Abstract: In this work, a Fe-doped Co3O4 OER electrocatalyst supported by an N-doped hollow nanocage carbon framework (Fe-Co3O4/NC) was successfully prepared by anion exchange and annealing in an air atmosphere strategy. XRD and HRTEM characterizations confirm that Fe the incorporation of Fe into the lattice of Co3O4. XPS characterization clarifies that the valence state of Co increases after the introduction of Fe, which originates from the electrons transfer from Co2+/Co3+ to Fe3+ and is induced by the valence electron configuration of cations. It simulates Co sites in-situ derived into CoOOH active species during the OER process, which is confirmed by the HRTEM and XPS characterization after the OER stability test. Electrochemical performance tests show that the Fe-Co3O4/NC electrocatalyst only exhibits 275 mV overpotential to achieve a current density of 10 mA/cm2 and stably maintains for 20 h at 100 mA/cm2. Together with 20% Pt/C electrocatalyst, the composed two-electrode system only needs 2.041 V applied potential to achieve 100 mA/cm2 for total water splitting in a self-made membrane electrode device, which has industrial application prospects.
Abstract: We anchored atomically dispersed Fe-N4 sites on hollow N-doped carbon spheres (Fe SAs/HNCSs-800) for electrocatalytic ORR; the obtained material exhibited electrocatalytic activity and stability comparable to that of commercial Pt/C, with an onset potential of 0.925 V and a half-wave potential of 0.867 V. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectroscopy results confirmed the presence of highly dispersed Fe single atoms in Fe SAs/HNCSs-800. The results of experiments and theoretical calculations show that the single-atom dispersed Fe-N4 serve as the ORR active sites, and the adjacent C defects can effectively regulate the electronic structure of Fe atoms and improve the electrocatalytic ORR activity.
Abstract: Comparing the composite TiO2 prepared by hydrothermal sol gel method and microwave-assisted sol gel method, the microwave-assisted sol gel method with shorter time and better crystallinity was finally used to prepare ZnO-TiO2 materials with different composite ratios. The specific surface area, pore volume and pore size of ZnO- TiO2 composite are significantly larger than those of TiO2. The surface acidity of ZnO-TiO2 composite is stronger. The band structure is conducive to the efficient separation of electrons and holes, and the catalytic reduction activity and selectivity are stronger. The best composite ratio of ZnO and TiO2 is optimized to be 0.2 through photocatalytic denitration experiments. For NOx with an initial concentration of 6.83 mg/m3, under the light source condition irradiated by 65 W energy-saving lamp, the visible photocatalytic removal efficiency is as high as 85%. When the NOx concentration is increased to 13.67 mg/m3 and the ammonia nitrogen ratio is 1∶1, the denitration efficiency is as high as 96%, which is 43% higher than that of pure TiO2. According to mechanism analysis, the whole reaction can be divided into adsorption and photocatalysis. Adsorption is the speed control step of the reaction. NO is oxidized to NO2 under the action of adsorbed oxygen, and photogenerated electrons can further reduce NO2 to N2. After NH3 is introduced, NH3 and photogenerated electrons work together to improve NOx removal efficiency.
Abstract: In this work, to better understand catalytic gasification process of direct coal liquefaction residue rich in sodium species, char structure evolution and behaviors of sodium species during gasification under CO2 atmosphere were investigated in detail by N2 adsorption and desorption, FT-IR, XRD, SEM, and Raman analyses. The results show that sodium species developed pore structure of direct coal liquefaction residue during gasification, especially expanded mesoporous structures which increased from 0.05 to 0.16 cm3/g at maximum. With the increase of gasification time, different crystalline compounds were formed in chars. Most of the mineral matters identified by XRD were calcium-containing ones, whereas no obvious sodium-containing crystalline compounds were found. This was because that most of sodium species volatilized at high temperature and the crystalline forms of sodium-containing compounds had defects. Compared with sodium species, calcium species were more prone to react with aluminosilicates, which happened to make sodium species remain active during gasification process. The ratio of (GR + VL + VR)/D rose initially and then decreased, which could be explained as the dissociation of the large aromatic and the rearrangement of small aromatic rings into large aromatic structures. Moreover, release ratio of sodium species was closely related with gasification time and 49.8% of them released in the initial stage of gasification process (within 15 min). Compared with that of direct coal liquefaction residue reloaded with water-soluble sodium species, the release ratio of sodium species in the original direct coal liquefaction residue was on a lower level (85.2% versus 89.7%).
Abstract: A series of silicon spheres supported cobalt catalysts were prepared by incipient wetness impregnation followed by decomposition under treatment of glow discharge plasma with different intensities. The catalysts were characterized by X-ray powder diffraction, N2 physical adsorption-desorption, H2 temperature-programmed reduction, transmission electron microscope and Fourier-Transform Infrared spectroscopy. The Fischer-Tropsch synthesis performance were tested on a fixed bed reactor. The influence of plasma treatment on cobalt dispersion, reducibility and cobalt-support interaction were analyzed and discussed. The results showed that the plasma-treated catalysts had better catalytic performance than the calcined sample. The Co/SP-P650W catalyst showed the highest reaction activity due to the proper cobalt dispersion and higher cobalt reducibility.
