Carbon Deposition Rate Research Articles

Investigation of La0.6Sr0.4Co1-xNixO3-δ (x=0, 0.2, 0.4, 0.6, 0.8) catalysts on solid oxide fuel cells anode for biogas dry reforming

The introduction of catalyst on anode of solid oxide fuel cell (SOFC) has been an effective way to alleviate the carbon deposition when utilizing biogas as the fuel. A series of La0.6Sr0.4Co1-xNixO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8) oxides are synthesized by sol-gel method and used as catalysts precursors for biogas dry reforming. The phase structure of La0.6Sr0.4Co1-xNixO3-δ oxides before and after reduction are characterized by X-ray diffraction (XRD). The texture properties, carbon deposition, CH4 and CO2 conversion rate of La0.6Sr0.4Co1-xNixO3-δ catalysts are evaluated and compared. The peak power density of 739 mW cm−2 is obtained by a commercial SOFC with La0.6Sr0.4Co0.4Ni0.6O3-δ catalyst at 850 °C when using a mixture of CH4: CO2 = 2:1 as fuel. This shows a great improvement from the cell without catalyst for internal dry reforming, which is attributed to the formation of NiCo alloy active species after reduction in H2 atmosphere. The results indicate the benefits of inhibiting the carbon deposition on Ni-based anode through introducing the La0.6Sr0.4Co0.4Ni0.6O3-δ catalyst precursor. Additionally, the dry reforming technology will also help to convert part of the exhaust heat into chemical energy and improve the efficiency of SOFC system with biogas fuel.

High Fuel Yields, Solar‐to‐Fuel Efficiency, and Excellent Durability Achieved for Confined NiCo Alloy Nanoparticles Using MgO Overlayers for Photothermocatalytic CO2 Reduction

Solar‐energy‐driven CO2 reduction to produce fuel is of great importance for alleviating the greenhouse effect and energy shortage. Here, a composite of MgO overlayers confined NiCo alloy nanoparticles supported on MgO (NiCo@MgO/MgO) is prepared. Extremely high production rates of H2 (rH2) and CO (rCO) (112.98 and 127.13 mmol min−1 g−1, respectively) and large solar‐to‐fuel efficiency (η, 39.3%) are achieved on NiCo@MgO/MgO for photothermocatalytic CO2 reduction by CH4 under ultraviolet–visible–infrared (UV–VIS–IR) illumination. The high fuel production rates and η originate from efficient light–thermal conversion and photoactivation, which can boost the photothermocatalytic activity by reducing the activation energy. Importantly, NiCo@MgO/MgO does not show deactivation during a 90 h photothermocatalytic CO2 reduction by the CH4 durability test, owing to its low carbon deposition rate. Experimental evidence reveals that the NiCo alloy and MgO overlayers can inhibit CO disproportionation and accelerate the oxidation of carbon species, thereby significantly decreasing the carbon deposition rate.

Butadiene production in membrane reactors: A techno-economic analysis

The direct dehydrogenation of butane (BDH) is emerging as an attractive on-purpose technology for the direct production of 1,3-butadine. However, its product yield is hindered by the high rate of carbon deposition associated to the high temperature required for the highly endothermic reaction. In this work, we evaluated the use of H2-selective membrane reactor, to increase the yield of the dehydrogenation process at milder operating conditions. The novel proposed membrane reactor (MR)-assisted BDH technology is compared from a techno-economic point of view with the benchmark technology. The results of this analysis reveal that the MR technology enables to work at milder operating temperatures (−85 °C), reducing carbon formation (−98.5%) and reactor duty (−10%). Due to the higher reaction yields, the MR-assisted BDH technology can lower the required shale gas-based feedstock, maintaining same production capacity as in the benchmark; this will result in an overall plant efficiency of 50.92% in the MR-assisted plant, compared to 37.7% of the benchmark case. This work demonstrates that MR-assisted technology is a valuable alternative to the conventional BDH technology, reducing of almost 20% the final cost of production of 1,3-butadiene, due to the lower installation costs and the higher energy efficiency.

