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• CH 4 direct dehydrogenation is preferred on Ni. • OH-assisted dehydrogenation of CH 4 is favored on Pt and Ni@Pt. • CO 2 direct dissociation is more favorable than H-assisted way on Ni. • H-assisted CO 2 dissociation is the dominant way on Pt and Ni@Pt. CO 2 reforming of methane (DRM) is a promising reaction for the carbon cycle in nature. Ni was found to be active in this process. However, single component Ni catalysts cannot meet the stability, activity and selectivity demands simultaneously. This paper presents a systematical density functional theory study to investigate the catalytic performance of Ni@Pt(1 1 1) core-shell surface compared with Ni(1 1 1) and Pt(1 1 1) in methane dry reforming. Two ways of O* and OH* assisted CH 4 dehydrogenation are considered in present work. CH 4 direct dissociation is more favored on Ni, while OH*-assisted CH 4 dehydrogenation is more competitive to proceed on Pt and Ni@Pt compared with direct way. Furthermore, Ni@Pt provides much less energy-demanding pathways for both CH and C oxidation, under the assistance of O* or OH*. Therefore, CH is much easier to be oxidized rather than decomposition into carbon on this surface, meanwhile, it is beneficial for carbon elimination and shows promising anti-carbon formation performance. Finally, free energy profiles are plotted at 1000 K and dominant reaction mechanisms of DRM conditions are proposed on three surfaces, respectively. On Ni(1 1 1), O* generated from CO 2 direct dissociation could provide dominant oxidant for CH* oxidation, while on Pt(1 1 1) and Ni@Pt, OH* originated from CO 2 H-assisted dissociation acted as the major oxidant for CH* oxidation. This work sheds some light on dominant reaction pathway and surface carbon formation, which could provide new mechanistic insight into CO 2 reforming methane on Ni-core/Pt-shell surface. [ABSTRACT FROM AUTHOR]

Abstract: Core–shell structured ZnO/In2O3 composites were successfully synthesized via situ growth method. Phase structure, morphology, microstructure and property of the products were investigated by X-ray diffraction (XRD), TG-DTA, field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), transmission electron microscope (TEM) and photoluminescence (PL). Results show that the core–shell structures consist of spindle-like ZnO with about 800nm in length and 200nm in diameter, and In2O3 particles with a diameter of 50nm coated on the surface of ZnO uniformly. HMTA plays an important role in the formation of core–shell structures and the addition of In2O3 has a great effect on PL spectrum. Possible mechanism for the formation of core–shell structures is also proposed in this paper. [Copyright &y& Elsevier]

TEM image of 3D pomegranate-like core@shell porous carbon structure and their comparison figure with the previous reported capacitance values of porous carbon materials. • A functionalized N and O co-doped three-dimensional hierarchical pomegranate-like porous carbon was rationally synthesized. • The hierarchical porous structure, high packing density and enriched N and O functional groups are crucial. • The symmetric suporcapacitor with the pomegranate-like porous carbon boots a high gravimetric (volumetric) energy density. Recently, the heteroatom-enriched porous carbons have received considerable attention on the research of electrodes with high gravimetric capacitances for supercapacitors (SCs). However, their relatively low volumetric capacitances have limited their practical applications due to very low packing density and poor ion diffusion at high mass loadings. In this study, by means of a facile modified chemical activation route, a functionalized N and O co-doped three-dimensional (3D) hierarchical pomegranate-like porous carbon (PPC) was rationally synthesized. First, A core–shell structured precursor composite for PPC was constructed. The polypyrrole (PPy) with the desired functional group was adopted as the precursor of the pomegranate-like core, and the polyacrylamide (PAM) hydrogel as the precursor of the pomegranate-like shell (designated as PPy/PAM). Then, after calcination of the PPy/PAM hydrogel precursor composites, a novel 3D hierarchical PPC was achieved. The as-obtained PPC offers short diffusion paths of ions, increases packing density and provides abundant active sites for pseudocapacitance by increasing self-oxygen–nitrogen-doped content. The performance tests of SC with PPC manifest that at 156 W kg−1 (109.7 W L-1), boosted energy density of 11.5 Wh kg−1 (8.05 Wh L-1) can be achieved. The as-obtained PPC is the promising electrode material of high-performance SCs for practical applications. [ABSTRACT FROM AUTHOR]

• Ag/ND/g-C 3 N 4 photocatalyst was synthesized for the first time. • Ag/ND/g-C 3 N 4 showed enhanced photocatalytic activity both in H 2 evolution from water splitting and degradation of organic pollution. • The Ag/ND/g-C 3 N 4 exhibited good photostability after four-run test. • The photocatalytic reaction mechanism was illustrated in detail. Efficient separation of photogenerated carriers and light harvesting are the two key factors for high photocatalytic performance. In this work, a novel double-heterojunction silver/nanodiamond/graphite-carbon nitride (Ag/ND/g-C 3 N 4) structured photocatalyst has been synthesized. In comparison to single-heterojunction Ag/g-C 3 N 4 , the double-heterojunction Ag/ND/g-C 3 N 4 photocatalyst presents with a 4.9-times enhancement in H 2 evolution from water splitting and 2.4-times promotion in degrading organic pollution under visible-light irradiation. Furthermore, the Ag/ND/g-C 3 N 4 exhibits good photostability after four-run test. The enhanced photocatalytic activity can be attributed to the synergetic effect of surface plasmon resonance from Ag, optical confinement from ND and suitable band alignment in the double-heterojunction structure, which boost the light absorption capacity and increase the photogenerated charge separation of g-C 3 N 4. This study provides a reference for the development of efficient carbon based photocatalysts, which can be used not only for the production of H 2 from water splitting, but also for the photodegradation of pollutants under visible light irradiation. [ABSTRACT FROM AUTHOR]

• The reaction mechanisms of each step evolve with the surface Cl/Cu ratios. • The origin of the K effect was explored by Van-der-Waals corrected DFT calculations. • Free energy analysis is consistent with the experimental observation. • KCl modifies the electronic structure of the surface. Potassium promoters are widely used in industrial catalysts of ethylene oxychlorination to achieve optimum performance. However, the origin of the promoter effect is not fully understood. Herein, we investigated the potassium promotion effect on CuCl 2 /γ-Al 2 O 3 catalyzed ethylene oxychlorination by kinetic experiments and DFT calculations. Kinetic experiments observed the effect of KCl on individual steps, and the evolution of the reaction mechanisms with Cl/Cu ratios. Further exploration via DFT found that KCl increases the formation energy of Cl vacancy (Δ E v) and thus inhibits the reduction activity, which is attributed to the shift-down of Bader charge of Cl. Δ E v boosts with the decline of Cl/Cu ratios; thus, ethylene can extract Cl atoms from the surface with a Cl/Cu ratio of 2, while it anchors to metal atoms at lower Cl/Cu ratios. The distinct adsorption modes reflect the evolution of reaction mechanisms with Cl/Cu ratios. KCl facilitates the adsorption of oxygen owing to the shift-up of the Bader charge of Cu atom. Potassium reduces the Gibbs free energy barrier of the oxidation step, which agrees with the experimental observation. It is concluded that the potassium promoter effect on the catalytic performance mainly results from the modification of the charge of surface atoms. [ABSTRACT FROM AUTHOR]