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The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO2 and CH4 into syngas, a mixture of CO and H2. Ni-based catalysts have been intensively investigated for their use in the DRM. However, they are limited by the formation of carbonaceous materials on their surfaces. In this review, we explore carbon-induced catalyst deactivation mechanisms and summarize the recent research progress in controlling and mitigating carbon deposition by developing coke-resistant Ni-based catalysts. This review emphasizes the significance of support, alloy, and catalyst structural strategies, and the importance of comprehending the interactions between catalyst components to achieve improved catalytic performance and stability. [ABSTRACT FROM AUTHOR]

Ammonia decomposition is a key step in hydrogen production and is considered a promising practical intercontinental hydrogen carrier. In this study, 1 wt.% Ru/SiO2 catalysts were prepared via wet impregnation and subjected to calcination in air at different temperatures to control the particle size of Ru. Furthermore, silica supports with different surface areas were prepared after calcination at different temperatures and utilized to support a change in the Ru particle size distribution of Ru/SiO2. N2 physisorption and transmission electron microscopy were used to probe the textural properties and Ru particle size distribution of the catalysts, respectively. These results show that the Ru/SiO2 catalyst with a high-surface area achieved the highest ammonia conversion among catalysts at 400 °C. Notably, this is closely related to the Ru particle sizes ranging between 5 and 6 nm, which supports the notion that ammonia decomposition is a structure-sensitive reaction. [ABSTRACT FROM AUTHOR]

In this study, a Cu-promoted Fe/ZSM-5 catalyst was examined to reveal the effects of Cu species in selective oxidation of methane into methane oxygenates using H2O2 in water. Cu/ZSM-5, Cu-Fe/ZSM-5, and Fe/ZSM-5 catalysts were prepared using wet impregnation, solid-state ion exchange, and ion-exchange methods. Various techniques, including nitrogen physisorption, temperature-programmed reduction with H2, UV-vis spectroscopy, and FT-IR spectroscopy after NO adsorption, were utilized to characterize the catalysts. The promotional effect of Cu on the Cu-Fe/ZSM-5 catalyst in terms of methanol selectivity was confirmed. The preparation method has a considerable influence on the catalyst performance, and the ion-exchange method is the most effective. However, leaching of the Cu species was observed during this reaction, which can affect the quantification of formic acid by 1H-NMR. The homogeneous Cu species increase hydrogen peroxide decomposition and CO2 selectivity, which is undesirable for this reaction. [ABSTRACT FROM AUTHOR]

Fe-ZSM-5 is an active catalyst for the selective oxidation of methane with H 2 O 2 in liquid water. To prepare the active Fe-ZSM-5 catalyst, the effect of the Fe precursor on the catalytic performance was examined. Additionally, two preparation methods, wet impregnation (WI) and ion-exchange (IE), were also applied. The prepared catalysts were characterized using various techniques, such as nitrogen physisorption, X-ray diffraction, UV–Vis spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy after NO adsorption (NO-FTIR). Fe-ZSM-5 prepared from FeCl 2 appears to be the most active among the Fe-ZSM-5 catalysts prepared from FeCl 2 , FeSO 4 , Fe(CH 3 CO 2) 2 , FeCl 3 , Fe 2 (SO 4) 3 , Fe(C 5 H 7 O 2) 3 , and Fe(NO 3) 3 using the WI method. For Fe-ZSM-5 catalysts prepared using the IE method, divalent Fe precursors, such as FeSO 4 , FeCl 2 , and Fe(CH 3 CO 2) 2 , are better than trivalent Fe precursors, such as Fe 2 (SO 4) 3 , FeCl 3 , and Fe(NO 3) 3 , in terms of catalytic activity. The active catalyst has the dominant extra-framework Fe2+ species probed with UV–Vis spectroscopy and NO-FTIR. [Display omitted] • Partial oxidation of CH 4 with H 2 O 2 in water was examined over Fe-ZSM-5. • The effect of Fe precursor during the catalyst preparation was investigated. • The active sites were probed with FT-IR spectroscopy after NO adsorption. • Correlation was made between the activity and the peak intensity in NO-FTIR spectra. [ABSTRACT FROM AUTHOR]

