Microstructure and activity of Pd catalysts prepared on commercial carbon support for the liquid phase decomposition of formic acid

In this work, a series of Pd catalysts supported on commercially available activated carbon (Norit ®) were prepared by employing different metal precursors (Pd(NO₃)₂ and Na₂PdCl₄) by the impregnation-reduction method at different pH. Catalysts were tested for the liquid phase decomposition of formic acid to generate hydrogen. The best results, in terms of small particle size and high catalytic activity were achieved for the Pd/C sample prepared by using Pd(NO₃)₂ salt impregnated at pH = 2.5, and reduced with sodium borohydride. The particle size of the best Pd/C catalyst is (4.1 ± 1.4) nm with initial TOFs of 2929 and 683 h^?1 at 60 and 30 °C respectively and an apparent activation energy of 40 kJ mol^?1. Samples prepared by using Na₂PdCl₄ precursor, consisted of particles with higher size and thus lower activity than the ones prepared with Pd(NO₃)₂. Regardless the Pd precursor employed, the best results in terms of particle size and activity were achieved at the point of zero charge of the support when the Pd species and the carbon surface were both neutral. The impregnation pH not only determines the particle size, but also the nature of the reducing agent does. The catalytic activity was shown to be size-dependent and it was shown that a mixture of surface Pd⁰ and Pd^II oxidation states is beneficial for the activity. When comparing with literature catalysts with similar composition, we found that our best catalyst is competitive enough and that Norit ® support could be promising for future studies on this reaction.     

Low-temperature CO preferential oxidation in H2-rich stream over iron modified Pd–Cu/hydroxyapatite catalyst

The effect of FeCl₃ addition on the catalytic property of Pd–Cu/hydroxyapatite (Pd–Cu/HAP) for low-temperature CO preferential oxidation (CO-PROX) under H₂-rich condition has been investigated. It can be found that CO conversion of Pd–Cu/HAP rapidly decreases from 56% to 21% within 2 h at 30 °C in the presence of water, however, the Pd–Cu–Fe/HAP with the Fe/Cu atomic ratio of 1:1 presents a stable CO conversion of 40% and CO₂ selectivity of 100% under the same reaction conditions. The characterization results display that the addition of FeCl₃ to Pd–Cu/HAP causes the formation of Fe₂O₃ species, and the strong interaction presents between Fe₂O₃ species and Pd–Cu/HAP. Thus, the Pd⁰ species generated during CO-PROX over Pd–Cu–Fe/HAP can be more easily oxidized than that over Pd–Cu/HAP, which could avoid H₂ adsorption on Pd⁰ species and maintain CO adsorption and activation.     

Syngas production via partial oxidation of dimethyl ether over Rh/Ce0.75Zr0.25O2 catalyst and its application for SOFC feeding

Dimethyl ether (DME) partial oxidation (PO) was studied over 1 wt% Rh/Ce_0.75Zr_0.25O₂ catalyst at temperatures 300–700 °C, O₂:C molar ratio of 0.25 and GHSV 10000 h⁻¹. The catalyst was active and stable under reaction conditions. Complete conversion of DME was reached at 500 °C, but equilibrium product distribution was observed only at T ≥ 650 °C. High concentration of CH₄ and low contents of CO and H₂ were observed at 500–625 °C 75 cm³ of composite catalyst 0.24 wt% Rh/Ce_0.75Zr_0.25O₂/Al₂O₃/FeCrAl showed excellent catalytic performance in DME PO at O₂:C molar ratio of 0.29 and inlet temperature 840 °C which corresponded to carbon-free region. 100% DME conversion was reached at GHSV of 45,000 h⁻¹. The produced syngas contained (vol. %): 33.4 H₂, 34.8 N₂, 22.7 CO, 3.6 CO₂ and 1.6 CH₄. Composite catalyst demonstrated the specific syngas productivity (based on CO and H₂) in DME PO of 42.8 m³·L_cat⁻¹·h⁻¹ (STP) and the syngas productivity of more than 3 m³·h⁻¹ (STP) that was sufficient for 3 kW_e SOFC feeding. PO of natural gas and liquified petroleum gas can be carried out over the same catalyst with similar productivity, realizing the concept of multifuel hydrogen generation. The syngas composition obtained via DME PO was shown to be sufficient for YSZ-based SOFC feeding.     

