Oxygen-deficient MoOx/Ni3S2 heterostructure grown on nickel foam as efficient and durable self-supported electrocatalysts for hydrogen evolution reaction

High-performance and ultra-durable electrocatalysts are vital for hydrogen evolution reaction (HER) during water splitting. Herein, by one-pot solvothermal method, MoO_x/Ni₃S₂ spheres comprising Ni₃S₂ nanoparticles inside and oxygen-deficient amorphous MoO_x outside in situ grow on Ni foam (NF), to assembly the heterostructure composites of MoO_x/Ni₃S₂/NF. By adjusting volume ratio of the solvents of ethanol to water, the optimized MoO_x/Ni₃S₂/NF-11 exhibits the best HER performance, requiring an extremely low overpotential of 76 mV to achieve the current density of 10 mA∙cm^‒2 (η₁₀ = 76 mV) and an ultra-small Tafel slope of 46 mV∙dec^‒1 in 0.5 mol∙L^‒1 H₂SO₄. More importantly, the catalyst shows prominent high catalytic stability for HER (> 100 h). The acid-resistant MoO_x wraps the inside Ni₃S₂/NF to ensure the high stability of the catalyst under acidic conditions. Density functional theory calculations confirm that the existing oxygen vacancy and MoO_x/Ni₃S₂ heterostructure are both beneficial to the reduced Gibbs free energy of hydrogen adsorption (|∆G_H*|) over Mo sites, which act as main active sites. The heterostructure effectively decreases the formation energy of O vacancy, leading to surface reconstruction of the catalyst, further improving HER performance. The MoO_x/Ni₃S₂/NF is promising to serve as a highly effective and durable electrocatalyst toward HER.     

Characterization and catalytic activity of soft-templated NiO-CeO2 mixed oxides for CO and CO2 co-methanation

Nanosized NiO,CeO₂ and NiO-CeO₂ mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method.All the samples were characterized by different techniques as to their chemical composition,structure,morphology and texture.On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined.NiO and CeO₂ nanocrystals of about 4 nm in size were obtained,regardless of the Ni/Ce molar ratio.The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO₂ interface,where Ni species are in strong interaction with the support.The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that,unlike metallic nickel,CeO₂ is able to effectively adsorb CO₂,forming carbonates and hydrogen carbonates.After reduction in H2 at 400°C for 1 h,the catalytic performance was studied in the CO and CO₂ co-methanation reaction.Catalytic tests were performed at atmospheric pressure and 300°C,using CO/CO₂/H₂ molar compositions of 1/1/7 or 1/1/5,and space velocities equal to 72000 or 450000 cm³?h^-1?gcat^-1.Whereas CO was almost completely hydrogenated in any investigated experimental conditions,CO₂ conversion was strongly affected by both the CO/CO₂/H₂ ratio and the space velocity.The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO₂ methanation.On a selected sample,the influence of the reaction temperature and of a higher number of space velocity values,as well as the stability,were also studied.Provided that the Ni content is optimized,the NiCe system investigated was very promising,being highly active for the CO_x co-methanation reaction in a wide range of operating conditions and stable(up to 50 h)also when submitted to thermal stress.     

The reactions of ethanol over M/CeO2 catalysts: Evidence of carbon–carbon bond dissociation at low temperatures over Rh/CeO2

The reactions of ethanol over Rh/CeO₂ have been investigated using the techniques of temperature programmed desorption (TPD) and FT-IR spectroscopy, in addition to steady state catalytic tests. A comparison with previous studies of ethanol adsorption over Pd/CeO₂ [J. Catal. 186 (1999) 279] and Pt/CeO₂ [J. Catal. 191 (2000) 30] catalysts is presented. The apparent activation energy for the reaction was 49, 40, and 43 kJ mol⁻¹ for Rh/CeO₂, Pd/CeO₂ and Pt/CeO_2, respectively, while the turnover number (TON) at 400 K was 5.9, 8.6 and 2.6, respectively. Surface compositions of catalysts were characterised by XPS. A decrease of the atomic O(1s)/Ce(3d) ratio of the CeO₂ support indicates its partial reduction upon addition of the noble metal. The extent of reduction per metal atom was in the following order: Pt>Pd>Rh. FT-IR and TPD studies have shown that dehydrogenation of ethanol to acetaldehyde occurred over Pd/CeO₂, Pt/CeO₂ and Rh/CeO₂. Moreover, Rh/CeO₂ readily dissociated the C–C bond of ethanol at room temperature to form adsorbed CO (IR bands at 1904–2091 cm⁻¹). This was corroborated by the low desorption temperature of CH₄ over Rh/CeO₂ (450 K) when compared to that of Pd/CeO₂ (550 K) or Pt/CeO₂ (585 K).     