Abstract: Manganese oxide catalysts prepared by a precipitation method with various precipitants were investigated for the low temperature selective catalytic reduction (SCR) of NOx with NH3 in the presence of excess O2. Various characterization methods such as N2 adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and X-ray absorption near edge structure (XANES) were conducted to probe the physical and chemical properties of MnOx catalysts. The active MnOx catalysts, precipitated with sodium carbonate and calcined in air at moderate temperatures such as 523K and 623K, have the high surface area, the abundant Mn4+ species, and the high concentration of surface oxygen on the surface. The amorphous Mn3O4 and Mn2O3 were mainly present in this active catalyst. The carbonate species appeared to help adsorb NH3 on the catalyst surface, which resulted in the high catalytic activity at low temperatures. [Copyright &y& Elsevier]

In this study, unique core-shell aluminate spinel supports, Al@MAl2O4 (M = Zn, Mg, or Mn), were obtained by simple hydrothermal surface oxidation and were applied to the preparation of supported Ni catalysts for CO2 methanation. For comparison, CO methanation was also evaluated using the same catalysts. The prepared catalysts were characterized with a variety of techniques, including N2 physisorption, CO2 chemisorption, H2 chemisorption, temperature-programmed reduction with H2, temperature-programmed desorption of CO2, X-ray diffraction, high-resolution transmission electron microscopy, and in-situ diffuse reflectance infrared Fourier transform spectroscopy. The combination of supports with core-shell spinel structures and Ni doping with a deposition–precipitation method created outstanding catalytic performance of the Ni catalysts supported on Al@MgAl2O4 and Al@MnAl2O4 due to improved dispersion of Ni nanoparticles and creation of moderate basic sites with suitable strength. Good stability of Ni/Al@MnAl2O4 catalyst was also confirmed in the study. [ABSTRACT FROM AUTHOR]

The oxidative coupling of methane (OCM) is operated at high temperatures and is a highly exothermic reaction; thus, hotspots form on the catalyst surface during reaction unless the produced heat is removed. It is crucial to control the heat formed because surface hotspots can degrade catalytic performance. Herein, we report the preparation of Mn2O3-Na2WO4/SiC catalysts using SiC, which has high thermal conductivity and good stability at high temperatures, and the catalyst was applied to the OCM. Two Mn2O3-Na2WO4/SiC catalysts were prepared by wet-impregnation on SiC supports having different particle sizes. For comparison, the Mn2O3-Na2WO4/SiO2 catalyst was also prepared by the same method. The catalysts were analyzed by nitrogen adsorption–desorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The transformation of SiC into α-cristobalite was observed for the Mn2O3-Na2WO4/SiC catalysts. Because SiC was completely converted into α-cristobalite for the nano-sized SiC-supported Mn2O3-Na2WO4 catalyst, the catalytic performance for the OCM reaction of Mn2O3-Na2WO4/n-SiC was similar to that of Mn2O3-Na2WO4/SiO2. However, only the surface layer of SiC was transformed into α-cristobalite for the micro-sized SiC (m-SiC) in Mn2O3-Na2WO4/m-SiC, resulting in a SiC@α-cristobalite core–shell structure. The Mn2O3-Na2WO4/m-SiC showed higher methane conversion and C2+ yield at 800 and 850 °C than Mn2O3-Na2WO4/SiO2. [ABSTRACT FROM AUTHOR]

• Ni/SiO 2 catalysts were prepared from aqueous Ni(NO 3) 2 solutions by the precipitation method using Na 2 SiO 3. • This is a simple but efficient method to prepare well-dispersed NiO on silica. • The prepared catalysts were active for two model reactions, benzene hydrogenation and CO methanation. Ni/SiO 2 catalysts with high Ni content were prepared from aqueous Ni(NO 3) 2 solutions by the precipitation method using Na 2 SiO 3 as a silica precursor and precipitant. This is a simple but efficient method to prepare well-dispersed NiO on silica, which can be further transformed to Ni/SiO 2 through an additional reduction process. Various techniques such as nitrogen physisorption, X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (H 2 -TPR), hydrogen chemisorption, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were employed to characterize the catalysts. The prepared catalysts were applied to two model reactions, benzene hydrogenation and CO methanation. The catalyst showed significantly enhanced performance for these reactions compared to core-shell Ni@SiO 2 catalysts and conventional Ni/SiO 2 catalysts prepared by wet impregnation. [ABSTRACT FROM AUTHOR]