Abstract: In the present study, the kinetic behaviour and active sites evolution processes of Pt-based catalysts were investigated. It was found that highly selective hydrogen combustion could be achieved over Sn modified Pt-based catalysts in presence of both propane and propene (over 98%). The stability tests, kinetic study and catalyst characterization revealed that the existence of oxygenated species is the reason for accelerated coking reactions. The formation of graphitized cokes serving as additional unselective active sites and the oxidation of tin in PtSn alloy phases are the primary reasons causing the catalytic selectivity loss during long-run tests under propene-rich condition.
Abstract: Zeolites have been extensively used in the chemical and petrochemical industries owing to their tunable acidities and unique pore structures. Beta zeolite with Brönsted and Lewis acids and AlCl3@Si-Beta with only Lewis acid were prepared by hydrothermal synthesis and gas-phase impregnation methods, respectively. Mechanisms differences of Brönsted and Lewis acids on four pentene isomers transformation were investigated by in situ diffraction infrared Fourier transform spectrum (DRIFTS). The results suggested that Brönsted in Beta played a main role in isomerization and oligomerization reactions which all followed classical carbenium ion mechanisms. On the contrary, Lewis acid in AlCl3@Si-Beta without hydrogen proton or hydroxyl catalyzed α-pentene double-bond migration to produce β-pentene and cis-trans isomerization reaction of 2-pentene by AB-AD mechanism with allyl-like species as intermediates, and could not catalyze pentenes skeletal isomerization and oligomerization reactions.
Abstract: Polyethylnaphthalenes lubricating base oil were synthesized by alkylation of cooking naphthalene with ethylene using organic ammonium salt/metal chloride ionic liquid as catalyst. It was found that the AlCl3/Et3NHCl ionic liquid showed better active in the naphthalene alkylation with ethylene by regulating the composition of anions and cations in ionic liquids. Two different compositions of polyethylnaphthalenes base oils PEN-1 (92.9% of mono- and di-ethylnaphthalenes) and PEN-2 (91.3% of polyethylnaphthalenes) were synthesized by optimizing reaction conditions (catalyst dosage, reaction time and temperature). The lubrication test results showed that PEN-2 base oil with a large number of alkyl side chains exhibited good tribological properties and showed better wear resistance than the commercial alkylnaphthalenes base oil AN5, showing a good application prospect.
Abstract: La2O3 catalysts with different grain sizes were prepared under hydrothermal condition. The structure activity relationship of La2O3 catalysts with different grain sizes were investigated by using in-situ XRD, Raman, FT-IR and H2-TPR, O2-TPD. The results showed that the La−O bond of the La2O3 catalyst showed a significant elongation with increasing temperature, which affected its adsorption and dynamic storage of O2. When increasing the grain size up to 57.4 nm, the oxygen storage capacity of the La2O3 catalyst started to decrease, accompanied by the enrichment of surface oxygen species, especially superoxide species, on the catalyst surface, which led to the over-oxidation of CH4 and products and reduced the C2 + hydrocarbons selectivity. The L-La2O3 catalyst with a grain size of 52.3 nm had a suitable content of surface oxygen species and a high oxygen storage capacity at 750 ℃. It exhibited the best C2 + hydrocarbon selectivity up to a CH4/O2 of 3 and a vacancy rate of 1.6 × 105 mL/(g·h).
Abstract: Direct synthesis of liquefied petroleum gas from syngas via Fischer-Tropsch synthesis route was systematically investigated over a nano-level core@shell catalyst. We introduced an incorporation of FeMg catalyst into mesoporous silica shell, with a further modification of Cu particles on the silica surface. The modified Cu/FeMg@SiO2 nano core-shell catalysts were synthesized by the combination of co-precipitation, modified sol-gel and facile impregnation methods. The as-synthesized catalysts’ physicochemical property was characterized by XRD, TEM, N2 adsorption-desorption, H2-TPR, XPS and CO2-TPD techniques. The catalytic performance of Cu/FeMg@SiO2 catalyst shows a high CO conversion of 96.6%, rather low CO2 selectivity of 21.9% and considerable LPG selectivity of 37.9%. The catalytic results indicate that the SiO2 shell restrains the formation of CH4 and contributes to increasing long-chain products. Meanwhile, the enhanced CO conversion of Cu/FeMg@SiO2 was ascribed to the active metal Cu dispersed on SiO2 shell, which also promoted olefin hydrogenation and cracking of C5+ hydrocarbons products. The proposed catalyst preparation method will provide a new strategy for the synthesis of nano level catalyst with combinations of metal- and zeolite-based catalyst.