Fe–N–Si tri-doped carbon nanofibers for efficient oxygen reduction reaction in alkaline and acidic media

The most ideal substitute for Pt/C to catalyze the oxygen reduction reaction (ORR) is the transition metal and nitrogen co-doped carbon-based material (TM-N-C). However, large particles with low catalytic activity are formed easily for the transition metals during high-temperature carbonization. Herein, PAN nanofibers uniformly distributed with FeCl₃ were coated with SiO₂ and then carbonized to obtain Fe–N–Si tri-doped carbon nanofibers catalyst (Fe–N–Si-CNFs). The SiO₂ can further anchor the Fe atoms, thus preventing agglomeration during the carbonization process. Meanwhile, Si atoms have been doped in CNFs during this process, which is conducive to the further improvement of catalytic performance. The Fe–N–Si-CNFs catalyst has a 3D network structure and a large specific surface area (809.3 m² g⁻¹), which contributes to catalyzing the ORR. In alkaline media, Fe–N–Si-CNFs exhibits superior catalytic performance (E_1/2 = 0.86 V vs. RHE) and higher stability (9.6% activity attenuation after 20000s) than Pt/C catalyst (20 wt%).     

Mn-induced Cu/Ce catalysts with improved performance for CO preferential oxidation in H2/CO2-rich streams

A series of xMnCu/Ce catalysts with constant low Cu loading of 1 wt% were prepared by the simple impregnation method. The obtained catalysts were characterized by XRD, BET, H₂-TPR and XPS, and the preferential oxidation of CO was evaluated in CO₂/H₂-rich atmospheres. It was shown that partial Mn and Cu could be incorporated into the Ceria lattice, forming surface ternary Cu–Mn–Ce oxide solid solutions. At Mn/Cu = 0.6, the catalyst presented strong interaction among Cu, Mn and Ce, had more Ce³⁺ and Mn⁴⁺ at the surface and showed the best catalytic performance, making CO conversion increase of 23.57% at 90 °C as compared with the Cu/Ce catalyst. For CO-Prox, the highest CO conversion was 94.7% with an oxidation selectivity of 78.9% at 125 °C. At this temperature, the catalyst revealed stable catalytic performance for a total TOS of 205 h. In addition, with CO/Ar as feed gas, CO conversion was 100%, confirming the negative effects of CO₂/H₂.     

Investigation of flame spray synthesized La1-xSrxCoO3 perovskites with promotional catalytic performances on CO oxidation

To enhance the activity of catalysts for CO removal, the perovskite-type catalysts La_1-xSr_xCoO₃ (x = 0, 0.2, 0.4, 0.6, and 0.8) with different Sr²⁺ doping amount were synthesized by flame spray synthesis (FSS) method. The perovskite-type catalyst synthesized by FSS has a much larger specific surface area (SSA) than that prepared by other conventional methods. The SSA of catalyst increases with the increase of Sr²⁺ doping amount and the SSA of La_0.2Sr_0.8CoO₃ reaches 31.65 m²/g. Compared with other conventional methods, FSS method significantly improves the activity of catalyst and makes it close to the performances of catalysts with surface modification. The substitution of La³⁺ by Sr²⁺ promotes the generation of secondary phase Co₃O₄ and SrCO₃. The catalytic activity of La_1-xSr_xCoO₃ increases with the addition of Sr²⁺, which results from the increasing active sites and oxygen vacancies. Interestingly, La_0.4Sr_0.6CoO₃ performs the highest activity for CO oxidation and the CO conversion reaches 50% at 148.6 °C and 90% at 165.9 °C. The oxidation of CO over La_1-xSr_xCoO₃ catalyst may follow a combination of MvK and L-H mechanisms according to the experimental results of H₂-TPR. Moreover, the catalyst exhibits good catalytic activity in consecutive oxidation cycles. In consecutive oxidation experiments with La_0.4Sr_0.6CoO₃, the CO conversion reaches 50% at 168.8 °C and 90% at 197.8 °C in the eighth oxidation cycle. These results prove that FSS method can further improve the activity of catalysts and is suitable for the preparation of efficient catalysts.     