Seep dynamics as revealed by authigenic carbonates from the eastern Qiongdongnan Basin, South China Sea

Methane-related authigenic carbonates play a significant role in the marine carbon cycle and atmospheric CH4 budget. To elucidate the relationship between seeping methane and authigenic carbonate precipitation, we analyze a 72-cm long methane-related carbonate column from the W08 site in the Qiongdongnan Basin, South China Sea. Mineralogical composition, stable carbon and oxygen isotopes, major and trace element contents, and three-dimensional internal structure have been analyzed.Based on the results obtained, four types of carbonate are identified. The first type recorded decreasing content of rare earth elements plus yttrium (REEY) and increasing carbonate porosity. This is attributed to the gradual increase in methane flux intensity, raising the rate of carbonate deposition and thus reducing the time for elemental uptake. The second type of carbonate displays the same δ18O values as the theoretical equilibrium results, the maximum REEY contents, and the densely cemented carbonate structure, indicating a reduction in gas hydrate decomposition. The third type of carbonate formation occurring at the sediment-water interface shows a synchronous and significant enrichment of Mo, V, and Cd contents, suggesting the high hydrogen sulfide flux, which is subject to intensive methane flux and sulfate reduction. The fourth type is the late infill aragonite, which exhibits lower elemental contents compared to early cement due to less exposure to host sediments, while the difference in δ18O and δ13C values is not significant. The compilation of (Tb/Yb)N and Y/Ho ratios of cold-seep carbonates worldwide suggests that the methane flux could alter the space of redox zones (e.g. Fe reduction zone) and thus affect the sink of MREE.X-ray computed tomography (CT) reveals the internal structure of the methane-related carbonate. The continuous pore system probably suggests an intense fluid/gas pressure, and the in situ brecciations imply the carbonate precipitation did not entirely block the methane release to the water column. A better understanding of authigenic carbonates is fundamental to evaluating how carbonates modulate the carbon balance in the methane seeps.

Dry Reforming of Methane on NiCu and NiPd Model Systems: Optimization of Carbon Chemistry

A series of ultra-clean, unsupported Cu-doped and Pd-doped Ni model catalysts was investigated to develop the fundamental concept of metal doping impact on the carbon tolerance and catalytic activity in the dry reforming of methane (DRM). Wet etching with concentrated HNO3 and a subsequent single sputter–anneal cycle resulted in the full removal of an already existing oxidic passivation layer and segregated and/or ambient-deposited surface and bulk impurities to yield ultra-clean Ni substrates. Carbon solubility, support effects, segregation processes, cyclic operation temperatures, and electronic and ensemble effects were all found to play a crucial role in the catalytic activity and stability of these systems, as verified by X-ray photoelectron spectroscopy (XPS) surface and bulk characterization. Minor Cu promotion showed the almost complete suppression of coking with a moderate reduction in catalytic activity, while high Cu loadings facilitated carbon growth alongside severe catalytic deactivation. The improved carbon resistance stems from an increased CH4 dissociation barrier, decreased carbon solubility in the bulk, good prevailing CO2 activation properties and enhanced CO desorption. Cyclic DRM operation on surfaces with Cu content that is too high leads to impaired carbon oxidation kinetics by CO2 and causes irreversible carbon deposition. Thus, an optimal and stable NiCu composition was found in the region of 70–90 atomic % Ni, which allows an appropriate high syngas production rate to be retained alongside a total coking suppression during DRM. In contrast, the more Cu-rich NiCu systems showed a limited stability under reaction conditions, leading to undesired surface and bulk segregation processes of Cu. The much higher carbon deposition rate and solubility of unsupported NiPd and Pd model catalysts results in severe carbon deposition and catalytic deactivation. To achieve enhanced carbon conversion and de-coking, an active metal oxide boundary is required, allowing for the increased clean-off of re-segregated carbon via the inverse Boudouard reaction. The carbon bulk diffusion on the investigated systems depends strongly on the composition and decreases in the following order: Pd > NiPd > Ni > NiCu > Cu.

