Defect-Confinement Strategy for Constructing CuO Clusters on Carbon Nanotubes for Catalytic Oxidation of AsH3 at Room Temperature.

The efficient removal of the highly toxic arsine gas (AsH3) from industrial tail gases under mild conditions remains a formidable challenge. In this study, we utilized the confinement effect of defective carbon nanotubes to fabricate a CuO cluster catalyst (CuO/ACNT), which exhibited a capacity much higher than that of CuO supported on pristine multiwalled carbon nanotubes (MWCNT) (CuO/PCNT) for catalytically oxidizing AsH3 under ambient conditions. The experimental and theoretical results show that nitric acid steam treatment could induce MWCNT surface structural defects, which facilitated more stable anchoring of CuO and then improved the oxygen activation ability, therefore leading to excellent catalytic performance. Density functional theory (DFT) calculations revealed that the catalytic oxidation of AsH3 proceeded through stepwise dehydrogenation and subsequent recombination with oxygen to form As2O3 as the final product.

Enhanced Desulfurization by Tannin Extract Absorption Assisted by Binuclear Sulfonated Phthalocyanine Cobalt Polymer: Performance and Mechanism.

Removal of hydrogen sulfide (H2S) from coke oven gas has attracted increasing attention due to economic and environmental concerns. In this study, tannin extract (TE) absorption combined with binuclear sulfonated phthalocyanine cobalt organic polymer (OTS) and binuclear sulfonated phthalocyanine cobalt (PDS) with a fixed bed reactor is used for removal of H2S. The effect of gas flow rate, concentration of H2S, co-existence of organic sulfide compounds and O2 were investigated. Then, the effect of total alkalinity content of TE, NaVO3, OTS and PDS was studied in detail. The experimental results demonstrated that 100% H2S conversion could maintain for 13 h at a total alkalinity of 5.0 g/L, TE concentration of 4.0 g/L, NaVO3 concentration of 5 g/L, and OTS and PDS concentration of 0.2 g/L and 0.2 g/L, respectively. The OTS and PDS showed synergistic effect on boosting TE desulfurization efficiency. The results provide a new route for the investigation of liquid catalyzed oxidation desulfurization in an efficient and low-cost way.

Catalytic oxidation mechanism of AsH3 over CuO@SiO2 core-shell catalysts via experimental and theoretical studies.

In this study, CuO@SiO2 core-shell catalysts were successfully synthesized and applied to efficiently remove hazardous gaseous pollutant arsine (AsH3) by catalytic oxidation under low-temperature and low-oxygen conditions for the first time. In typical experiments, the CuO@SiO2 catalysts showed excellent AsH3 removal activity and stability under low-temperature and low-oxygen conditions. The duration of the AsH3 conversion rate above 90 % for the CuO@SiO2 catalysts was 39 h, which was markedly higher than that of other catalysts previously reported in the literature. The considerable catalytic activity and stability were attributed to the protection and confinement effects of the SiO2 shell, which resulted in highly dispersed CuO nanoparticles. Meanwhile, the strong interaction between the CuO core and SiO2 shell further facilitated the formation of active species such as coordinatively unsaturated Cu2+ and chemisorbed oxygen. The accumulation of oxidation products (As2O3 and As2O5) on the interface between the CuO core and SiO2 shell and the pore channels of the SiO2 shell is the main cause of catalysts deactivation. Furthermore, through combined density functional theory (DFT) calculations and characterization methods, a reaction pathway including gradual dehydrogenation (AsH3*→AsH2*→AsH*→As*) and gradual oxidation (2As*→As*+AsO*→2AsO*→As2O3) for the catalytic oxidation of AsH3 on CuO (111) surface was constructed to clarify the detailed reaction mechanism. The CuO@SiO2 core-shell catalysts applied in this study could provide a powerful method for developing AsH3 catalysts from multiple know AsH3 removal systems.

Experimental and theoretical studies on NO selective catalytic oxidation over α-MnO2.