Abstract: The direct conversion of cellulose into polyols over Ni/W/SiO2-Al2O3 catalysts with different Al molar fractions was examined. For comparison, Cu/W/SiO2-Al2O3, Fe/W/SiO2-Al2O3, and Co/W/SiO2-Al2O3 were also evaluated. The bulk crystalline structure was determined using X-ray diffraction (XRD). The surface acidity was probed via temperature-programmed desorption of ammonia (NH3-TPD). The textural properties were investigated using N2 physisorption. The metal contents were confirmed via inductively coupled plasma–atomic emission spectroscopy (ICP-AES). Among the various metal catalysts, Ni/W/SiO2-Al2O3 was confirmed to be the most favorable for hydrogenolysis of cellulose into polyols. The effect of the Al molar fraction in SiO2-Al2O3 on this reaction over Ni/W/SiO2-Al2O3 was also investigated. It was found that the polyol yield was closely related to the total acidity of the support. Compared to Ni/W/SBA-15, Ni/W/SiO2-Al2O3 (Al/(Al+Si)=0.6) showed better stability during the recycling test. The catalyst deactivation was confirmed to be caused by metal leaching. [Copyright &y& Elsevier]

Abstract: The gas-phase dehydration of glycerol was conducted over silica–alumina catalysts with different Si/Al molar ratios. For comparison, SiO2 and η-Al2O3 were also examined. A variety of techniques, X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed oxidation (TPO) with mass spectroscopy (MS), infrared spectroscopy (FT-IR) after the adsorption of pyridine or glycerol, solid-state 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS/NMR) spectroscopy, Raman spectroscopy, and CHNS analysis, were employed to characterize the catalysts. The initial glycerol conversion at 315°C was strongly dependent on the total amount of acid sites over the silica–aluminas. The acrolein yield was proportional to the concentration of the Brønsted acid sites, whereas the 1-hydroxyacetone yield was proportional to the concentration of the Lewis acid sites. Among the tested catalysts, Si0.8Al0.2O x showed the highest acrolein selectivity during the initial 2h of the reaction. As long as the molar ratio between water and glycerol was in the range 2–11, the acrolein selectivity increased significantly with the water content of the feed. [Copyright &y& Elsevier]

Abstract: Three catalysts, 1wt.% Pt/Al2O3, 20wt.% Cu/Al2O3, and 1wt.% Pt–20wt.% Cu/Al2O3 were evaluated for the oxidation of NO by O2 and the selective catalytic reduction (SCR) of NO x by NH3 in the absence and presence of H2O. The Pt/Al2O3 catalyst exhibited the largest values in NO oxidation efficiency and NO x removal efficiency among the three catalysts. The presence of H2O caused a drop in the NO oxidation and the SCR activities. The SCR performance was significantly improved when Pt/Al2O3 and Cu/Al2O3 catalysts were employed sequentially in a reactor. The highest SCR performance was achieved using two separate stages: oxidation of NO by O2 over the Pt/Al2O3 catalyst followed by reduction of NO2 by NH3 over the Cu/Al2O3 catalyst. Under the condition with H2O, the two-stage catalyst system showed NO x removal efficiency over 80% at low temperatures below 200°C, which was the highest value among the catalyst systems used in this study. The physical and chemical properties of the catalysts were determined using nitrogen adsorption, XRD, TPR, and pulse CO chemisorption experiments. [Copyright &y& Elsevier]

[Display omitted] • Aqueous-phase partial oxidation of CH 4 with H 2 O 2 was examined over Fe-ZSM-5. • The effect of the catalyst preparation method for Fe-ZSM-5 was investigated. • Ion-exchange method is the most effective for the catalytic activity. • Isolated or oligonuclear extra-framework Fe species are proved to be most active. • The optimum Fe content exists to maximize the total product yield per consumed H 2 O 2. The effect of the catalyst preparation method on the catalytic activity of Fe-ZSM-5 for the partial oxidation of methane with H 2 O 2 in an aqueous phase was examined. UV–vis spectroscopy and FT-IR spectroscopy after NO adsorption were used to characterize the prepared catalysts. Various preparation methods, including wet impregnation, solid-state ion-exchange, chemical vapor impregnation, hydrothermal synthesis, and aqueous phase ion-exchange were compared. Among them, the aqueous phase ion-exchange method demonstrated the best results in producing isolated or oligonuclear extra-framework Fe species, which showed the highest catalytic activity. On the other hand, bulk iron oxides did not decompose H 2 O 2 nor did they activate methane. The total product yield and the amount of H 2 O 2 consumed increased with increasing Fe content in the case of the Fe-ZSM-5 catalyst prepared using an ion-exchange method. However, the fraction of less active Fe species, such as iron oxide clusters and larger iron oxide aggregates on the external crystal surface, increased with the Fe content, resulting in a decrease in the total product yield per Fe content and the amount of H 2 O 2 consumed per Fe content. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt/UiO66-xNH 2 catalysts were synthesized by the microwave-solvothermal method. • TOF Pt over Pt/UiO66-NH 2 catalysts were 1.8–3.2 times higher than that of Pt/UiO-66. • Transferring from DCOx to HDO reaction, confirmed by increase in C 18 /C 17 ratio. • Showing a good catalytic stability for coke deposition during HDO reaction. With the aim of developing more efficient catalysts based on MOF materials for biomass upgrading through the hydrodeoxygenation, a novel Pt/UiO-66-based catalyst was first designed by introducing amino groups, together with creating mixing-linker defect using 5-amino-isophthalic acid as a mixed linker, were successfully synthesized with a microwave-solvothermal method. XPS and CO-chemisorption measurements revealed that the presence of amino groups significantly enhance the reducibility of the PtCl 6 2- and PtCl 4 2- phases to the Pt0 phase. As a result, the catalytic performance of these catalysts in the HDO of oleic acid was enhanced, as demonstrated by the 1.8–3.2-fold higher turnover frequency compared to the original Pt/UiO-66 catalyst. Interestingly, the presence of amino-defective linker facilitated the transition from decarbonylation to the hydrodeoxygenation reaction, as confirmed by the significant increase in C 18 /C 17 ratio. Importantly, the modified catalysts were shown to possess a good catalytic stability, thus preventing coke deposition on the UiO-66 structure. [ABSTRACT FROM AUTHOR]

