Carbon Deposition Rate Research Articles

Insights into the effect of Fe-Zn interaction on tunable reactivity in Fischer–Tropsch synthesis

In the Fischer–Tropsch synthesis (FTS) reaction, the intricate reaction conditions are prone to induce phase transitions in iron carbides, which markedly affect catalytic performance. Manipulating and stabilizing the active phase is paramount for ensuring the catalyst efficiency. In this study, we regulated the Fe-Zn interaction to investigate the influence of iron carbides and the characteristics of surface carbon species. The strong interaction significantly enhanced the adsorption and dissociation of CO on the catalyst surface, thereby facilitating the formation of carbon-rich Fe2(.2)C. Consequently, the FeZn-s catalyst exhibited the highest iron time yield (FTY) of 959 μmolCO·gFe-1·s-1. But meanwhile, the stronger Fe-Zn interaction also accelerated the carbon deposition rate and elevated the graphitization degree of the surface carbon, expediting the catalyst deactivation. These results provide an insight into the modulation and stabilization of iron carbides by adjusting the interaction between the Fe and supports, which inspires the further development of Fe-based catalysts for FTS applications.

Exploring the influence of different precursor materials on the catalytic performance and deactivation characteristics of iron-loaded biochar catalysts for the catalytic cracking of toluene

This study employed rice husks (RH), corn stalks (CS), and camphor leaves (CL) as biomass sources to prepare iron-loaded biochar catalysts, elucidating the key relationships between these biomass materials, their catalytic performance, and their resistance to deactivation in toluene. Experimental results indicated that the carbon deposits in the three spent catalysts are primarily composed of inert carbon (Cγ). The carbon peaks in these deposits primarily consisted of CO, CC, and CO structures, with varying proportions across the different types of spent catalysts. Specifically, the RH spent catalyst exhibited the highest relative content of the CO structure at 13.49 %, the CS spent catalyst showed the highest relative content of the CC structure at 89.19 %, and the CL spent catalyst displayed the highest relative content of the CO structure at 5.57 %. Fe2+ was the predominant species on the surfaces of all three spent catalysts, accounting for over 50 % in each case. Fe3C was detected on the surfaces of the CS and CL spent catalysts but was absent on the RH spent catalyst. After 80 min of reaction, the carbon deposition rate of the CL catalyst was 8.15 %, with a catalytic cracking efficiency of 28.04 %, making it the most effective overall. This effectiveness was attributed to the CL catalyst's highest oxygen vacancy intensity, where the abundant oxygen source effectively promoted the catalytic reaction of toluene and inhibited carbon deposition. After three consecutive regeneration cycles, the catalytic cracking efficiency of the CL catalyst remained above 70 %, demonstrating strong cyclic regeneration performance. This study provides theoretical insights into the effective utilization of agricultural and forestry waste, contributing to environmental protection.

Pressure-Induced Enhancement in Chemical Looping Reforming of CH4: A Thermodynamic Analysis with Fe-Based Oxygen Carriers.

Chemical looping reforming of methane (CLRM) with Fe-based oxygen carriers is widely acknowledged as an environmentally friendly and cost-effective approach for syngas production, however, sintering-caused deactivate of oxygen carriers at elevated temperatures of above 900 °C is a longstanding issue restricting the development of CLRM. Here, in order to reduce the reaction temperature without compromising the chemical-looping CH4 conversion efficiency, we proposed a novel operation scheme of CLRM by manipulating the reaction pressure to shift the equilibrium of CH4 partial oxidation towards the forward direction based on the Le Chatelier's principle. The results from thermodynamic simulations showed that, at a fixed reaction temperature, the reduction in pressure led to the increase in CH4 conversion, H2 and CO selectivity, as well as carbon deposition rate of all investigated oxygen carriers. The pressure-negative CLRM with Fe3O4, Fe2O3 and MgFe2O4 could reduce the reaction temperature to below 700 °C on the premise of a satisfactory CLRM performance. In a comprehensive consideration of the CLRM performance, energy consumption, and CH4 requirement, NiFe2O4 was the Fe-based OCs best available for pressure-negative CLRM, especially for an excellent syngas yield of 23.08 mmol/gOC. This study offered a new strategy to address sintering-caused deactivation of materials in chemical looping from the reaction thermodynamics point of view.