The effect of CeO2 structure on the activity of supported Pd catalysts used for methane steam reforming

Palladium (Pd) supported on CeO₂-promoted γ-Al₂O₃ with various CeO₂ (ceria) crystallinities, were used as catalysts in the methane steam reforming reaction. X-ray diffraction (XRD) analysis, FTIR spectroscopy of adsorbed CO, and X-ray photoelectron spectroscopy (XPS) were employed to characterize the samples in terms of Pd and CeO₂ structure and dispersion on the γ-Al₂O₃ support. These results were correlated with the observed catalytic activity and deactivation process. Arrhenius plots at steady-state conditions are presented as a function of CeO₂ structure. Pd is present on the oxidized CeO₂-promoted catalysts as Pd⁰, Pd⁺ and Pd²⁺, at ratios strongly dependent on CeO₂ structure. XRD measurements indicated that Pd is well dispersed (particles <2 nm) on crystalline CeO₂ and is agglomerated as large clusters (particles in 10–20 nm range) on amorphous CeO₂. FTIR spectra of adsorbed CO revealed that after pre-treatment under H₂ or in the presence of amorphous CeO₂, partial encapsulation of Pd particles occurs. CeO₂ structure influences the CH₄ steam reforming reaction rates. Crystalline CeO₂ and dispersed Pd favor high reaction rates (low activation energy). The presence of CeO₂ as a promoter conferred high catalytic activity to the alumina-supported Pd catalysts. The catalytic activity is significantly lower on Pd/γ-Al₂O₃ or on amorphous (reduced) CeO₂/Al₂O₃ catalysts. The reaction rates are two orders of magnitude higher on Pd/CeO₂/γ-Al₂O₃ than on Pd/γ-Al₂O₃, which is attributed to a catalytic synergism between Pd and CeO₂. The low rates on the reduced Pd/CeO₂/Al₂O₃ catalysts can be correlated with the loss of Pd sites through encapsulation or particle agglomeration, a process found mostly irreversible after catalyst regeneration.     

Tuning porosity of coal-derived activated carbons for CO2 adsorption

A simple method was developed to tune the porosity of coal-derived activated carbons, which provided a model adsorbent system to investigate the volumetric CO₂ adsorption performance. Specifically, the method involved the variation of the activation temperature in a K₂CO₃ induced chemical activation process which could yield activated carbons with defined microporous (< 2 nm, including ultra-microporous < 1 nm) and meso-micro-porous structures. CO₂ adsorption isotherms revealed that the microporous activated carbon has the highest measured CO₂ adsorption capacity (6.0 mmol∙g^–1 at 0 °C and 4.1 mmol∙g^–1 at 25 °C), whilst ultra-microporous activated carbon with a high packing density exhibited the highest normalized capacity with respect to packing volume (1.8 mmol∙cm⁻³ at 0 °C and 1.3 mmol∙cm^–3 at 25 °C), which is significant. Both experimental correlation analysis and molecular dynamics simulation demonstrated that (i) volumetric CO₂ adsorption capacity is directly proportional to the ultra-micropore volume, and (ii) an increase in micropore sizes is beneficial to improve the volumetric capacity, but may lead a low CO₂ adsorption density and thus low pore space utilization efficiency. The adsorption experiments on the activated carbons established the criterion for designing CO₂ adsorbents with high volumetric adsorption capacity.     

On the mechanism of model diesel soot-O2 reaction catalysed by Pt-containing La-doped CeO2: A TAP study with isotopic O2

Pt supported on CeO₂ and 10 wt.% La³⁺-doped CeO₂ catalysts have been prepared, characterised and tested for soot oxidation by O₂ in TGA. The reaction mechanism has been studied in a TAP reactor with labelled O₂. Isotopic oxygen exchange between molecular O₂ and ‘O’ on the support/catalyst was observed and soot oxidation is being carried out by lattice oxygen. TAP studies further show that Pt improves O₂ adsorption and, therefore, 5 wt.% Pt-containing catalysts are more active for soot oxidation than the counterpart supports. In addition, CeO₂ doping by La³⁺ leads to an improved support, since La³⁺ stabilises the structure of CeO₂ when calcined at high temperature (1000 °C) and minimises sintering. In addition, La³⁺ improves the Ce⁴⁺/Ce³⁺ reduction as deduced from H₂-TPR experiments and favours oxygen mobility into the lattice. A synergetic effect of Pt and La³⁺ is observed, Pt-containing La³⁺-doped CeO₂ being the most active catalyst for soot oxidation by O₂ among the samples studied.     