Mesoporous Gamma‐Alumina‐Supported Mo Catalysts: Effect of Calcination Temperature

AbstractMesoporous γ‐Al2O3‐supported Mo oxides precursors were prepared by one‐step hydrolysis method without organic template at different calcination temperatures (MoOx/γ‐MA‐T) from 400 to 700 °C. Then MoS2 catalysts (MoS2/γ‐MA‐T) were obtained from the precursors through in‐situ sulfurization and applied for hydrodesulfurization (HDS) of dibenzothiophene (DBT). Effects of precursors calcination temperature on physicochemical properties and catalytic performances of catalysts were systematically investigated. With the increase of calcination temperature, the strength of metal‐support interactions and slab lengths of MoS2 increased. The slab stacks were inhibited by the strengthened strong interaction, leading to the reduction of edge/rim sites ratio that are favour for the HDS reaction. Appropriate calcination temperature (500 °C) could make the MoS2/γ‐MA‐500 possess favourable pore structure, particle dispersion, and edge/rim sites ratio, which were conducive to the mass transfer process of reactants and products, and lowered the carbon deposition rate, thus improving its catalytic activity, stability and direct hydrogenolysis desulfurization selectivity.

Bifunctional metal-free KAUST Catalysis Center 1 (KCC-1) as highly active catalyst for syngas production via methane partial oxidation

The metal-free KAUST Catalysis Center 1 (KCC-1) was synthesized through microemulsion method with microwave assistance and was assessed for methane partial oxidation (MPO) under various operating conditions. The electronic spin resonance spectroscopy, pyridine-probed infrared spectroscopy, and temperature-programmed desorption of oxygen measurement indicated that the concentration of BrØnsted acid sites and oxygen vacancies in KCC-1 were at least 2-fold higher than its counterparts, which benefited MPO activity via the promotion of adsorption and dissociation of gaseous reactants. The principal species detected by post-reaction X-ray photoelectron spectroscopy (XPS) was surface-adsorbed oxygen species; its relative percentages among all oxygen species reduced in the order spent KCC-1 (77.1%) > spent MCM-41 (Mobil Composition of Matter number 41; 41.4%) > spent SiO2 (−). The catalytic performance followed the same trend, suggesting that the surface-adsorbed oxygen species was the key factor for MPO process. Additionally, the carbon deposition rate increased in the order SiO2 (16.8 mol/gcat/s) > MCM-41 (11.7 mol/gcat/s) > KCC-1 (7.7 mol/gcat/s), consistent with the results of post-reaction Raman measurements. By coupling the in situ Fourier-transform infrared and XPS results, it is suggested that the high concentration of oxygen vacancies in KCC-1 contributed to activate the CH4 molecules on acid sites via different O∗-assisted kinetically relevant C–H bond activation mechanism for combustion-reforming pathway; meanwhile it provided an excellent adsorption-desorption cycle of O2− species to inhibit the carbon deposition, thus creating a bifunctional reaction mechanism in MPO reaction.

Highly efficient solar-driven CO2-to-fuel conversion assisted by CH4 over NiCo-ZIF derived catalysts

Solar-driven CO2 reduction by CH4 is promising to simultaneously tackle energy shortage and global warming problems by converting two greenhouse gases into fuels. However, serious challenges remain, such as limited light-to-fuel efficiency, high operating temperature, and severe catalyst deactivation. Here, high-performance direct solar-driven CO2 reduction is demonstrated at relatively low operation temperature (594 °C) based on NiCo-ZIF derived nanostructures. An ultrahigh light-to-fuel efficiency of 32.4% and production rates of H2 (105.83 min−1g−1) and CO (128.17 mmol min−1g−1) are achieved via photothermocatalysis on Ni1Co2@CZIF-Al2O3 catalysts. Excellent light-to-fuel conversion performance can be attributed to the highly dispersed metal particles, decreased apparent activation energy under direct light illumination, increased CO2 absorption, and promoted dissociation of CH4 to CH3* of NiCo alloy. The carbon deposition rate of NiCo bimetallic catalysts is prominently inhibited compared with pure Ni or Co catalysts due to the change of the reaction path, as confirmed by DFT calculations. This work opens new routes to achieve highly efficient solar-driven CO2 reduction by CH4 based on NiCo-ZIF derived alloy nanostructures at relatively low-temperature conditions.

