Zhi-Jun Zuo

Facile preparation of electroactive amorphous α-ZrP/PANI hybrid film for potential-triggered adsorption of Pb2+ ions

An electroactive hybrid film composed of amorphous α-zirconium phosphate and polyaniline (α-ZrP/PANI) is controllably synthesized on carbon nanotubes (CNTs) modified Au electrodes in aqueous solution by cyclic voltammetry method. Electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM) and X-ray power diffraction (XRD) analysis are applied for the evaluation of the synthesis process. It is found that the exfoliated amorphous α-ZrP nanosheets are well dispersed in PANI and the hydrolysis of α-ZrP is successfully suppressed by controlling the exfoliation temperature and adding appropriate supporting electrolyte. The insertion/release of heavy metals into/from the film is reversibly controlled by a potential-triggered mechanism. Herein, α-ZrP, a weak solid acid, can provide an acidic micro-environment for PANI to promote the electroactivity in neutral aqueous solutions. Especially, the hybrid film shows excellent potential-triggered adsorption of Pb(2+) ion due to the selective complexation of Pb(2+) ion with oxygen derived from P-O-H of α-ZrP. Also, it shows long-term cycle stability and rapid potential-responsive adsorption/desorption rate. This kind of novel hybrid film is expected to be a promising potential-triggered ESIX material for separation and recovery of heavy metal ions from wastewater.

Highly-efficient steam reforming of methanol over copper modified molybdenum carbide

Cu doped molybdenum carbide (Cu–MoxCy) catalysts were prepared by carburization of Cu doped molybdenum oxide (Cu–MoO3) using a temperature-programmed reaction with a 20% CH4–H2 mixture at 700 °C. Phase transition of the prepared molybdenum carbide was found to be related to the doping amount of Cu: with the increase in the doping amount of Cu/Mo molar ratio of 1.6/98.4 to 10/90, the cubic α-MoC1−x phase increased in the catalyst, but with the continued increase of the doping amount to a Cu/Mo molar ratio of 15/85, the α-MoC1−x phase began to decrease, and when the Cu doping amount reached a Cu/Mo molar ratio of 25/75, the α-MoC1−x phase became very weak and mainly hexagonal β-Mo2C phase was found in the catalysts. TEM images indicated that carbon growth on the surface of Cu occurred during the carburization process in the case of high Cu doping. Steam reforming of methanol (SRM) over the Cu–MoxCy catalyst was investigated at a temperature range of 200–400 °C. It is found that Cu–MoxCy catalyst with Cu/Mo molar ratios in the range of 1.6/98.4–10/90 showed high catalytic activity as well as long-term stability. X-ray photoelectron spectroscopy analysis indicated the coexistence of CuI and CuII species on the surface of the molybdenum carbide. The existence of CuI could result in high activity for methanol conversion and high stability, which might result from the strong interaction between Cu and Mo2C support.

Low-Temperature Conversion of Methane to Methanol on CeOx/Cu2O Catalysts: Water Controlled Activation of the C–H Bond

An inverse CeO2/Cu2O/Cu(111) catalyst is able to activate methane at room temperature producing C, CHx fragments and COx species on the oxide surface. The addition of water to the system leads to a drastic change in the selectivity of methane activation yielding only adsorbed CHx fragments. At a temperature of 450 K, in the presence of water, a CH4 → CH3OH catalytic transformation occurs with a high selectivity. OH groups formed by the dissociation of water saturate the catalyst surface, removing sites that could decompose CHx fragments, and generating centers on which methane can directly interact to yield methanol.

Embedded structure catalyst: a new perspective from noble metal supported on molybdenum carbide

An embedded structure of noble metal (Pt) in situ supported on molybdenum carbide was found for the first time, which hindered Pt sintering at high temperature, and promoted the interaction between Pt and molybdenum carbide. This structure exhibited an excellent and stable catalytic activity for water gas shift reaction at low temperature.

Facile fabrication of CuO microcube@Fe–Co3O4 nanosheet array as a high-performance electrocatalyst for the oxygen evolution reaction

A “top-down” tactic was offered to synthesize highly efficient electrocatalysts for the oxygen evolution reaction (OER), in which a CuO microcube supported Fe doped Co3O4 nanosheet composite was obtained using a facile unipolar pulse electrodeposition (UPED) method combined with a thermal treatment method. Specifically, an Fe doped Co(OH)2 shell was electrodeposited on the electrode with a Cu particle core simultaneously. Interestingly, it is found that Fe–Co(OH)2 nanosheets grew around the Cu particle core. As a result, a novel electrocatalyst with the Cu cube core and the Fe–Co(OH)2 nanosheet shell was successfully formed in one step. After subsequent thermal oxidation treatment, the CuO microcube@Fe–Co3O4 nanosheet core–shell composite was obtained on the electrode. Benefiting from the one-step electrodeposition, the composite electrode with a smart 3D hierarchical structure as well as the intrinsic activity of Fe–Co3O4 nanosheets showed a remarkably enhanced catalytic performance for OER, which revealed a low overpotential of 232 mV at 10 mA cm−2 current density.