Based on the experimental and theoretical methods, the NO selective catalytic oxidation process was proposed. The experimental results indicated that lattice oxygen was the active site for NO oxide over the α-MnO2(110) surface. In the theoretical study, DFT (density functional theory) and periodic slab modeling were performed on an α-MnO2(110) surface, and two possible NO oxidation mechanisms over the surface were proposed. The non-defect α-MnO2(110) surface showed the highest stability, and the surface Os (the second layer oxygen atoms) position was the most active and stable site. O2 molecule enhanced the joint adsorption process of two NO molecules. The reaction process, including O2 dissociation and O=N-O-O-N=O formation, was calculated to carry out the NO catalytic oxidation mechanism over α-MnO2(110). The results showed that NO oxidation over the α-MnO2(110) surface exhibited the greatest possibility following the route of O=N-O-O-N=O formation. Meanwhile, the formation of O=N-O-O-N=O was the rate-determining step.

Plasma-Assisted Reforming of Methane.

Methane (CH4 ) is inexpensive, high in heating value, relatively low in carbon footprint compared to coal, and thus a promising energy resource. However, the locations of natural gas production sites are typically far from industrial areas. Therefore, transportation is needed, which could considerably increase the sale price of natural gas. Thus, the development of distributed, clean, affordable processes for the efficient conversion of CH4 has increasingly attracted people's attention. Among them are plasma technology with the advantages of mild operating conditions, low space need, and quick generation of energetic and chemically active species, which allows the reaction to occur far from the thermodynamic equilibrium and at a reasonable cost. Significant progress in plasma-assisted reforming of methane (PARM) is achieved and reviewed in this paper from the perspectives of reactor development, thermal and nonthermal PARM routes, and catalysis. The factors affecting the conversion of reactants and the selectivity of products are studied. The findings from the past works and the insight into the existing challenges in this work should benefit the further development of reactors, high-performance catalysts, and PARM routes.

First-principles studies of HF and HCl adsorption over graphene.

In this paper, the adsorption characteristics of HF and HCl over graphene were studied by the first-principles method. The results showed that the adsorption of HCl over graphene was a weak chemical adsorption, while HF was a weak physical adsorption. The density of states showed that HCl and graphene at - 4.3 eV are relative to the Fermi level. At the same time, there is no obvious change and hybridization between HF-graphene system near the Fermi level. Furthermore, when HCl and HF molecules adsorbed over the graphene simultaneously, two optimal adsorption structures would be chosen to investigate how HCl and HF molecules jointly affected adsorption properties. The result showed that two gas molecules adsorbed over graphene could enhance the adsorption effect and influenced electronic distribution. Graphical abstract HF and HCl over graphene belong to weak physical and chemical adsorption separately. Two gases on graphene surface can be enhanced.

Theoretical study on NO x adsorption properties over the α-MnO2(110) surface.

Herein, α-MnO2 was studied as an adsorbent for the removal of NO x (NO, NO2) derived from flue gas. First-principles calculations based on the density functional theory (DFT) were performed to investigate the NO x adsorption properties over the α-MnO2(110) surface. NO strongly adsorbed over the α-MnO2(110) surface via chemisorption spontaneously under 550 K. The NO2 molecules adsorbed over the surface via chemisorption and physisorption when the terminal N- and O atoms approached the surface, respectively. The joint adsorption of NO x was more stable than the isolated adsorption system. Furthermore, the net charge was transferred from the molecule to the surface. The surface and temperature affected the entropy, enthalpy, NO adsorption and NO2 desorption in the temperature range of 300-550 K. The equilibrium constants decreased with an increase in temperature, which reduced the conversion rate.

Theoretical study on simultaneous removal of SO2, NO, and Hg0 over graphene: competitive adsorption and adsorption type change.

In this work, the influence of competitive adsorption and the change of charge transfer for simultaneous adsorption removal of SO2, NO, and Hg0 over graphene were investigated using density functional theory method. The results showed that all the adsorptive effect of SO2, NO, and Hg0 were caused by physical interaction. The adsorptive energy of SO2 was the highest, and the adsorptive energy of Hg0 was the lowest. SO2 could be preferentially adsorbed and removed. NO/SO2 and Hg0 had the mutual promotion effect for simultaneous adsorption over graphene surface. SO2 and NO had the mutual inhibition effect for simultaneous adsorption over graphene surface. Compared with single molecular adsorption, the adsorption type of bi-molecular adsorption did not change. However, the simultaneous adsorption changed the adsorption type of Hg0 + SO2 + NO to chemical adsorption due to the interaction among Hg0, SO2, and NO. As such, this study provides a theoretical insight for future application and development. Graphical abstractNO/SO2 and Hg0 had the mutual promotion effect for simultaneous adsorption. SO2 and NO had the mutual inhibition effect for simultaneous adsorption.