Lowering risk of methanation of carbon support in Ru/carbon catalysts for CO methanation by adding lanthanum

Two series of Ru/C catalysts doped with lanthanum ions are prepared and studied in CO methanation in the H₂-rich gas. The samples are characterized by N₂ physisorption, TG-MS studies, XRD, XPS, TEM/STEM and CO chemisorption. Two graphitized carbons differing in surface area (115 and 80.6 m²/g) are used as supports. The average sizes of ruthenium crystallites deposited on their surfaces are 4.33 and 5.95 nm, respectively. The addition of the proper amount of La to the Ru/carbon catalysts leads to an above 20% increase in the catalytic activity along with stable CH₄ selectivity higher than 99% at all temperatures. Simultaneously, lanthanum acts as the inhibitor of methanation of the carbon support under conditions of high temperature and hydrogen atmosphere. Such positive effects are achieved at a very low concentration of La in the prepared samples, a maximum 0.04 La/Ru (molar ratio). 0.01 mmol La introduced to the Ru/C system leads to 98% CO conversion at 270 °C.     

Influence of hydrogen and carbon monoxide on reduction behavior of iron oxide at high temperature: Effect on reduction gas concentrations

The purposes of this study are to reduce Fe₂O₃ using hydrogen (H₂) and carbon monoxide (CO) gases at a high temperature zone (500 °C–900 °C) by focusing on the influence of reduction gas concentrations. Reduction behavior of hematite (Fe₂O₃) at high temperature was examined using temperature programmed reduction (TPR) under non-isothermal conditions with the presence of 10% H₂/N₂, 20% H₂/N₂, 10% CO/N₂, 20% CO/N₂ and 40% CO/N₂. The TPR_CO results indicated that the first and second reduction peaks of Fe₂O₃ at a temperature below 660 °C appeared rapidly when compared to TPR_H2. However, TPR_H2 exhibited a better reduction in which Fe₂O₃ entirely reduced to Fe at temperature 800 °C (20% H₂) without any remaining of wustite (FeO) whereas a temperature above 900 °C is needed for a complete reduction in 10% H₂/N₂, 10% and 20% CO/N₂. Furthermore, the reduction of hematite could be improved when increasing CO and H₂ concentrations since reduction profiles were shifted to a lower temperature. Thermodynamic calculation has shown that enthalpy change of reaction (ΔHr) for all phases transformation in CO atmosphere is significantly lower than in H₂. This disclosed that CO is the best reductant as it is a more exothermic, more spontaneous reaction and able to initiate the reduction at a much lower temperature than H₂ atmosphere. Nevertheless, the reduction of hematite using CO completed at a temperature slightly higher compared to H₂. It is due to the presence of an additional carburization reaction which is a phase transformation of wustite to iron carbide (FeO → Fe₃C). Carburization started at the end of the second stage reduction at 600 °C and 630 °C under 20% and 40% CO, respectively. Therefore, reduction by CO encouraged the formation of carbide, slower the reduction and completed at high temperature. XRD analysis disclosed the formation of austenite during the final stage of a reduction under further exposure with high CO concentration. Overall, less energy consumption needed during the first and second stages of reduction by CO, the formation of iron carbide and austenite were enhanced with the presence of higher CO concentration. Meanwhile, H₂ has stimulated the formation of pure metallic iron (Fe), completed the reduction faster, considered as the strongest reducing agent than CO and these are effective at a higher temperature. Proposed iron phase transformation under different reducing agent concentrations are as followed: (a) 10% H₂, 20% H₂ and 10% C; Fe₂O₃ → Fe₃O₄ → FeO → Fe, (b) 20% CO; Fe₂O₃ → Fe₃O₄ → FeO → Fe₃C → Fe and (c) 40% CO; Fe₂O₃ → Fe₃O₄ → FeO → Fe₃C → Fe → F,C (austenite).     