低温等离子体协同CeO2/13X催化降解甲苯

低温等离子体协同催化剂技术（NTP-CAT）由于操作方便、能耗低等特点,特别适合用于工业非连续或连续消除低浓度VOCs过程。本研究发现NTP-CAT体系中CeO₂基催化剂更适合负载于13X载体以降解甲苯,并进一步考察CeO₂负载量对VOCs消除效果的影响。结果发现,NTP-CAT 体系中30% CeO₂/13X表现出最优性能,其可降解约85%的甲苯,CO₂产物选择性可达55%。表征结果也表明,Ce组分在30% CeO₂/13X表面仍可较好分散,而且表面的Ce³⁺物种含量最高。O₂-TPD实验结果证实表面Ce³⁺物种来源于Ce⁴⁺物种的等离子体处理。而且,表面Ce³⁺含量越高,有利于产生更多的氧物种,随后将与其周边13X吸附活化的甲苯反应。因此,甲苯降解在NTP-CAT体系中应存在分工协同机制。     

Efficient MgO-doped CaO sorbent pellets for high temperature CO2 capture

Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation. The effect of Na⁺ and MgO on the structure and CO₂ adsorption performance of CaO sorbent pellets was elucidated. MgO-doped CaO sorbent pellets with the diameter range of 0.5-1.5 mm exhibited an excellent capacity for CO₂ adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents. The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles. The presence of mesopores and macropores resulted in appreciable change of volume from CaO (16.7 cm³∙mol⁻¹) to CaCO₃ (36.9 cm³∙mol⁻¹) over repeated operation cycles. Ca2Mg1 sorbent pellets exhibited favorable CO₂ capture capacity (9.49 mmol∙g⁻¹), average adsorption rate (0.32 mmol∙g⁻¹∙min⁻¹) and conversion rate of CaO (74.83%) after 30 cycles.     

The effect of ceria content on the performance of Pt/CeO2/Al2O3 catalysts in the partial oxidation of methane

The effect of CeO₂ loading (1–20 wt.%) on the properties and catalytic behaviors of CeO₂–Al₂O₃-supported Pt catalysts on the partial oxidation of methane was studied. The catalysts were characterized by S_BET, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and oxygen storage capacity (OSC). XRD and TPR results showed that the pretreatment temperature of the support influences on the amount of CeO₂ with fluorite structure. The pretreatment temperature of the support and CeO₂ loading influenced the morphology of Pt. OSC analysis showed a significant increase in the oxygen storage capacity per weight of CeO₂ for samples with high CeO₂ loading (12 and 20 wt.%). TPR analyses showed that the addition of Pt promotes the reduction of CeO₂. This effect was more significant for the catalysts with high CeO₂ loading (≥12 wt.%). The dispersion of Pt, measured by the rate of cyclohexane dehydrogenation, increases with increasing of the pretreatment temperature of the support. It was shown that the kind of the support is very important for obtaining of catalysts resistant to carbon formation. The catalysts with high CeO₂ loading (≥12 wt.%) showed the highest catalytic activity and stability in the reaction of partial oxidation of methane due to a higher Pt–CeO₂ interface.     

Fe2Mo3O8 nanoparticles self-assembling 3D mesoporous hollow spheres toward superior lithium storage properties

Unique self-assembled iron(II)molybdenum(IV)oxide(Fe₂Mo₃O₈)mesoporous hollow spheres have been facilely constructed via the bubble-template-assisted hydrothermal synthesis method combined with simple calcination.The compact assembly of small nanoparticles on the surface of the hollow spheres not only provides more active sites for the Fe₂Mo₃O₈,but also benefits the stability of the hollow structure,and thus improved the lithium storage properties of Fe2Mo3O8.The Fe₂Mo₃O₈ mesoporous hollow spheres exhibit high initial discharge and charge capacities of 1189 and 997 mA?h?g^?1 respectively,as well as good long-term cycling stability(866 mA?h?g^?1 over 70 cycles)when used as a lithium-ion battery anode.This feasible material synthesis strategy will inspire the variation of structural design in other ternary metal molybdates.     