A Green and Cost-Effective Synthesis of Hierarchical SAPO-34 through Dry Gel Conversion and Its Performance in a Methanol-to-Olefin Reaction

In this work, a low-cost and high-performance methanol-to-olefin (MTO) catalyst was synthesized by dry gel conversion (DGC). Using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) to prepare the dry gel, nano-SAPO-34 in a range of 50–500 nm was synthesized under the effect of the vapor of triethylamine (TEA) and H2O. The TEAOH consumption using this method was only 7.5% of that in the hydrothermal synthesis (HTS), and the yield of nano-SAPO-34 products was up to 94%. When scaling up to the pilot test, obvious heterocrystals appeared with the decrease in SiO2 content in the dry gel. Our results showed that the heterocrystals were completely eliminated after the introduction of fluoride into the dry gel. A low acid density nanosheet-SAPO-34 molecular sieve product with good micropore, mesopore, and macropore connectivity was obtained. The obtained multikilogram-scale molecular sieve sample can be directly shaped to obtain MTO microsphere catalysts by spray drying without separation and washing. No wastewater was produced during the whole process, demonstrating an entirely green production way. The MTO performance of the microsphere catalysts was tested in a fluidized bed reactor, and results showed that the catalysts exhibited the characteristics of a slow carbon deposition rate and a high activity utilization ratio. Their lifetime was extended by 14%, and their selectivity (C2= + C3=) was increased by 1.55%, so they are very suitable for industrial application. This work has provided the theoretical and practical basis for the industrial production and application of DGC in the future.

Facile and Rapid Synthesis of Durable SSZ-13 Catalyst Using Choline Chloride Template for Methanol-to-Olefins Reaction

In the current study, a facile and rapid synthesis approach for a SSZ-13 catalyst using choline chloride (CC) as a template was proposed, and the catalytic performance for the methanol-to-olefins (MTO) reaction was examined. With a proper amount of CC addition (i.e., m(CC)/m(SiO2) = 0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained within 4 h with lower aggregation. The synthesized catalyst demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.71 m2·g−1 and 0.04 cm3·g−1, respectively. The optimized strong and weak acid sites on SSZ-13 were obtained by regulating the m(CC)/m(SiO2) ratio. The less strong acid sites and a larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance of the MTO reaction under a lower reaction temperature (450 °C). The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could also slow down the carbon deposition rate and, thus, significantly improve the catalytic lifetime of the catalyst. The methanol conversion rate and initial selectivity of light olefin using the synthesized catalyst could maintain over 95% and 50%, respectively, and a lifetime of 172 min was achieved. Although the low olefin selectivity of the synthesized SSZ-13 catalyst was slightly lower than that of the purchased one, its desirable features were thought to have good potential for industrial application.

An Experimental Performance Study of a Catalytic Membrane Reactor for Ethanol Steam Reforming over a Metal Honeycomb Catalyst.

The present study deals with the combination of ethanol steam reforming over a monolithic catalyst and hydrogen separation by membrane in a lab-scale catalytic membrane reactor (CMR). The catalyst was comprised of honeycomb thin-walled Fechralloy substrate loaded with Ni + Ru/Pr0.35Ce0.35Zr0.35O2 active component. The asymmetric supported membrane consisted of a thin Ni-Cu alloy–Nd tungstate nanocomposite dense permselective layer deposited on a hierarchically structured asymmetric support. It has been shown that the monolithic catalyst-assisted CMR is capable of increasing the driving potential for hydrogen permeation through the same membrane as compared with that of the packed bed catalyst by increasing the retentate hydrogen concentration. Important operating parameters responsible for the low carbon deposition rate as well as the amount of hydrogen produced from 1 mol of ethanol, such as the temperature range of 700–900 °C, the water/ethanol molar ratio of 4 in the feed, have been determined. Regarding the choice of the reagent concentration (ethanol and steam in Ar), its magnitude may directly interfere with the effectiveness of the reaction-separation process in the CMR.