Influence of hydrogen and various carbon monoxide concentrations on reduction behavior of iron oxide at low temperature

The aims of this study are to produce Fe₃O₄ from Fe₂O₃ using hydrogen (H₂) and carbon monoxide (CO) gases by focusing on the influence of these gases on reduction of Fe₂O₃ to Fe₃O₄ at low temperature (below 500 °C). Low reduction temperature behavior was investigated by using temperature programmed reduction (TPR) with the presence of 20% H₂/N₂, 10% CO/N₂, 20% CO/N₂ and 40% CO/N₂. The TPR results indicated that the first reduction peak of Fe₂O₃ at low temperature appeared faster in CO atmosphere compared to H₂. Furthermore, reducibility of first stage reduction could be improved when increasing CO concentration and reduction rate were followed the sequence as: 40% CO > 20% CO > 10% CO > 10% H₂. All reduction peaks were shifted to higher temperature when the CO concentration was reduced. Although, initial reduction by H₂ occurred slower (first peak appeared at higher temperature, 465 °C) compared to CO, however, it showed better reduction with Fe₂O₃ fully reduced to Fe at temperature below 800 °C. Meanwhile, complete reduction happened at temperature above 800 °C in 10% and 20% CO/N₂. Thermodynamic calculation revealed that CO acts as a better reducer than H₂ as the enthalpy change of reaction (ΔH_r) is more exothermic than H₂ and the change in Gibbs free energy (ΔG) at 500 °C is directed to more spontaneous reaction in converting Fe₂O₃ to Fe₃O₄. Therefore, formation of magnetite at low temperature was thermodynamically more favorable in CO compared to H₂ atmosphere. XRD analysis explained the formation of smaller crystallite size of magnetite by H₂ whereas reduction of CO concentration from 40, 20 to 10% enhanced the growth of highly crystalline magnetite (31.3, 35.5 and 39.9 nm respectively). All reductants were successfully transformed Fe₂O₃ → Fe₃O₄ at the first reduction peak except for 10% CO/N₂ as there was a weak crystalline peak due to remaining unreduced Fe₂O₃. Overall, less energy consumption needed in reducing Fe₂O₃ to Fe₃O₄ by CO. This proved that CO was enhanced the formation of magnetite, encouraged formation of highly crystalline magnetite in more concentrated CO, considered better reducing agent than H₂ and these are valid at lower temperature.     

Electrospun NiMn2O4 and NiCo2O4 spinel oxides supported on carbon nanofibers as electrocatalysts for the oxygen evolution reaction in an anion exchange membrane-based electrolysis cell

Spinel oxide electrocatalysts supported on carbon nanofibers (CNFs), denoted as and NiMn₂O₄/CNF and NiCo₂O₄/CNF, are investigated for the oxygen evolution reaction (OER) in alkaline electrolyte. NiCo₂O₄/CNF and NiMn₂O₄/CNF are prepared according to an optimized electrospinning method using polyacrylonitrile (PAN) as carbon nanofibers precursor. After the thermal treatment at 900 °C for 1 h in the presence of helium and the subsequent one at 350 °C for 1 h in air, nanosized metal oxides with a spinel structure supported on carbon nanofibers are obtained. The physico-chemical investigation shows relevant difference in the crystallite size (9 nm for the NiCo₂O₄/CNF and 20 nm for the NiMn₂O₄/CNF) and a more homogeneous distribution for NiMn₂O₄ supported on carbon nanofibers. These characteristics derive from the different catalytic effects of Co and Mn during the thermal treatment as demonstrated by thermal analysis. The OER activity of NiCo₂O₄/CNF and NiMn₂O₄/CNF is studied in a single cell based on a zero gap anion-exchange membrane-electrode assembly (MEA). The NiMn₂O₄/CNF shows a better mass activity than NiCo₂O₄/CNF at 50 °C (116 A g⁻¹ @ 1.5 V and 362 A g⁻¹ @ 1.8 V vs. 39 A g⁻¹ @ 1.5 V and 253 A g⁻¹ @ 1.8 V) but lower current density at specific potentials. This is the consequence of a lower concentration of the active phase on the support resulting from the need to mitigate the particle growth in NiMn₂O₄/CNF.     

Catalytic behaviour of Mn2.94M0.06O4-δ (M=Pt,Ru and Pd) catalysts for low temperature water gas shift (WGS) and CO oxidation