The effect of hydrothermal pretreatment on the catalytic performance of Zn/HZSM-5 catalysts for ethylene aromatization reaction

To address the issue of coking and deactivation of Zn/HZSM-5 catalysts used for lightolefins aromatization, a high-temperature hydrothermalmethod was employed for catalyst pretreatment. The catalysts were characterized using XRD, N2 physical adsorption-desorption, NH3-TPD, Py-FTIR, XPS, and TG techniques. The effect of high-temperaturehydrothermal pretreatment on the catalytic performance and stability of the catalyst was investigated using ethylene aromatization as a probe reaction. The results showed that the Zn/HZSM-5 catalyst exhibited excellent catalytic performance after48 h of high-temperature hydrothermal pretreatment. Although the conversion of ethylene slightly decreased, the catalyst lifetime was significantly extended, increasing from 72to 216 h, while the aromatics selectivity remained above 60%. It was suggested that the hydrothermal treatment enhanced the interaction between ZnO species and Brønsted acid sites, promoting the generation of ZnOH+ species. This not only suppressed the hydrogen transfer reaction but also significantly enhanced the dehydrogenation performance of the catalyst, improving the selectivity towards hydrogen. Additionally, the catalyst exhibited increased carbon capacity and reduced carbon deposition rate after hydrothermal treatment, demonstrating excellent anti-coking properties.

A comprehensive kinetic study on low-GHG hydrogen production from microwave-driven methane pyrolysis

The present study focuses on the cogeneration of hydrogen (H2) and solid carbon from microwave-driven methane pyrolysis in a fluidized bed of carbon pellets. Numerical simulations using a coupled gas-solid chemistry approach reveal that introducing microwave thermal effects improves methane conversion rate, H2 selectivity, and carbon deposition rate. The chemical pathways analysis divulges that once the leading reaction for decomposing CH4 into H2, i.e., CH4+H ↔ CH3+H2, is completed, the C2H2 deposition mechanism onto the carbon pellets is the dominant pathway for the solid carbon production, indicating almost no carbon black (i.e., nanoparticles) formation. Carbon pellets provide abundant surface area for the conversion of C2H2 to H2, enhancing H2 selectivity in the resulting products. More importantly, the importance of more complex molecules, such as polycyclic aromatic hydrocarbons, greatly diminishes when using carbon pellets in the pyrolysis process, implying that smaller kinetic mechanisms are equally effective and desirable.

Exceptional stability of spinel Ni–MgAl2O4 catalyst with ordered mesoporous structure for dry reforming of methane

The dry reforming of methane reaction holds significant importance for the comprehensive utilization of CO2 and CH4, contributing to carbon neutrality. However, due to the high reaction temperatures, catalyst deactivation due to carbon deposition and sintering remains a challenge. In this study, a one-pot method was employed to improve the solvent evaporation self-assembly process for the preparation of Ni–MgAl2O4 catalysts. The impact of calcination temperature (600 °C, 800 °C, and 1000 °C) on the ordered mesoporous structure of the catalyst was investigated. Catalysts without an ordered mesoporous structure, such as Ni–MgAl2O4-1000, suffered deactivation due to carbon deposition caused by the large size of Ni grains, while Ni–MgAl2O4-600 deactivated due to sintering caused by the lack of confinement effect of the support on Ni. Conversely, Ni–MgAl2O4 catalysts with an ordered mesoporous structure exhibited confinement effects on Ni metal, resulting in excellent resistance to carbon deposition and sintering. Further investigation into the effect of different loading methods of Ni on methane dry reforming was conducted. A comparison was made between Ni–MgAl2O4 (800 °C) prepared by the one-pot method and Ni/MgAl2O4 (800 °C) prepared by the impregnation method. It was observed that Ni–MgAl2O4 catalysts, with Ni incorporated into the support, exhibited strong interaction between Ni and the support. During a 500-h long-term reaction, both CO2 and CH4 conversion rates remained at 90% for Ni–MgAl2O4 catalysts, with less carbon deposition and slower grain growth rate, demonstrating excellent reaction activity and stability. In contrast, the performance of Ni/MgAl2O4 catalysts gradually declined after 260 h. Ni–MgAl2O4 catalysts with ordered mesopores and strong interaction between Ni and the support displayed superior resistance to carbon deposition and sintering.

