction and demonstrate that the low activation barrier relies on heterogeneous catalysis at the upper step edges, where low-coordinated surface atoms are present. We further reveal the generality of the reaction, so that it can be applied on the step edges of different facets of surfaces. [ABSTRACT FROM AUTHOR]

• Supported bimetallic catalysts typically possess superior performances than monometal catalysts and the impregnation method has been widely applied for the bimetallic catalyst preparations. • Impregnation sequences could play their significant roles on the physical and chemical properties of supported bimetallic catalysts. • A host of characterizations from impregnation sequential effects were briefly evaluated by reviewing the recent representative literatures. • The investigation of the nature of active sites and the structural dynamics on bimetallic catalysts are prospected accordingly to enhance the fundamental understanding of sequential influences. • The appropriate measurement of reaction rates is much required to compare the bimetallic catalysts that are prepared by different sequences of impregnations. Supported bimetallic catalysts have been paid great attention regarding their excellent catalytic performances in chemical process. Notably, comparing to monometallic catalysts, the synergetic properties of dual-metal-based materials demonstrate unique physiochemical functionalities that single metal materials do not possess. The preparation of supported bimetallic materials is widely conducted with applying the impregnation method because of the straightforward and inexpensive technique. Wherein, the impregnation of dual metals on support could either undergo co-impregnation or sequential impregnations. It has been frequently reported that there are substantial differences in physiochemical properties and catalyst performances by impregnation sequences. Specifically, during the investigation of various sequential impregnated bimetallic catalysts, a host of characterization strategies are employed to compare the physical and chemical properties that play vital role to impact the catalyst activity/selectivity/stability. However, it is still not well understood regarding the impregnation sequential effects, such as the nature of bimetallic active sites and the dynamics of bimetallic surface structures along with reaction progress. This presenting perspective article is devoted to take a succinct review regarding the general sequential impacts on the physiochemical properties and further profoundly address the research outlook in this topic. [Display omitted]. [ABSTRACT FROM AUTHOR]

The standard thermite reaction enthalpies (Δ r H m θ ) for seven metal oxides were theoretically analyzed using density functional theory (DFT) under five different functional levels, and the results were compared with experimental values. Through the comparison of the linear fitting constants, mean error and root mean square error, the Perdew-Wang functional within the framework of local density approximation (LDA-PWC) and Perdew-Burke-Ernzerhof exchange-correlation functional within the framework of generalized gradient approximation (GGA-PBE) were selected to further calculate the thermite reaction enthalpies for metal composite oxides (MCOs). According to the Kirchhoff formula, the standard molar reaction enthalpies for these MCOs were obtained and their standard molar enthalpies of formation (Δ f H m θ ) were finally calculated. The results indicated that GGA-PBE is the most suitable one out of the total five methods to calculate these oxides. Tungstate crystals present the maximum deviation of the enthalpies of thermite reactions for MCOs and these of their physical metal oxide mixtures, but ferrite crystals are the minimum. The correlation coefficients are all above 0.95, meaning linear fitting results are very precise. And the molar enthalpies of formation for NiMoO 4 , CuMoO 4 , PbZrO 3 ( Pm/3m ), PbZrO 3 ( PBA2 ), PbZrO 3 ( PBam ), MgZrO 3 , CdZrO 3 , MnZrO 3 , CuWO 4 and Fe 2 WO 6 were first obtained as −1078.75, −1058.45, −1343.87, −1266.54, −1342.29, −1333.03, −1210.43, −1388.05, −1131.07 and − 1860.11 kJ·mol −1 , respectively. [ABSTRACT FROM AUTHOR]

• A microkinetic model combining oxygen supply and catalysis was established for Fe 2 O 3. • The influence of TMs-doping in Fe 2 O 3 on oxygen carriers was systematically studied. • Ni-doping in Fe 2 O 3 has been confirmed to enhance the formation rate and the selectivity of CO. The rate-matching between oxygen migration and surface catalytic reaction of oxygen carrier (OC) is a critical determinant for the reaction selectivity of the chemical looping reforming (CLR) of methane. However, the theoretical mechanism behind this rate-matching relationship is still unclear. Herein, we propose to use density functional theory (DFT) combined with microkinetic simulations to establish a model integrating the methane oxidation reactions with oxygen migration kinetics on α-Fe 2 O 3 oxygen carrier. Our calculated results reveal that the transition metals (TMs)-doping such as Co, Ni, and Cu after Fe element in the periodic table can accelerate the oxygen migration rate as it promotes the upshift of the O p -band center. Moreover, a suitable oxygen migration energy barrier of about 1.0 eV is helpful to enhance the harmonization of α-Fe 2 O 3 oxygen migration and surface catalytic reactions. Based on this, Ni-doping in α-Fe 2 O 3 is predicted to be able to enhance the oxygen migration rate to match the rate of first-step methane dissociation, thereby simultaneously improving the reaction rate and the selectivity in the CLR of methane to syngas. These results could help to understand the relationship between oxygen migration and surface catalytic reaction rates and pave the way for the rational design of metal oxide oxygen carriers. [ABSTRACT FROM AUTHOR]