Noble metal (Pt, Ru and Pd) substituted Mn₃O₄ catalysts have been synthesized in this work by a sonochemical route. The catalysts were characterised by XRD, XPS, TEM, H₂-TPR and BET surface area analyser and the activity of these catalysts was tested towards low temperature water gas shift reaction (WGS) and CO oxidation reaction. It was observed that these catalysts have the tetragonal crystalline structure of Mn₃O₄ and the average particle size was found in the range of 12 nm–22 nm. H₂-TPR results show that the strong metal support interaction between substituted metal and Mn₃O₄ leads to high reducibility and makes these catalysts active for WGS and CO oxidation. Pt substituted Mn₃O₄ showed higher activity towards WGS compared to other synthesized catalysts and 99.9% conversion was observed at 260 °C without methane formation. The activation energy of Mn_2.94Pt_0.06O_4-δ was found to be 59 ± 0.6 kJ/mol. DRIFTS analysis was carried out to propose the reaction mechanism for water gas shift and CO oxidation. Redox mechanism was hypothesized for WGS and used to correlate the experimental data over Pt substituted Mn₃O₄. Similarly, kinetic parameters were estimated based on Langmuir-Hinshelwood mechanism for CO oxidation over Pd substituted Mn₃O₄ which showed better activity compare to other synthesized catalysts and 99.9% conversion was observed at 175 °C. The activation energy was calculated from Arrhenius plot which was found to be 30 ± 0.4 kJ/mol.     

Synergistic tuning of the phase structure of alumina and ceria-zirconia in supported palladium catalysts for enhanced methane combustion

CeO₂–ZrO₂–Al₂O₃ composite oxides supported palladium catalysts (Pd/CZA) are promising candidates for catalytic oxidation reactions. However, the efficient and stable oxidation of methane over Pd-based catalysts remains a longstanding challenge. Herein, we present a facile strategy to boost the catalytic performance of Pd/CZA through elaborately tuning the phase structure of supports. Calcining supports at relatively high temperatures (1200, 1300 °C) induced the phase transition of alumina (from γ-to α-) and the development of CeO₂–ZrO₂ solid solution (CZ). The weak interaction between α-Al₂O₃ and PdO resulted in an improved reducibility of catalysts. Meanwhile, the higher oxygen mobility originated from well-crystallized CZ phase contributed to the reoxidation of Pd to PdO, giving rise to abundant surface active Pd²⁺ species. Coupled with the hydrophobicity of α-Al₂O₃, the catalyst prepared with CZA supports calcined at 1300 °C demonstrated an excellent low-temperature activity, astounding stability and greatly enhanced water resistance towards methane combustion.     

Graphitic carbon nitride‐chitosan composites–anchored palladium nanoparticles as high‐performance catalyst for ammonia borane hydrolysis

The novel composites consisting of graphitic carbon nitride and chitosan (denoted as g‐C₃N₄‐CS) is synthesized for anchoring palladium nanoparticles. The results reveal that the resultant catalysts possess superior catalytic activity for ammonia borane (AB) hydrolysis. The corresponding turnover frequency reaches up to 27.7 at 30.0°C, and the activation energy is as low as 35.3 kJ mol^?1. Kinetics study reveals that the hydrolysis reaction is 0.50 and 0.68 orders with AB concentration and palladium concentration, respectively. In addition, the catalytic activity of the resultant Pd(0)/g‐C₃N₄‐CS catalysts is stable even after 10 runs. The result will be helpful for the development of hydrogen generation and functional materials.     

CO preferential oxidation in H2-rich stream over the CuO-MnOx mixed oxide catalysts prepared by a facile mechanochemical preparation method

The CuMn samples with various CuO weight percentages were synthesized by the mechanochemical route. The catalytic activity of the prepared samples was determined in the preferential oxidation of CO process (CO-PROX) in the temperature range of 40–250 °C. According to the XRD results, the 5CuMn and 10CuMn samples exhibited the spinel phase in their structures. The spinel phase formation enhanced the CO adsorption active sites and modified the redox properties. The results indicated that the copper incorporation into the manganese oxide modified the catalytic activity and structural properties. The 5CuMn catalyst with the highest BET area (72.1 m² g⁻¹) possessed 96% CO conversion and 50% CO₂ selectivity at 70 °C (GHSV = 30,000 ml/h.g_cat) and significant resistance in the presence of water due to the formation of hydroxyl groups over the catalyst surface. The catalyst activity remained stable for 14 h at 130 °C. Furthermore, the influence of calcination temperature, feed composition, and GHSV value on the catalytic performance of the 5CuMn catalyst was studied.     