Synergetic effect for highly efficient light-driven CO2 reduction by CH4 on Co/Mg-CoAl2O4 promoted by a photoactivation

The utilization of photothermocatalytic dry reforming of methane is shown to be an up-and-coming technology. However, reaching high fuel productivity at a comparatively low light intensity and effectively suppressing the side reactions of coking in the DRM process are still two tough difficulties. Under focused UV–vis–IR irradiation at a relatively low light intensity of 80.5 kW m−2, a nanostructure of Co/Mg-CoAl2O4 possesses excellent photothermocatalytic activity and a light-to-fuel efficiency of 34.2 % and a low carbon deposition rate compared to its reference catalyst without Mg2+ doping (Co/CoAl2O4). The improved photothermocatalytic activity and coking resistance of Co/Mg-CoAl2O4 mainly comes from the synergetic effect, including Mg2+ doping, the active lattice oxygen in CoAl2O4 also participating in the oxidation of carbon species, and strong light absorption properties of the Mg-CoAl2O4. The photoactivation promotes DRM on Co nanoparticles while significantly facilitates the C* oxidation by strongly adsorbed CO2 on doped Mg2+.

Development of a dynamic gas lock inhibited model for EUV-induced carbon deposition.

The optical surface of extreme ultraviolet (EUV) lithography machines is highly vulnerable to contamination by hydrocarbons, resulting in the formation of carbon deposits that significantly degrade the quality and efficiency of lithography. The dynamic gas lock (DGL) has been proven as an effective approach to alleviate carbon deposition. However, the majority of existing studies on carbon deposition neglect the influence of the DGL. This paper is dedicated to investigating the phenomena of hydrocarbon adsorption, desorption, and cleavage with considering the effects of the DGL. A comprehensive mathematical model of the carbon deposition process is established, and the impact of radiation intensity, temperature, and hydrocarbon types on the depositing rate is considered. The results suggest that the primary cause of carbon deposition is the direct cracking of hydrocarbons induced by photons with a wavelength range between 12.5 and 14.5nm. Additionally, it has been observed that the carbon deposition rate decreases exponentially as clean gas flow increases when EUV radiation intensity exceeds 50 mW/mm2. Conversely, at low EUV radiation intensity, clean gas flow has little effect on the carbon deposition rate. An effective approach to mitigate carbon deposition is to elevate the temperature of the optical surface and employ light hydrocarbon materials in the EUV process.

Dry reforming of methane by La2NiO4 perovskite oxide: B-site substitution improving reactivity and stability

The development of highly active and stable catalyst materials is the focus of dry reforming of methane (DRM) technology. The effect of substituting transition metals (Mn, Fe, Co, and Cu) on the B-site of La2NiO4 perovskite on the DRM catalytic performance was investigated. Compared to the unsubstituted sample, the Co-substituted sample exhibited reduced reactivity but increased carbon deposition; the Mn-substituted and Fe-substituted samples demonstrated decreased reactivity and carbon deposition; the Cu-substituted sample displayed a slight decrease in CH4 conversion but a substantial increase in carbon resistance. The effect of the substitution ratios of Cu elements was further investigated. The results showed that Cu substitution could maintain the perovskite phase in the samples. In the 5-h DRM reaction, the reactivity of the samples exhibited a decreasing trend as Cu substitution ratios increased. All Cu-containing samples displayed carbon deposition rates lower than 0.4 mg/(g*h), resulting in an over 90-fold improvement in carbon resistance compared to the La2NiO4 sample. Further investigations revealed that the La2Ni0.6Cu0.4O4 sample exhibited stable activity during the 50-h DRM reaction with only a small amount of amorphous carbon in the reacted sample (no obvious carbon nanotubes were observed). Characterization results indicated that the enhanced carbon resistance in Cu-substituted samples was attributed to the Ni-Cu alloy formation, which inhibited CH4 decomposition reactions and reduced solid carbon generation rates. Density functional theory (DFT) calculations showed that the partial substitution of Cu could increase the energy barrier of the CH* dehydrogenation step, which in turn reduced the rate of solid carbon generation.