Photothermocatalytic CO2 Reduction on Magnesium Oxide‐Cluster‐Modified Ni Nanoparticles with High Fuel Production Rate, Large Light‐to‐Fuel Efficiency and Excellent Durability

Highly efficient CO2 reduction to produce fuel driven by solar energy is of great significance to alleviate the greenhouse effect and realize solar energy storage. Herein, a unique nanocomposite of MgO‐cluster‐modified Ni nanoparticles supported on Ni‐doped MgO (MCM–Ni/Ni–MgO) is synthetized by a simple approach. Very high fuel production rate for H2 and CO (78.01 and 88.44 mmol min−1 g−1) as well as a large light‐to‐fuel efficiency (31.7%) are achieved by photothermocatalytic CO2 reduction by CH4 on MCM–Ni/Ni–MgO merely using focused UV–vis–IR illumination. This arises from efficient light‐driven thermocatalysis that is further enhanced by a photoactivation due to the activation energy being considerably reduced upon the illumination. More importantly, it exhibits excellent photothermocatalytic durability due to its extremely low carbon deposition rate of 8.85 × 10−4 gc h−1 g−1 catalyst, reduced by 39.2 times as compared with that of a reference sample of Ni nanoparticles supported on Ni‐doped MgO (Ni/Ni–MgO). The experimental evidences and the functional theory calculations reveal that the surface modification of Ni nanoparticles by MgO cluster not only inhibits the carbon deposition side reactions of CO disproportionation and CH4 complete dissociation, but also significantly accelerates the oxidation of carbon species, thus tremendously decreasing carbon deposition rate.

Micro-trench measurements of the net deposition of carbon impurity ions in the DIII-D divertor and the resulting suppression of surface erosion

We report carbon impurity ion incident angles and deposition rates, along with silicon erosion rates, from measurements of micro-engineered trenches on a silicon surface exposed to L-mode deuterium plasmas at the DIII-D divertor. Post exposure ex-situ analysis determined elemental maps and concentrations, carbon deposition thicknesses, and erosion of silicon surfaces. Carbon deposition profiles on the trench floor showed carbon ion shadowing that was consistent with ERO calculations of average carbon ion angle distributions (IADs) for both polar and azimuthal angles. Measured silicon net erosion rates negatively correlated with the deposited carbon concentration at different locations. Differential erosion of surfaces on two different ion-downstream trench slope structures suggested that carbon deposition rate is affected by the carbon ion incident angle and significantly suppressed the surface erosion. The results suggest the C impurity ion incident angles, determined by the IADs and surface morphology, strongly affect erosion rates as well as the main ion (D, T, He) incident angles.

Hemispheric black carbon increase after the 13th-century Māori arrival in New Zealand.

New Zealand was among the last habitable places on earth to be colonized by humans1. Charcoal records indicate that wildfires were rare prior to colonization and widespread following the 13th- to 14th-century Māori settlement2, but the precise timing and magnitude of associated biomass-burning emissions are unknown1,3, as are effects on light-absorbing black carbon aerosol concentrations over the pristine Southern Ocean and Antarctica4. Here we used an array of well-dated Antarctic ice-core records to show that while black carbon deposition rates were stable over continental Antarctica during thepast two millennia, they were approximately threefold higher over the northern Antarctic Peninsula during the past 700 years. Aerosol modelling5 demonstrates that the observed deposition could result only from increased emissions poleward of 40°S-implicating fires in Tasmania, New Zealand and Patagonia-but only New Zealand palaeofire records indicate coincident increases. Rapid deposition increases started in 1297 (±30 s.d.) in the northern Antarctic Peninsula, consistent with the late 13th-century Māori settlement and New Zealand black carbon emissions of 36 (±21 2s.d.) Gg y-1 during peak deposition in the 16th century. While charcoal and pollen records suggest earlier, climate-modulated burning in Tasmania and southern Patagonia6,7, deposition in Antarctica shows that black carbon emissions from burning in New Zealand dwarfed other preindustrial emissions in these regionsduring the past 2,000 years, providing clear evidence of large-scale environmental effects associated with early human activities across the remote Southern Hemisphere.