Catalytic characteristics of CexCu1-xO1.9 catalysts formed by solid state method for MTS and OMTS reactions

Ce_xCu_1-xO_1.9 (x = 0.3, 0.5, 0.8 and 0.9) catalysts were synthesized by solid state method, using ball mill apparatus, and evaluated in medium temperature shift (MTS), as well as oxygen assisted MTS (OMTS) reactions at temperature range of 300–390 °C. Catalysts were characterized by X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Scanning Electron Microscopy (SEM), and N₂ adsorption-desorption (BET) analysis. Ce_0.9Cu_0.1O_1.9 sample showed the best catalytic activity and structural properties. Decrease in proportion of Cu to Ce, leads to increase in the Cu-Ce mixed oxide formation (according to TPR analysis), significant increase in BET surface area (from 18 m²/g for Ce_0.3Cu_0.7O_1.9–48 m²/g for Ce_0.9Cu_0.1O_1.9), and decrease in CuO crystalline size (XRD). Moreover, the effect of oxygen addition to the feed (O₂/CO ratio = 0, 0.3, 0.5, 0.7 and 1), on the catalytic performance was evaluated. CO conversion was increased by enhancing the amount of oxygen (from 60% to 80% at 360 °C). CO and H₂ oxidations are occurring as competitive parallel reactions in which CO oxidation is dominant at low O₂/CO ratios (<0.5) and H₂ oxidation (undesirable for MTS reaction) at high O₂/CO ratios (>0.5). Furthermore, molar ratios of steam to CO at ranges of 2–4 were compared in OMTS reaction. According to the obtained results, the magnitudes of O₂/CO ratio and S/C ratio which were 0.5 and 4, respectively, were selected as the best values for OMTS reaction.     

Fe0.5Co0.5-Co1.15Fe1.15O4/carbon composite nanofibers prepared by solution blow spinning: Structure,morphology, Mössbauer spectroscopy,and application as catalysts for electrochemical water oxidation

In this work, we report the synthesis of Fe_0.5Co_0.5-Co_1.15Fe_1.15O₄/carbon composite nanofibers by solution blow spinning (SBS) and study their structure, morphology, and catalytic activity toward the oxygen evolution reaction (OER, electrochemical water oxidation) in an alkaline medium. The solution blow spun fibers, prepared using nitrate precursors (Fe and Co) and poly(vinyl pyrrolidone, PVP), were calcined at 620 °C for 1 h in argon atmosphere. The thermogravimetric test shows that the stabilization of mass loss and the formation of the compound occur at ～600 °C. X-ray diffraction revealed the presence of two crystalline phases, Fe_0.5Co_0.5 and Co_1.15Fe_1.15O₄, with crystallite sizes of 16.5 nm and 18.1 nm, respectively. Scanning and transmission electron microscopies show that the average fiber and nanoparticle diameters are 362 nm and 28.41 nm, respectively. The quantification of Fe_0.5Co_0.5 and Co_1.15Fe_1.15O₄ phases determined by the Rietveld refinement agrees well with the relative absorption area (RAA) values obtained by Mössbauer spectroscopy. Electrochemical analyses of Fe_0.5Co_0.5-Co_1.15Fe_1.15O₄/carbon composite nanofibers supported by commercial Ni foam reveal a low overpotential value of η = 308 mV at 10 mA cm^?2 and only 400 mV to generate 450 mA cm^?2. The chronopotentiometry test over 15 h indicates that Fe_0.5Co_0.5-Co_1.15Fe_1.15O₄/carbon nanofibers have excellent chemical and mechanical stability for their use as electrodes for water oxidation.     

High jolt-resistance monolithic CuO–CeO2/AlOOH/Al-fiber catalyst for CO-PROX: Influence of AlOOH/Al-fiber calcination on Cu–Ce interaction

Micro-reactors for the preferential oxidation of CO in H₂-rich stream (CO-PROX) are attractive for PEMFCs employed in portable electronic devices and automobiles, but the jolt is inevitable, which makes micro-reactors necessitate high jolt resistance. The monolithic structured catalyst could effectively resolve these problems. Herein, we employed the thin-felt monolithic Al-fiber substrate to fabricate the CuO–CeO₂/AlOOH/Al-fiber catalyst for the CO-PROX reaction. This catalyst was prepared via first growing AlOOH nanosheets onto the Al-fiber surface by steam oxidation method, followed by depositing CuO–CeO₂ onto the AlOOH/Al-fiber support. The preferred catalyst delivered 100% CO conversion and 81% O₂ selectivity at 140 °C with a gas hourly space velocity of 12,000 mL g^?1 h^?1, and particularly, performed stably for 120 h at the changeable temperatures of 120–160 °C. This work provides a strategy to tailor a qualified monolithic catalyst that couples the promising jolt resistance and catalytic performance at 120–160 °C.     