Carbon storage in mollusk shells: An overlooked yet significant carbon sink in terrestrial ecosystems

Mollusks, the second largest animal family, are found in a variety of ecosystems. As they grow, their shells absorb carbon and form calcium carbonate, making them an important storage place for carbon. However, the amount of carbon deposited in the carbonate shells of terrestrial mollusks throughout modern and geological history has not been quantified. In this study, we first conducted an investigation of carbon deposits in shells from various mollusk species at 470 modern surface soil sample sites across diverse terrestrial ecosystems in China. The deciduous broadleaf forest and shrublands exhibited a higher carbon deposition rate of ∼1.37 ± 2.15 and ∼1.56 ± 2.92 g C m−2/yr−1, while croplands and grasslands displayed a rate of ∼1.11 ± 1.95 and 1.07 ± 1.78 g C m−2/yr−1, respectively. Using geostatistical methods, we estimated the total shell carbon deposition of grassland, forest, shrublands, and croplands in China to be ∼3.39–5.45 × 106 t C yr−1, constituting ∼1.68–2.71 % of China's terrestrial carbon sink, an overlooked portion in previous studies. Additionally, we provided quantitative data on shell carbon fluxes spanning a remarkable 20,000-year period through over ten fossil sequences from loess deposits. The results underscore the continuous and abundant carbon deposition in mollusk shells across various locations for at least 20,000 years, highlighting the persistence and substantial accumulation of shell carbon deposits over time. Remarkably, we estimated that the total shell carbon deposition of loess sediments in China and the world over the past 20,000 years may reach 1.10 × 108 t C and 1.29 × 109 t C, roughly equivalent to an afforestation area of 2.32 × 106 km2 and 2.72 × 107 km2, respectively.

Novel-ordered hierarchical ZSM-5 zeolite with interconnected macro–meso–microporosity for the enhanced methanol to aromatics reaction

The methanol to aromatics (MTA) process is an attractive non-petroleum route to produce high-value aromatics but suffers from a high rate of carbon deposition and deactivation and relatively low BTX selectivity.

Effects of molybdenum addition to activated carbon supported Ni‐based catalysts for CO2 methanation

AbstractRecently, CO2 methanation has become a technique that aims to reduce anthropogenic CO2 emissions by converting CO2 captured from stationary and mobile sources and H2 produced from renewable sources into CH4. Due to their excellent performance‐to‐cost ratio, Ni‐based catalysts were frequently used in such conversions. The main drawbacks, however, are that Ni has the propensity to aggregate and deposit carbon during the high‐temperature reaction. These issues can be partially resolved by including a support (e.g., MOF, zeolite, activated carbon, etc.) and a second transition metal (e.g., Mo, Co, or Fe) in Ni‐based catalysts. Therefore, the activity of Ni‐based catalysts at low temperatures needs to be improved. In this study, a series of mesoporous activated carbon (AC) supported bimetallic Ni–Mo catalysts (Ni–xMo/AC, Ni = 13 wt.%, x = 5, 7, 9, 11 wt.%) were synthesized using the incipient wetness impregnation method. The effect of Mo content on the catalyst's activity was examined in a fixed‐bed reactor. At 250–650°C, 1‐atmosphere pressure, gas hourly space velocity (GHSV): 1200 mL h−1 g−1, and H2/CO2 ratio: 4:1, the catalytic efficiency of these catalysts was examined. The catalysts were analyzed using transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), X‐ray powder diffraction (XRD), N2‐physisorption, and scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM‐EDX). Ni–7%Mo/AC catalyst showed the lowest carbon deposition rate, superior stability, and the best activity. The addition of Mo can improve the heat resistance of the Ni/AC catalyst and the interaction between the metal nickel and the support, which prevents the sintering of the catalyst. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Divergent Effects of Topography on Soil Properties and Above-Ground Biomass in Nepal’s Mid-Hill Forests