Abstract: Using pseudo-boehmite and ultrafine copper hydroxide as the raw materials with n(Cu/Al) = 1∶3, the effects of ball milling medium on the Cu-Al spinel sustained release catalysts prepared via the solid-state reaction method are explored. The obtained catalysts are characterized by XRD, BET, and H2-TPR techniques, and their catalytic properties in methanol steam reforming (MSR) are evaluated. The results demonstrate that Cu-Al spinel solid solution can be synthesized by both dry and wet mechanical ball milling methods, and more Cu2 + ions are found to be incorporated into the spinel lattice through the latter method. The crystalline sizes of as-synthesized spinels are similar; however, the specific surface areas and pore volumes are different as well as their reduction properties. Compared with the dry milling method, the wet ball milling method can facilitate the solid phase reaction, generating catalysts with solely spinel crystalline phase, higher specific surface area, and larger pore volume. Furthermore, catalysts derived from the wet milling method demonstrate improved catalytic activity and stability, and lower CO selectivity in MSR. The highest activity is obtained over CuHAl-Ac-950 prepared using ethanol (95%) as the ball milling medium.
Abstract: La2O3 as a catalyst is used for oxidative coupling of methane (OCM) reactions due to its excellent stability and high C2 selectivity, but poor activity on methane dissociation limits its wide application. Different valence metals are doped on the La2O3(001) surface to improve the methane conversion activity, and the activation of methane on metal-doped La2O3(001) surfaces has been investigated via the density functional theory (DFT) calculations. The relationship between the valence states of doped metals and the methane conversion activities shows that doping low valence metals (Li, Na, K, Mg, Ca, Sr and Ba) and equivalent metals (Al, Ga, In) can significantly improve the conversion activity of methane. Among them, the activation energy of methane on the Li-La2O3(001) surface is the lowest, which is only 13.0 kJ/mol. However, doping of high valence metals (Zr, Nb, Re and W) cannot improve the CH4 dissociation activity. Furthermore, the relationships between surface oxygen vacancy formation energies, acid-base properties and the activation energies of CH4 have also been investigated. The results show that with the increase of metal valence state, the oxygen vacancy formation energy increases, while the dissociation activity of CH4 decreases. The introduction of alkali and alkaline earth metals increases the alkalinity of La2O3(001) surface, and the alkalinity of La2O3(001) doped with the alkali metal is stronger than that with the alkaline earth metal, exhibiting higher dissociation activity of CH4. Our research may provide a guide for improving methane conversion activity on La2O3 catalysts.
Abstract: As the most promising hydrogen storage material, hydrous hydrazine (N2H4·H2O) has attracted extensive attention and interest of researchers. In this paper, NiPt bimetallic supported SBA-15 (mesoporous silica) catalysts with different metal ratios were prepared by a simple impregnation reduction method, and their catalytic hydrous hydrazine dehydrogenation performance was studied. The research results show that Pt and Ni form an alloy during the preparation of the catalyst, the electronic synergistic effect of the two metals can effectively promote the catalytic performance of the catalyst, and the interaction between SBA-15 and the metal active components helps to improve the catalytic performance and cycling stability of catalysts. The activation energy of the Pt6Ni4/SBA-15 catalyst is 45.6 kJ/mol and the TOF value is 2123.3 h−1, which are better than most of the reported catalysts.
Abstract: The lack of high performance and low cost oxygen reduction electrocatalysts, especially operating in the wide pH range, is one of the key obstacles restricting the large-scale applications of new energy conversion technologies such as fuel cells and metal-air batteries. In this work, based on the synthesis mechanism of conventional polymer-derived carbon materials, a bimetallic oxy-nitride (ComTinOxNy)-Co single atom (Co-NC) composite catalyst was prepared by an associated hydrothermal polymerization-pyrolysis method through selecting suitable precursor molecules and simultaneously introducing TiO2 nanoparticle in the process of polymerization. The bimetallic cobalt-titanium oxy-nitride Co-NC composite catalyst exhibits better ORR activity in a wide pH range (0−13) than the conresponding pure N-doped carbon nanotubes, titanium oxy-nitride/N-CNTs and Co-NC catalysts, providing a new idea for the development of ORR electrocatalysts with high performance and low cost.
Abstract: Fe/C-based composite microwave absorption (MA) materials were prepared by high temperature solid phase reaction between coal hydrogasification semi-coke (SC for short) and solid waste red mud (RM). In order to optimize MA performance, initial system composition was changed. It was found that, under an argon atmosphere and reaction temperature of 900 ℃, the composites obtained from systems with mass ratio of SC to RM (MRSR) at 0.4∶1−0.7∶1 all showed excellent performance, and that corresponding to MRSR of 0.6∶1 was the best. At a coating thickness of 1.5 mm, the simulated minimum reflection loss and effective absorption bandwidth could reach −48.3 dB and 4.6 GHz, respectively. The strong intrinsic attenuation ability mainly resulted from the dielectric loss due to the presence of graphite carbon as well as a large number of phase boundaries and defects. And the impedance matching between material and free space was attributed to the effective regulation on electromagnetic parameters of the initial system composition. Moreover, the solid phase combination reaction among Na2O, Al2O3 and SiO2 could weaken the strong alkalinity caused by RM.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