Electrochemical sensor investigation of carbon-supported PdCoAg multimetal catalysts using sugar-containing beverages

Novel PdCoAg/C nanostructures were successfully synthesized by the polyol method in order to develop electrocatalysts, related to the glucose sensor performance of the high glycemic index in beverages. The characterization of this novel PdCoAg/C electrocatalyst was performed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy equipped with energy dispersive X-ray. The characterization results revealed that electronic state of the PdCoAg/C electrocatalyst was modified by the addition of the third metal. The electrochemical performances of the sensor were investigated by cyclic voltammetry and differential pulse voltammetry. The prepared enzyme-free sensor exhibited excellent catalytic activity against glucose with a wide detection range (0.005 to 0.35 mmol∙L⁻¹), low limit of detection (0.003 mmol∙L⁻¹), high sensitivity (4156.34 µA∙mmol⁻¹∙L∙cm⁻²), and long-term stability (10 days) because of the synergistic effect between the ternary metals. The glucose contents of several energy drinks, fruit juices, and carbonated beverages were analyzed using the novel PdCoAg/NGCE/C sensor system. These results indicate the feasibility for applications in the foods industry.     

Potential rare-earth modified CeO2 catalysts for soot oxidation part II: Characterisation and catalytic activity with NO + O2

Ceria (CeO₂) and rare-earth modified ceria (CeReO_x with Re = La³⁺, Pr^3+/4+, Sm³⁺, Y³⁺) supports and Pt impregnated supports are studied for the soot oxidation under a loose contact with the catalyst with the feed gas, containing NO + O₂. The catalysts are characterised by XRD, H₂-TPR, DRIFT and Raman spectroscopy. Among the single component oxides, CeO₂ is significantly more active compared with the other lanthanide oxides used in this study. Doping CeO₂ with Pr^3+/4+ and La³⁺ improved, however, the soot oxidation activity of the resulting solid solutions. This improvement is correlated with the surface area in the case of CeLaO_x and to the surface area and redox properties of CePrO_x catalyst. The NO conversion to NO₂ over these catalysts is responsible for the soot oxidation activity. If the activity per unit surface area is compared CePrO_x is the most active one. This indicates that though La³⁺ can stabilise the surface area of the catalyst in fact it decreases the soot oxidation activity of Ce⁴⁺. The lattice oxygen participates in NO conversion to NO₂ and the rate of this lattice oxygen transfer is much faster on CePrO_x. In general, the improvement of the soot oxidation is observed over the Pt impregnated CeO₂ and CeReO_x catalysts, and can be correlated to the presence of Pt°. The surface reduction of the supports in the presence of Pt occurred below 100 °C. The surface redox properties of the support in the Pt catalysts do not have a significant role in the NO to NO₂ conversion. In spite of the lower surface area, the Pt/CeYO_x and Pt/CeO₂ catalysts are found to be more active due to larger Pt crystal sizes. The presence of Pt also improved the CO conversion to CO₂ over these catalysts. The activation energy for the soot oxidation with NO + O₂ is found to be around 50 kJ/mol.     

Preparation and characterization of LaFe1−xMgxO3/Al2O3/FeCrAl: Catalytic properties in methane combustion

MnO_x–CeO₂ mixed oxides prepared by sol–gel method, coprecipitation method and modified coprecipitation method were investigated for the complete oxidation of formaldehyde. Structure analysis by H₂-TPR and XPS revealed that there were more Mn⁴⁺ species and richer lattice oxygen on the surface of the catalyst prepared by the modified coprecipitation method than those of the catalysts prepared by sol–gel and coprecipitation methods, resulting in much higher catalytic activity toward complete oxidation of formaldehyde. The effect of calcination temperature on the structural features and catalytic behavior of the MnO_x–CeO₂ mixed oxides prepared by the modified coprecipitation was further examined, and the catalyst calcined at 773 K showed 100% formaldehyde conversion at a temperature as low as 373 K. For the samples calcined below 773 K, no any diffraction peak corresponding to manganese oxides could be detected by XRD measurement due to the formation of MnO_x–CeO₂ solid solution. While the diffraction peaks corresponding to MnO₂ phase in the samples calcined above 773 K were clearly observed, indicating the occurrence of phase segregation between MnO₂ and CeO₂. Accordingly, it was supposed that the strong interaction between MnO_x and CeO₂, which depends on the preparation route and the calcination temperature, played a crucial role in determining the catalytic activity toward the complete oxidation of formaldehyde.     