Various factors, including topography, climate, soil attributes, and vegetation composition, influence above-ground biomass productivity in forest ecosystems. Despite the success of community forestry in restoring degraded hill forests in Nepal, existing research offers limited insights into how topographic factors and plant species affect soil chemical properties and, in turn, influence above-ground biomass. This study investigates the interrelations between altitude, aspect, soil depth, and vegetation type on soil organic carbon (SOC), total nitrogen (TN), available phosphorus (P), available potassium (K), and soil pH. These soil metrics are further correlated with forestry indices, such as diameter at breast height (DBH), tree height (Ht), above-ground tree biomass (AGTB), basal area (BA), and above-ground total carbon (AGTC), in the mid-hill region of central Nepal. Our findings indicate that aspect had a significant influence on SOC (p < 0.001), TN (p < 0.001), P (p < 0.05), and pH (p < 0.001) levels. Soils in the northwest (NW) aspect exhibited higher levels of SOC and TN but lower levels of P and pH than those in the southeast (SE) aspect. Altitude did not significantly affect soil properties. Variations in SOC, TN, K, and pH were observed across different soil depths. Key forestry metrics like DBH, Ht, AGTB, and AGTC were notably higher at elevated altitudes and under the NW aspect. We also found that vegetation composition adds a layer of complexity to the relationship between aspect, soil properties, and above-ground biomass. The higher altitudes in the SE aspect are more conducive to above-ground biomass productivity, while the NW aspect is favorable for higher levels of SOC and TN in the soil. These variations could be due to differences in carbon deposition rates, plant compositions, soil microbial activities, and microclimatic conditions between the aspects. These findings highlight the need for holistic forest management approaches that consider topographic factors, soil depth, and plant species, offering practical implications for the region’s sustainable forest management and restoration efforts.

Three-Dimensional Kinetic Simulations of Carbon Backsputtering in Vacuum Chambers from Ion Thruster Plumes

Gridded ion thrusters are tested in ground vacuum chambers to verify their performance when deployed in space. However, the presence of high background pressure and conductive walls in the chamber leads to facility effects that increase uncertainty in the performance of the thruster in space. To address this issue, this study utilizes a fully kinetic simulation to investigate the facility effects on the thruster plume. The in-chamber condition shows a downstream neutral particle density 100 times larger than the in-space case due to ion neutralization at the wall and limited vacuum pump capability, resulting in a significant difference in the density and distribution of charge-exchange ions. The flux, energy, and angle of charge-exchange ions incident on the chamber wall are found to be altered by the electron sheath, which can only be simulated by the fully kinetic approach, as opposed to the conventionally used quasi-neutral Boltzmann approach. We also examine the effect of backsputtering, another important facility effect, and find that it does not necessarily require a fully kinetic simulation as the incident flux and energy of the sampled charge-exchange ion are negligibly small. Finally, we demonstrate that the carbon deposition rate on the thruster is significantly influenced by the angular dependence of the sputtered carbon, with a nearly 50% effect.

Carbon deposition properties and regeneration performance of La2NiO4 perovskite oxide for dry reforming of methane

One of the key points in the development of dry reforming of methane (DRM) is the design of catalysts with high activity and stability. The reactivity and carbon deposition properties of La2NiO4 in DRM, as well as its regeneration performance, were studied. The results showed that the in-situ decomposition of La2NiO4 led to a more uniform distribution of smaller Ni0 particles on the La2O3 matrix compared with the directly loaded NiO/La2O3. A temperature-programmed test revealed that the breakthrough curve temperature for La2NiO4 in DRM was 618 °C. The carbon deposition would carry Ni0 metal away from the La2O3 matrix, making the solid carbon unable to be removed promptly due to insufficient oxygen supply, resulting in an increase in the catalyst's instantaneous carbon deposition rate at 650 °C and 750 °C. The regeneration tests showed that the samples' DRM performance and carbon deposition levels remained relatively stable before and after steam regeneration. However, air-regenerated samples exhibited a hysteresis time in DRM due to sintering. Additionally, CO2 was unable to completely remove carbon deposition from the samples, resulting in a significant increase in carbon deposition when regenerated samples were used for DRM.