• Core–shell Al@Al2O3 was used as the support in supported Ni catalysts. • The Al@Al2O3 is better than γ-Al2O3 to develop a highly efficient Ni-based catalyst. • The deposition–precipitation method outperforms the wet impregnation method. • Higher Ni dispersion resulted in better catalytic performance for CO methanation. • The higher density of medium basic sites increases the CO 2 methanation activity. Core–shell Al@Al 2 O 3 , which was obtained by hydrothermal surface oxidation of Al metal particles, was used as the support in supported Ni catalysts for CO and CO 2 methanation. The core–shell micro-structured support (Al@Al 2 O 3) helped develop a highly efficient Ni-based catalyst compared with conventional γ-Al 2 O 3 for these reactions. Moreover, the deposition–precipitation method was shown to outperform the wet impregnation method in the preparation of the active supported Ni catalysts. The catalysts were characterized using various techniques, namely, N 2 physisorption, H 2 chemisorption, CO 2 chemisorption, temperature-programmed reduction with H 2 , temperature-programmed desorption after CO 2 adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, high-resolution transmission electron microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Higher Ni dispersion when using Al@Al 2 O 3 as the support and the deposition–precipitation method resulted in better catalytic performance for CO methanation. Furthermore, the higher density of medium basic sites and enhanced CO 2 adsorption capacity observed for Ni/Al@Al 2 O 3 helped increase catalytic activity for CO 2 methanation. [ABSTRACT FROM AUTHOR]

• Core-shell Al@γ-Al 2 O 3 was applied to the preferential CO oxidation in H 2 (PROX). • Ru/Al@γ-Al 2 O 3 shows the better PROX performance than Ru/α-Al 2 O 3 and Ru/γ-Al 2 O 3. • The effect of surface oxidation of Ru metal on PROX activity is important. • The surface oxidation of Ru metal on Al@γ-Al 2 O 3 was suppressed. • Ethanol-TPD reveals that Al@γ-Al 2 O 3 has different surface property with γ-Al 2 O 3. The Al@γ-Al 2 O 3 core-shell microstructures prepared from aluminum particles by hydrothermal surface oxidation were superior to the conventional alumina support owing to the facile heat flux through the metal-ceramic composite structures. The Ru catalysts supported on Al@γ-Al 2 O 3 were used for the preferential CO oxidation (PROX) reaction, which is a highly exothermic reaction requiring high heat flux. For comparison, commercially available α-Al 2 O 3 and γ-Al 2 O 3 were also used as catalyst supports. The catalysts were characterized by N 2 -physisorption, X-ray diffraction, CO chemisorption, transmission electron microscopy (TEM), temperature-programmed desorption of ethanol (ethanol-TPD) and ammonia (NH 3 -TPD), and temperature-programmed oxidation (TPO). The Ru/α-Al 2 O 3 catalyst with the lowest Ru dispersion showed the best PROX performance among the tested catalysts in the absence of CO 2 and H 2 O. Even though Ru/Al@γ-Al 2 O 3 and Ru/γ-Al 2 O 3 had similar Ru dispersions, the former catalyst exhibited a much better PROX performance than the latter. This could be explained by the fact that the Ru metal deposited on Al@γ-Al 2 O 3 was more resistant to surface oxidation as compared to that on γ-Al 2 O 3 , based on the TPO results. A lower desorption temperature of ethanol was observed over Al@γ-Al 2 O 3 than over γ-Al 2 O 3 during ethanol-TPD experiments, even though both supports had similar amounts of acid sites, as determined by NH 3 -TPD. Among the tested catalysts, Ru/Al@γ-Al 2 O 3 also showed the best PROX performance in the presence of CO 2 and H 2 O. A further enhancement in the PROX performance was achieved by increasing the Ru metal particle size from 1.4 to 2.6 nm by pretreating the Ru/Al@γ-Al 2 O 3 catalyst with 1 mol% O 2 in He at 150 ℃. [ABSTRACT FROM AUTHOR]