Design and synthesis of ZnCo2O4/CdS for substantially improved photocatalytic hydrogen production

In this study, the hydrogen evolution performance of CdS nanorods is improved using ZnCo₂O₄. ZnCo₂O₄ nanospheres are synthesized using the hydrothermal and calcination methods, and CdS nanorods are synthesized using the solvothermal method. From the perspective of morphology, numerous CdS nanorods are anchored on the ZnCo₂O₄ microspheres. According to the experimental results of photocatalytic hydrogen evolution, the final hydrogen evolution capacity of 7417.5 μmol∙g^–1∙h^–1 is slightly more than two times that of the single CdS, which proves the feasibility of our study. Through various characterization methods, it is proved that the composite sample has suitable optoelectronic properties. In addition, ZnCo₂O₄ itself exhibits good conductivity and low impedance, which shortens the charge-transfer path. Overall, the introduction of ZnCo₂O₄ expands the adsorption range of light and improves the performance of photocatalytic hydrogen evolution. This design can provide reference for developing high-efficiency photocatalysts.     

Catalytic reduction of NO by CO over NiO/CeO2 catalyst in stoichiometric NO/CO and NO/CO/O2 reaction

A new catalyst composed of nickel oxide and cerium oxide was studied with respect to its activity for NO reduction by CO under stoichiometric conditions in the absence as well as the presence of oxygen. Activity measurements of the NO/CO reaction were also conducted over NiO/γ-Al₂O₃, NiO/TiO₂, and NiO/CeO₂ catalysts for comparison purposes. The results showed that the conversion of NO and CO are dependent on the nature of supports, and the catalysts decreased in activity in the order of NiO/CeO₂ > NiO/γ-Al₂O₃ > NiO/TiO₂. Three kinds of CeO₂ were prepared and used as support for NiO. They are the CeO₂ prepared by (i) homogeneous precipitation (HP), (ii) precipitation (PC), and (iii) direct decomposition (DP) method. We found that the NiO/CeO₂(HP) catalyst was the most active, and complete conversion of NO and CO occurred at 210 °C at a space velocity of 120,000 h⁻¹. Based on the results of surface analysis, a reaction model for NO/CO interaction over NiO/CeO₂ has been proposed: (i) CO reduces surface oxygen to create vacant sites; (ii) on the vacant sites, NO dissociates to produce N₂; and (iii) the oxygen originated from NO dissociation is removed by CO.     

Potential rare earth modified CeO2 catalysts for soot oxidation: I. Characterisation and catalytic activity with O2

Ceria (CeO₂) and rare-earth modified ceria (CeReO_x with Re = La, Pr, Sm, Y) catalysts are prepared by nitrate precursor calcination and are characterised by BET surface area, XRD, H₂-TPR, and Raman spectroscopy. Potential of the catalysts in the soot oxidation is evaluated in TGA with a feed gas containing O₂. Seven hundred degree Celsius calcination leads to a decrease in the surface area of the rare-earth modified CeO₂ compared with CeO₂. However, an increase in the meso/macro pore volume, an important parameter for the soot oxidation with O₂, is observed. Rare-earth ion doping led to the stabilisation of the CeO₂ surface area when calcined at 1000 °C. XRD, H₂-TPR, and Raman characterisation show a solid solution formation in most of the mixed oxide catalysts. Surface segregation of dopant and even separate phases, in CeSmO_x and CeYO_x catalysts, are, however, observed. CePrO_x and CeLaO_x catalysts show superior soot oxidation activity (100% soot oxidation below 550 °C) compared with CeSmO_x, CeYO_x, and CeO₂. The improved soot oxidation activity of rare-earth doped CeO₂ catalysts with O₂ can be correlated with the increased meso/micro pore volume and stabilisation of external surface area. The segregation of the phases and the enrichment of the catalyst surface with unreducible dopant decrease the intrinsic soot oxidation activity of the potential CeO₂ catalytic sites. Doping CeO₂ with a reducible ion such as Pr^4+/3+ shows an increase in the soot oxidation. However, the ease of catalyst reduction and the bulk oxygen-storage capacity is not a critical parameter in the determination of the soot oxidation activity. During the soot oxidation with O₂, the function of the catalyst is to increase the ‘active oxygen’ transfer to the soot surface, but it does not change the rate-determining step, as evident from the unchanged apparent activation energy (around 150 kJ mol⁻¹), for the catalysed and un-catalysed soot oxidation. Spill over of oxygen on the soot surface and its subsequent adsorption at the active carbon sites is an important intermediate step in the soot oxidation mechanism.     

Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity

Co₃O₄/CeO₂ composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co₃O₄) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co₃O₄ and CeO₂ were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out.

An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co₃O₄ in correspondence of Co₃O₄–CeO₂ containing 30% by weight of Co₃O₄. The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co₃O₄ phase and promoting the efficiency of the Co³⁺–Co²⁺ redox couple. The presence in the sample Co₃O₄(30 wt.%)–CeO₂ of a high relative amount of Ce³⁺/(Ce⁴⁺ + Ce³⁺) as detected by XPS confirms the enhanced oxygen mobility.

The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co₃O₄ phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750 °C for 7 h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co₃O₄ and Co₃O₄(30 wt.%)–CeO₂, performing the tests in the presence of 5 vol.% H₂O. A methane oxidation test upon hydrothermal ageing (flowing at 600 °C for 16 h a mixture 5 vol.% H₂O + 5 vol.%O₂ in He) of the Co₃O₄(30 wt.%)–CeO₂ sample was also performed. All the results confirm the superiority of this composite oxide.     

NiCo2O4@quinone-rich N–C core–shell nanowires as composite electrode for electric double layer capacitor

The bind-free carbon cloth-supported electrodes hold the promises for high-performance electrochemical capacitors with high specific capacitance and good cyclic stability. Considering the close connection between their performance and the amount of carbon material loaded on the electrodes, in this work, NiCo₂O₄ nanowires were firstly grown on the substrate of active carbon cloth to provide the necessary surface area in the longitudinal direction. Then, the quinone-rich nitrogen-doped carbon shell structure was formed around NiCo₂O₄ nanowires, and the obtained composite was used as electrode for electric double layer capacitor. The results showed that the composite electrode displayed an area-specific capacitance of 1794 mF∙cm^–2 at the current density of 1 mA∙cm^–2. The assembled symmetric electric double layer capacitor achieved a high energy density of 6.55 mW∙h∙cm^–3 at a power density of 180 mW∙cm^–3. The assembled symmetric capacitor exhibited a capacitance retention of 88.96% after 10000 charge/discharge cycles at the current density of 20 mA∙cm^–2. These results indicated the potentials in the preparation of the carbon electrode materials with high energy density and good cycling stability.     

CeO2改性再生SCR催化剂的单质汞氧化特性

对国内某1000MW燃煤发电机组失活选择性催化还原（SCR）催化剂进行CeO₂改性再生。对再生前后样品进行N₂吸附-脱附、扫描电子显微镜（SEM）、X射线荧光光谱（XRF）、傅里叶变换红外光谱（FTIR）对比表征分析。在自制固定床反应系统上对CeO₂改性再生催化剂（CeReCat）进行Hg⁰氧化性能测试,同时研究了SO₂、H₂O、NO和NH₃对Hg⁰氧化性能的影响。结果表明,CeO₂改性再生方法可有效清洗失活SCR催化剂表面杂质,恢复催化剂表面活性位点和孔隙结构,可使Ce、V两种活性元素得到有效负载。CeO₂改性后的样品Hg⁰氧化性能显著提升,3.0 CeReCat具有最佳Hg⁰的氧化效率。此外,烟气中加入600μL/L SO₂后,3.0 CeReCat仍具有高达74.4%的Hg⁰氧化效率,抗SO₂性能较好。烟气中的NO可轻微促进Hg⁰的氧化。由于竞争吸附作用,烟气中的H₂O和NH₃会抑制Hg⁰的氧化。CeO₂改性再生催化剂置于SCR系统下层时,由于烟气NH₃浓度较低而具有较高Hg⁰氧化效率,具有良好的应用前景。     

CH4/CO2 reforming over La2NiO4 and 10%NiO/CeO2–La2O3 catalysts under the condition of supersonic jet expansion via cavity ring-down spectroscopic analysis

CH₄/CO₂ reforming over La₂NiO₄ and 10%NiO/CeO₂–La₂O₃ catalysts under the condition of supersonic jet expansion was studied via direct monitoring of the reactants and products using the sensitive technique of cavity ring-down spectroscopy. Vibration–rotational absorption lines of CH₄, H₂O, CO₂ and CO molecules were recorded in the near infrared spectral region. Our results indicated that La₂NiO₄ is superior to 10%NiO/CeO₂–La₂O₃ in performance. In addition, we observed enhanced reverse-water-gas-shift reaction at augmented reaction temperature. The formation of reaction intermediates was also investigated by means of time-of-flight mass spectrometry and there was the detection of CH_x⁺, OH⁺ and H⁺ species.