Tuning the surface carbonaceous species in syngas-to-olefin reaction by metal-support interaction: A Fe-Mn-Al ternary system study

Fabrication of active iron carbides is essential for CO dissociation and carbon chain growth, but also faces a challenge of controlling the rate of carbon deposition to avoid rapid deactivation. In this context, we synthesized a Mn-Al supported Fe catalysts exhibiting low carbon deposits by carefully controlling the metal-support interaction. Al may enhance the hydrothermal stability of FeCx, and facilitate the hydrogenation and desorption of hydrocarbons. These effects reduce the amount of carbon precursors on the surface so that the carbon coupling ability not only in carbon deposits but also in hydrocarbons can be weakened, and the Fe/Mn2Al1 exhibits the highest conversion (12.5 %) of CO and C2–4= yield (189. 9 g·kg−1cat·h−1).

Carbon Deposition Mechanisms on Ni-Based Anode for SOFC: A Comparison Between Non-Discharge and Discharge Modes

The nickel/yttria-stabilized zirconia (Ni/YSZ) and nickel/scandia-stabilized zirconia (Ni/ScSZ) have widely used as an anode for solid fuel cells (SOFCs). When hydrocarbon gas is supplied to the Ni-based fuel electrode of SOFCs, carbon is deposited on the anode, and it causes anode destruction. Therefore, carbon deposition control is required.The purpose of this study is to clarify carbon deposition mechanisms to understand how the carbon resistance appears on the Ni-based electrode in non-discharge and discharge modes. NiO/8XSZ powder with a binder was uniaxially pressed to form 0.7mm thick pellet (Ni : XSZ=50:50 vol%, X(dopant)=Y, Sc) which were subsequently sintered. After a reduction in H2 atmosphere, Ni/8XSZ sintered cells were heated in CH4/Ar (S/C ratio (Steam to Carbon) =0, CH4/Ar=0.25) and CH4/H2O/Ar atmosphere (S/C ratio=0.15, CH4/Ar=0.25) using a thermobalance, and the carbon deposition rates were measured from the weight change of the cell at 1173 K and 973 K. In this experiment, the S/C ratio was adjusted by bubbling CH4/Ar gas to set the saturated water vapor pressure at a given temperature. In addition, a power generation experiment of SOFC was conducted at 1073 K to investigate the effect of electrochemical reactions on the carbon deposition. The SOFC cells were prepared as follows. YSZ suspension was spin-coated on the NiO/8YSZ substrate. The electrolyte/electrode bilayer was co-sintered at 1673K. Then, a paste of LSM/YSZ was coated on electrolyte and sintered at 1473K. The cell was sealed to the alumina tube in the electric furnace. The anode side was fed with CH4/Ar/H2O (S/C ratio = 0.15) and the cathode side was exposed to O2. Current density was set to 126mA/cm2 for 30 min. After discharge, the anode surface was observed using SEM/EDS.As a result, the carbon deposition rate of Ni/ScSZ was lower than that of Ni/YSZ by 34 % at 1173 K and S/C=0 under non-discharge mode. This result indicated that the Ni/ScSZ exhibited superior carbon deposition tolerance than the Ni/YSZ at 1173 K. Steam reforming reaction was also different between the Ni/YSZ and Ni/ScSZ. Previous studies showed that carbon deposition tended to progress easily at the metal/solid electrolyte interface. The difference in carbon deposition behavior between Ni/YSZ and Ni/ScSZ was caused by the difference in the interface structure. On the other hand, the carbon deposition rate of Ni/ScSZ was higher than that of Ni/YSZ at 973 K which was opposite to that at 1173 K. Moreover, the rate of carbon reforming reaction (C+H2O→CO+H2) of Ni/YSZ was higher than that of Ni/ScSZ. In fact, the Ni/YSZ anode showed superior carbon tolerance than the Ni/ScSZ at lower temperature. XRD (X-ray Diffraction) analysis showed that the ScSZ with cubic structure was partially changed to the rhombohedral structure after the carbon deposition at high temperature while YSZ cubic structure was unchanged. This implied that the rhombohedral structure at the interface inhibited the carbon deposition reaction, suggesting that the electrolyte structure influenced the carbon deposition and steam reforming reactions. Therefore, it was shown that the electrolyte structure can control the carbon deposition while the same Ni was used. These findings give an useful hint to design the carbon tolerance electrode.Meanwhile, carbon deposition was not found on the Ni/YSZ surface after discharge at 1073 K. This indicated O2- ion improved the carbon tolerance during discharge. Comparison of carbon deposition between Ni/YSZ and Ni/ScSZ will be discussed using DFT (Density Functional Calculation).