• Co-pyrolysis of cellulose and LLDPE over MgO catalysts was performed. • MgO catalysts with different surface area and acid/base properties were used. • MgO/C has largest surface area and adequate acid-base property. • MgO/C produced the largest amounts of aromatics. Various MgO impregnated catalysts were used for the catalytic co-pyrolysis (CCP) of cellulose and linear low-density polyethylene (LLDPE) at 600 °C in ambient pressure. Micro reactor-gas chromatography, a semi-batch reactor, was used as a reactor and gas chromatogram/mass spectrometry/flame ionization detector were used for product detection. Three kinds of MgO impregnated catalysts, MgO/Carbon (MgO/C), MgO/Al 2 O 3 , and MgO/ZrO 2 , were prepared by the impregnation of MgO to different supporting material s, C, Al 2 O 3 , and ZrO 2 , respectively. Activities of the three MgO-impregnated catalysts were compared with 1:5 of feedstock to catalyst ratio. MgO/C produced the highest quality oil, which consisted of a large amount of aromatic hydrocarbons during the catalytic pyrolysis (CP) of cellulose. When the MgO catalysts were applied to CCP, the selectivity to aromatic hydrocarbons over MgO/C were 13.42%, which were also much higher than those over the other catalysts, including bulk MgO, demonstrating the effectiveness of the MgO/C catalyst on aromatics formation. Importantly, the experimental BTEXs (benzene, toluene, ethylbenzene, xylenes) yields of CCP over MgO/C were also much higher than the theoretical yields, highlighting the effectiveness of hydrogen-rich LLDPE on the CP of cellulose over MgO/C. Further investigation of the cellulose/LLDPE mixing ratio showed that the amount of BTEXs during the CCP of cellulose and LLDPE could be maximized by adjusting the cellulose to LLDPE mixing ratio to 25:75. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new core@shell catalyst is developed for partial methane oxidation. • SiO 2 @V 2 O 5 @Al 2 O 3 nanostructure is an efficient and thermally stable catalyst. • The thickness of Al 2 O 3 shells over SiO 2 @V 2 O 5 cores can be controlled. • SiO 2 @V 2 O 5 @Al 2 O 3 -(50) nanostructures feature the best catalytic activity at 600 °C. • A highly disperse vanadium species is formed. Abstract The stable tetrahedral geometry and high C H bond dissociation energy of methane complicate its direct catalytic conversion; for example, the selective oxidation of methane to formaldehyde, which avoids the production of carbon dioxide by full oxidation and is therefore important for the versatile utilization of natural gas, is still viewed as challenging. Here, we utilize hydrothermal synthesis followed by atomic layer deposition (ALD) to prepare an efficient and thermally stable catalyst based on novel SiO 2 @V 2 O 5 @Al 2 O 3 core@shell nanostructures, showing that the thickness of Al 2 O 3 shells over SiO 2 @V 2 O 5 cores can be tuned by controlling the number of ALD cycles. Catalytic methane oxidation experiments performed in a flow reactor at 600 °C demonstrate that SiO 2 @V 2 O 5 @Al 2 O 3 nanostructures obtained after 50 ALD cycles exhibit the best catalytic activity (methane conversion = 22.2%; formaldehyde selectivity = 57.8%) and outperform all previously reported vanadium-based catalysts at 600 °C. The prepared catalysts are subjected to in-depth characterization, which reveals that their Al 2 O 3 shell provides new surfaces for the generation of highly disperse T d monomeric species with a V O Al bond by promoting interactions between Al 2 O 3 and V 2 O 5 nanoparticles during ALD. Moreover, the surface Al 2 O 3 shell is found not only to protect V 2 O 5 nanoparticles against sintering at 600 °C, but also to anchor the produced T d monomeric vanadium species responsible for the high catalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A single-step preparation of 2D nickel silicates with delaminated MWW layers. • Hydrothermal conversion of borosilicate MWW precursor with nickel nitrate solution. • In-situ formation of highly dispersed metallic nickel in the external MWW layers. • Unprecedented activity and stability for dry reforming of methane. • A platform technique for synthesis of metal, metal oxide, and acid/base catalysts. Two-dimensional (2D) molecular sieves with highly dispersed nickel species are attractive catalysts for the dry reforming of methane (DRM) because of the ease of molecular diffusion and the deactivation resistance by coke deposition. Here we report the single-step preparation of a 2D nickel silicate molecular sieve with delaminated MWW layers (Ni-DML) by the simple hydrothermal conversion of a borosilicate MWW precursor with nickel nitrate solution. More than 20 wt.% of nickel species were well dispersed in the framework of Ni-DML and the lowest stabilization energy of nickel cluster was calculated using density functional theory calculations. Ni-DML exhibited extremely high conversions of CH 4 and CO 2 as well as an extraordinary stability, maintaining its activity for 10 days on stream due to the in-situ formation of metallic nickel clusters from the framework species. Ni-DML can be used as a catalyst for DRM without pretreatments such as air calcination and H 2 reduction. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical corrosion of carbon in a membrane electrode assembly (MEA) is a critical issue to be resolved to satisfy the durability targets for commercialization of proton exchange membrane (PEM) fuel cells. In order to understand the dominant mechanisms of MEA degradation by carbon corrosion, accelerated stress tests (ASTs), which consisted of holding at 1.3V for 50h, were conducted in a single cell, and the microstructural changes of the cathode catalyst layers (CCLs) and polarization losses were analyzed. The results of carbon corrosion were an increase in CCL porosity and 50% loss in the surface area of the Pt, leading to a 70% loss of the initial MEA performance at 0.6V. Quantitative analyses of polarization losses for the MEA showed that oxygen diffusion was reduced significantly, while there were somewhat smaller increase of the kinetic and high frequency resistance (HFR) losses after carbon corrosion. Carbon oxide species that form on carbon particles during the carbon corrosion process make the surfaces of the CCLs more hydrophilic, and this is believed to diminish oxygen diffusion through the water-filled pores of the CCLs, leading to dramatic degradation of the fuel cell performance. However, another proposed mechanism of diffusion loss, which involves structural collapse and the loss of porosity in the CCLs due to carbon corrosion did not occur in the present study. These findings are anticipated to contribute to the development of more durable MEAs for PEM fuel cells. [Copyright &y& Elsevier]