One-pot synthesis of [Mn,H]ZSM-5 and the role of Mn in methanol-to-propylene reaction

A Mn-modified ZSM-5 zeolite (Mn-HZ) was synthesized using a quasi-solid-phase method, and its physicochemical properties were characterized. The presence of tetracoordinated framework Mn(III) was confirmed using ultraviolet–visible and Raman spectroscopy measurements, X-ray photoelectron spectroscopy, and H2-temperature programmed reduction, and the results suggest that Mn entered the framework structure of ZSM-5. Crucially, the introduction of Mn increased the weak Brønsted acid site content and decreased the strong acid site content and resulted in an increase in the amount of framework Al in the straight zeolite channels. During application for the methanol-to-propylene reaction (MTP), Mn-HZ produced fewer aromatics and had a lower carbon deposition rate than the unmodified zeolite, resulting in a longer catalyst lifetime and higher selectivity for propylene and butene. In addition, a mechanism for the MTP reaction is proposed based on the detection of ethylene in high concentrations in the initial stages of the reaction, suggesting that it could be the initial hydrocarbon pool species. Overall, our results indicate that Mn-HZ favored the olefin-based cyclic mechanism to the aromatic-based mechanism.

Well-Dispersed MgAl2O4 Supported Ni Catalyst with Enhanced Catalytic Performance and the Reason of Its Deactivation for Long-Term Dry Methanation Reaction

Dry methanation of syngas is a promising route for synthetic natural gas production because of its water and cost saving characteristics, as we reported previously. Here, we report a simple soaking process for the preparation of well-dispersed Ni/MgAl2O4-E catalyst with an average Ni size of 6.4 nm. The catalytic test results showed that the Ni/MgAl2O4-E catalyst exhibited considerably higher activity and better stability than Ni/MgAl2O4-W catalyst prepared by conventional incipient wetness impregnation method in dry methanation reaction. The long-term stability test result of 335 h has demonstrated that the deactivation of the Ni/MgAl2O4-E catalyst is inevitable. With multiple characterization techniques including ICP, EDS, XRD, STEM, TEM, SEM and TG, we reveal that the graphitic carbon encapsulating Ni nanoparticles are the major reasons responsible for catalyst deactivation, and the rate of carbon deposition decreases with reaction time.

Dry methane reforming with nickel–cobalt bimetallic catalysts based on halloysite nanoclay modified by alkaline melting method

AbstractCatalysts, including (10% Ni)/AMHA, (10% Ni + 5% Co)/AMHA, (5% Ni + 5% Co)/AMHA, and (5% Ni + 10% Co)/AMHA, were prepared by simultaneous impregnation of Ni and Co on alkaline molten halloysite (AMHA) and characterized by X‐ray diffraction (XRD), field diffusion scanning electron microscopy (FESEM), temperature‐programmed reduction (TPR), temperature‐programmed oxidation (TPO), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), atomic force microscopy (AFM), and Brunauer–Emmett–Teller (BET). The catalysts were evaluated in dry reforming of methane (DRM) at temperatures of 700 to 850°C and with a volumetric composition of a feed gas of 40% CH4, 40% CO2, and 20% Ar in a fixed bed reactor. Catalyst performance tests showed that the nickel catalyst based on milled and alkaline molten nano‐halloysite had a relatively poor performance. After impregnation of cobalt metal with different concentrations in the presence of nickel, the functional properties increased. Characteristic observations and experiments showed a very positive effect of cobalt metal on the catalyst performance. The presence of cobalt reinforcing metal along with nickel improves the activity and stability and reduces catalyst coking. Moreover, increasing cobalt along with nickel leads to better dispersion of the active phase of nickel, improved catalyst regeneration, and stable production of synthetic gas from methane and carbon dioxide. The effect of cobalt and nickel ratio on the catalyst structure, conversion rate of methane and carbon dioxide, stability, and carbon deposition rate were investigated. The conversion rate increases at high temperatures. Also, the resulting gas composition is suitable for Fischer–Tropsch reactions.