Direct solar-driven thermochemical CO2-to-fuel conversion with efficiency over 39 % employing hierarchical triply periodic minimal surfaces biomimetic foam reactors

Solar-driven CO2 reforming of CH4 is considered a promising approach for achieving CO2 emission reduction and clean energy utilization simultaneously. However, reactors suffer from uneven temperature distribution and severe carbon deposition, leading to low solar-to-fuel efficiency. This study introduces a novel strategy for highly efficient solar-driven thermochemical CO2-to-fuel conversion based on hierarchical triply periodic minimal surfaces (TPMS) biomimetic foam reactors. The biomimetic hierarchical foam reactor exhibits a remarkably high light-to-fuel efficiency of 39.14 %, with CH4 and CO2 conversion rates reaching 72.6 % and 83.9 %, respectively, along with no obvious attenuation over 50 h. A 73.7 % reduction in temperature non-uniformity and a 96.9 % decrease in the carbon deposition rate are also demonstrated. The underlying mechanism is attributed to unique highly interconnected and smooth hierarchical pores, for which large pores promote the penetration of sunlight while small pores enhance fluid-solid energy transfer. Effects of solar irradiation conditions and foam thermal conductivity are investigated numerically, providing guides for further reactor optimization under different operating scenarios. This work presents a new approach for designing and manufacturing efficient direct solar-driven thermochemical CO2-to-fuel conversion reactors using hierarchical TPMS biomimetic foams.

Heterogeneous MgO-modified Ni3Sn cermet anode for hydrocarbon-fueled solid oxide fuel cells

To achieve the commercial application of solid oxide fuel cells (SOFCs), the performance degradation of the cell caused by carbon deposition needs to be well addressed. Here we report a new anode with nanostructured heterogeneous interfaces by integrating 0.38 wt% Sn and 0.19 wt% MgO into NiSDC for hydrocarbon-fueled SOFCs. The cell with 0.38Sn–0.19MgONiSDC anode exhibits a peak power density of 374 mW cm−2 and excellent long-term stability for 100 h with a power attenuation about 13.5% in humidified methane at 700 °C, which is attributed to the decreased rate of carbon deposition by promoting the formation of CO bonds instead of CC bonds, increasing the activation barrier for methane cracking and preventing the formation of nickel carbides by the confinement effect of heterogeneous catalysts, and the enhanced rate of carbon removal is attributed to excellent hydrophilicity and adsorption of CO2, as revealed by combined density function theory (DFT) calculations and experimental characterizations. This finding offers potential for the application of hydrocarbon-fueled SOFCs and provides a guide for designing coking-tolerant anodes.

Chemical looping gasification of benzene as a biomass tar model compound using hematite modified by Ni as an oxygen carrier

The effective removal of tar is a major challenge for biomass gasification. Schemes based on chemical looping gasification (CLG) offer a promising alternative for converting biomass into syngas with low tar content. The present work examined the influence of a Ni-modified oxygen carrier (OC) on the benzene conversion rate, hydrogen yield, carbon deposition rate, and yield of combustible gas products under various experimental conditions in the CLG of benzene as a model biomass tar compound. After modification, the NiFe2O4 OC exhibited good catalytic and oxidation performance. With the increase in reaction temperature and Ni loading, the hydrogen yield, benzene conversion rate, and carbon deposition rate all increased gradually. With the increase of weight hourly space velocity (WHSV), the benzene conversion rate decreased from 89.75% to 81.1%. which indicated that the oxidation capacity of the OC to benzene decreased. Meanwhile, the addition of steam significantly eliminated the carbon deposition, which decreased to 2.62% at an S/C ratio of 1.48. During the long-term experiment, the oxidation activity and catalytic activity of the OC each exhibit a slight decreased, which was possibly due to the sintering and agglomeration of the OC. Finally, the cracking mechanism of the tar model compound benzene was proposed.