Direct conversion of methane into methanol and ethanol via spherical Au@Cs2[closo-B12H12]and Pd@Cs2[closo-B12H12] nanoparticles

In this present study, novel aqueous-phase catalytic systems, namely spherical Au and Pd nanoparticles (NPs) capped with Cs₂ [closo-B₁₂H₁₂], were used to produce ethanol and methanol via direct oxidation of methane in the presence of H₂O₂ and O₂ under mild conditions. The ethanol selectivity surpassed 52.96% and 86.33% at 50 °C, and the productivity reached 8.86 and 25.18 mol·kgcat^–1·h^–1, respectively. Plausible methane–ethane–ethanol pathway involving free radial •OH radicals was proposed based on the electron paramagnetic resonance (EPR) result. According to the theoretical calculations, the surfaces of {111} plane of Au NPs and {100} plane of Pd NPs were capped with Cs₂ [closo-B₁₂H₁₂], and Au–B and Pd–B bonds were consequently formed, respectively. Moreover, the binding energies of Au NPs and Pd NPs capped with Cs₂ [closo-B₁₂H₁₂] were calculated to be −128.9 and −230.1 kcal mol⁻¹, respectively. Based on the theoretical calculations, higher binding energy indicates a larger amount of charge on the surfaces of the planes of NPs. A lower peak intensity can lead to the formation of a more stable catalyst with enhanced catalytic activity. Thus, the ethanol selectivity of the as-prepared catalyst was considerably higher than that for methanol.     

Preparation of Cu0.1-xNixCe0.9O2-y catalyst by ball milling and its CO catalytic oxidation performance

A series of Cu_0.1-xNi_xCe_0.9O_2-y catalysts with different Cu/Ni molar ratios were prepared by the ball milling method. The obtained catalytic materials were characterized by XRD, H₂-TPR, BET, XPS and Ramen and the effects of different Cu/Ni content on the structure, properties and CO catalytic oxidation performance of the catalysts were explored. The results evidenced the formation of Cu–Ni–Ce mixed oxide solid solution in all ternary catalysts. In addition, there is a synergistic interaction between Cu and Ni in ternary catalysts, resulting in more oxygen vacancies and improved reduction performance, and hence demonstrating better CO catalytic oxidation activity in the ternary catalysts than binary ones. Under a GHSV of 60000 mL·g_cat⁻¹·h⁻¹, the required reaction temperature for reaching less than 10 ppm CO is lowed from 160 °C with Cu_0·1Ce_0·9O_2-y to 130 °C with Cu_0·07Ni_0·03Ce_0·9O_2-y.     

Mechanisms of synthesis gas production via thermochemical cycles over La0·3Sr0·7Co0·7Fe0·3O3

La_0·3Sr_0·7Co_0·7Fe_0·3O₃ (LSCF3773) was chosen as an oxygen carrier material for synthesis gas production and synthesized using ethylene-diamine-tetra-acetic acid (EDTA) citrate-complexing method. LSCF exhibited a pure cubic structure where 110 and 100 plane diffractions were active for CO₂ splitting, while 111 was more favored by H₂O splitting. Overall oxygen storage capacity (OSC) of LSCF was 4072 μmol/g_cat. During the reduction process, regular cations (Co⁴⁺, Fe⁴⁺), polaron cations (Co³⁺, Fe³⁺) and localized cations (Co²⁺, Fe²⁺) were achieved when the LSCF was reduced at 500, 700 and 900 °C, respectively. The strength of the active sites depended on reduction temperatures. An increase in oxidation temperature enhanced H₂ production at temperature ranging from 500 °C to 700 °C while effected CO production at 900 °C. H₂O and CO₂ was competitively split during the oxidation step, especially at 700 °C. The activation energy of each reaction was ordered as; CO₂ splitting > H₂O splitting > CO₂ adsorption, supporting the above evidence where H₂ and CO production were found to increase when the operating temperature was increased.