• CH 4 ex-situ decomposition supplied large amounts of H 2 than CH 4 or N 2 environment. • The 10Ni/5La 2 O 3 -5CeO 2 -Al 2 O 3 catalyst was used for CH 4 decomposition at 800 °C. • Yellow poplar vapors were upgraded over 1 wt% Ga/HZSM-5. • CH 4 ex-situ decomposition enhanced aromatics yield than CH 4 or N 2 environment. • CH 4 ex-situ decomposition can replace expensive reduction process of Ga/HZSM-5. The present study examined the effects of the pyrolysis environment on BTEX (benzene, toluene, ethylbenzene, and xylenes) production in the catalytic upgrading of yellow poplar pyrolysis vapors. Three different gas environments, N 2 , CH 4 , and pre-decomposed CH 4 stream (10 wt%-Ni/5 wt%-La 2 O 3 -5 wt% CeO 2 -Al 2 O 3), which is a mixture of H 2 (55.62%) and CH 4 , were studied using two types of zeolite catalysts, HZSM-5, and 1 wt% Ga/HZSM-5. The BTEX yields were enhanced linearly in the order N 2 < CH 4 < CH 4 ex-situ decomposition. The highest BTEX yield of 9.58 wt% was obtained under the CH 4 ex-situ decomposition environment over 1 wt% Ga/HZSM-5. The methane and hydrocarbons derived from biomass were activated on highly dispersed (GaO)+ sites and transformed smoothly to BTEX by aromatization on the BrØnsted acid sites of Ga/HZSM-5. The hydrogen produced from methane decomposition also assisted in aromatics production through the hydrodeoxygenation of methoxyphenols, guaiacols and catechols. [ABSTRACT FROM AUTHOR]