Solar‐Enhanced CO2 Conversion with CH4 over Synergetic NiCo Alloy Catalysts with Light‐to‐Fuel Efficiency of 33.8%

CO2 conversion In article number 2100185, Yimin Xuan and co-workers introduced NiCo alloys derived from AlMg hydrotalcite for photothermal synergetic CO2 conversion with CH4 with ultrahigh light-to-fuel efficiency of 33.8% and low carbon deposition rate. The ultrahigh efficiency is attributed to the high solar absorptance of NiCo alloys, the unique synergistic catalysis of NiCo active sites, and the photo-enhanced reactant activation.

First-Principles Calculation and Multi-Scale Observation for a Carbon Deposition on a SOFC Anode Near the Interface

The nickel/yttria-stabilized zirconia (Ni/YSZ) and nickel/scandia-stabilized zirconia (Ni/ScSZ) have widely used as an anode for solid oxide fuel cells (SOFCs). The high operation temperature allows an SOFC to operate on a wide range of fuels, including hydrocarbons and coal syngas. Ni is also a catalyst for carbon deposition reactions which destroy the anode microstructure. Meanwhile, the carbon deposited on the electrode can be used for different ways. It is important to control the carbon deposition on the electrode; therefore, the carbon deposition model needs to be developed.In this study, carbon deposition site in the Ni/YSZ and Ni/ScSZ was studied through first-principles calculation and multi-scale observation using SEM and TEM. Observation showed that the carbon deposition was progressed not in the overall Ni surface but in the specific sites such as the interfaces and Ni(211) facet at low temperature. The carbon deposition rate strongly depended on the electrode structure at microscales. All calculations here are performed employing the periodic density functional theory (DFT) method implemented in the Vienna Ab-Initio Simulation Package (VASP). The Ni/YSZ and Ni/ScSZ atomic models are developed to discuss the CH adsorption which is the initial step of the carbon deposition. The CH adsorption energy in the concentrated vacancies at the Ni/YSZ interface was much lower than that in the Ni(111) facet, indicating that concentrated vacancies become the active site of the carbon deposition. However, the CH adsorption energy in the dispersed vacancies are almost the same as that in the Ni(111) facet. It is shown that vacancy patterns play an important role in the carbon deposition rate. The impact of dopant in the anode on the carbon deposition is also studied. DFT calculation gives an useful hint to develop the carbon deposition model with considering the electrode structure.

Surface Analyses of adsorbed and deposited species on the Ni-Mo catalysts surfaces after Guaiacol HDO. Influence of the alumina and SBA-15 supports.

• Raman identified aromatic and oxygenated organic compounds on alumina-supported catalyst. • FTIR showed carbon deposits on the SBA-15 as aliphatic simple molecules. • Carbon deposited on the NiMo/SBA-15 catalyst were light polymer types. • Alumina catalyst formed mainly carbon species graphite type and heavier carbons. • The deactivation was 44% higher for the NiMo/Al2O3 than for SBA-15 We studied and identified compounds adsorbed or deposited on the catalysts surface of the Ni-Mo supported on alumina and SBA-15, before and after hydrodeoxigenation of a bio-oil model (guaiacol). Marked differences were observed on both catalysts through DRIFTS and Raman spectroscopy showing that the alumina-supported catalyst contains deposits of aromatic and oxygenated organic substances, while the carbon deposits on the SBA-15 as aliphatic simple molecules. TPO analyses confirm that the carbon deposited on the NiMo/SBA-15 catalyst were light polymer types, mainly nanotubes and nano fibers, while on the alumina catalyst the mainly carbon species formed were graphite type and heavier carbons. Post reaction analysis of the catalysts showed coke formation and carbon deposition rate of 1.14 mg coke .g cat −1 h − 1 for NiMo/SBA-15 and the deactivation was 44% higher for the NiMo/Al 2 O 3 with 1.65 mg coke .g cat −1 h − 1 of carbon deposition rate.