Highly active Au/δ-MoC and Au/β-Mo2C catalysts for the low-temperature water gas shift reaction: effects of the carbide metal/carbon ratio on the catalyst performance

The water gas shift (WGS) reaction catalyzed by orthorhombic β-Mo2C and cubic δ-MoC surfaces with and without Au clusters supported thereon has been studied by means of a combination of sophisticated experiments and state-of-the-art computational modeling. Experiments evidence the importance of the metal/carbon ratio on the performance of these systems, where Au/δ-MoC is presented as a suitable catalyst for WGS at low temperatures owing to its high activity, selectivity (only CO2 and H2 are detected), and stability (oxycarbides are not observed). Periodic density functional theory-based calculations show that the supported Au clusters and the Au/δ-MoC interface do not take part directly in water dissociation but their presence is crucial to switch the reaction mechanism, drastically decreasing the effect of the reverse WGS reaction and favoring the WGS products desorption, thus leading to an increase in CO2 and H2 production. The present results clearly display the importance of the Mo/C ratio and the synergy with the admetal clusters in tuning the activity and selectivity of the carbide substrate.

Theoretical study on the influence of a secondary metal on the Cu(110) surface in the presence of H2O for methanol decomposition

Density functional theory calculations with the continuum solvation slab model are performed to investigate the effect of metal dopants on the Cu(110) surface in the presence of H2O for the methanol decomposition. The sequential dehydrogenation of methanol (CH3OH → CH3O → CH2O → CHO → CO) is studied in the present work. The results show that the introduction of different metals (Pt, Pd, Ni, Mn) on the H2O/Cu(110) surface notably influence the adsorption configurations and adsorption energies of all adsorbates, and remarkably affect the reaction energies and activation energies of the elementary steps. The Pt, Pd and Ni doped H2O/Cu(110) surfaces are able to promote hydrogen production from methanol decomposition, but Mn doped H2O/Cu(110) surfaces are unfavorable for the reaction. The activity of methanol decomposition decreases as follows: Pd–H2O/Cu(110) > Pt–H2O/Cu(110) > Ni–H2O/Cu(110) > H2O/Cu(110) > Mn–H2O/Cu(110). Finally, the Bronsted–Evans–Polanyi plot for the main methanol dissociation steps on the metal doped and un-doped H2O/Cu(110) surfaces are identified, and a linear relationship between the reaction energies and transition state energies is obtained.

Theoretical investigation of H2S removal on γ-Al2O3 surfaces of different hydroxyl coverage

The sulfurized processes of H2S on dehydrated (100) and (110) as well as partially hydrated (110) surfaces of γ-Al2O3 were investigated using a periodic density functional theory method. The adsorption configurations of possible intermediates and the potential energy profiles of reaction are depicted. Our results show that H2S adsorbs preferentially on the Al site along with the S bond, and the adsorption energies are −32.52 and −114.38 kJ mol−1 on the dehydrated (100) and (110) surfaces, respectively. As the reaction temperature of the desulfurization changes, the (110) surface presents different levels of hydroxyl coverage, which affects the adsorption structures of species and reaction energies of dissociation processes. The bonding strengths of H2S on the partially hydrated (110) surfaces are weaker than on the dehydrated (110) surface. Compared with the 3.0 and 8.9 OH per nm2 surfaces, the H2S has the weakest adsorption energy (−39.85 kJ mol−1) and the highest activation energy (92.06 kJ mol−1) on the 5.9 OH per nm2 surface. On the 8.9 OH per nm2 surface, the activation energy of the second dissociation step (rate-determining step) for H2S dissociation is merely 38.32 kJ mol−1. On these involved surfaces, cleavage processes of the two H–S bonds present facile activation energies, which are facilitative to desulfurization.

Ethanol Synthesis from Syngas Over CuZnX (X = Ti, Si, Al, Mg) Catalysts

The catalytic performance of ethanol synthesis from CO hydrogenation over CuZnX (X = Ti, Si, Al, Mg) catalysts prepared by complete liquid phase method are studied. Among these catalysts, CuZnTi catalyst has the best ethanol selectivity about 46.6%. Characterization results show that the interaction between Cu species and metal oxides is a key factor for ethanol synthesis from syngas, which is in accordance with our previous results. CuZnTi catalyst also has good repetitive performance.Graphical Abstract

A DFT study of the catalytic pyrolysis of benzaldehyde on ZnO, γ-Al2O3, and CaO models

AbstractThe catalytic pyrolysis pathways of carbonyl compounds in coal were systematically studied using density functional theory (DFT), with benzaldehyde (C6H5CHO) employed as a coal-based model compound and ZnO, γ-Al2O3, and CaO as catalysts. The results show that the products of both pyrolysis and catalytic pyrolysis are C6H6 and CO. However, the presence of any of the catalysts changes the reaction pathway and reduces the energy barrier, indicating that these catalysts promote C6H5CHO decomposition. Graphical abstractThe presence of catalysts changes the reaction pathway and the energy barrier decreases in the order Ea (no catalyst)> Ea (CaO)> Ea (γ-Al2O3)> Ea (ZnO), indicating that these catalysts promote C6H5CHO decomposition.