The synthesis of ammonia is an energy-intensive process that consumes around 1.8% of global energy output each year and produces approximately 500 MMT of carbon dioxide. The production of hydrogen accounts for over 80% of the total energy required by the ammonia synthesis process. Haber-Bosch is the most widely used technology for ammonia production; however, it is only economically viable at a large scale. Oxidative steam reforming (OSR) is an alternative technology to produce synthesis gas for small-scale ammonia production. OSR combines the catalytic partial oxidation of methane (CPOM) and the steam reforming of methane (SMR) to efficiently generate a reformate with an H2/N2 molar ratio of 3, which is the stoichiometric value required for ammonia synthesis. One of the major challenges with OSR is the development of a catalytic material for CPOM that can show not only high activity and stability but also significant resilience to deactivation due to coke formation. In the present work, a novel and inexpensive nickel-based catalytic material has been synthesized using a facile sol-gel approach and tested for CPOM at temperatures below 500 degrees C. The prepared catalyst shows a remarkable activity comparable to that of catalysts based on noble metals and an outstanding resistance to the formation of carbon deposits. The catalytic activity is believed to result from the presence of carboxyl groups and oxygen-depleted regions, which led to an enhancement in the adsorption/activation of CH4 and O2, respectively. By using this catalytic material in the CPOM stage at 450 degrees C and an alumina-supported nickel catalyst in the SMR stage at 800 degrees C, we demonstrated the viability of an OSR reactor to produce a reformate with a suitable H2/N2 molar ratio for ammonia production.

Chemical separation membranes, drug delivery agents, and other nascent applications of metal-organic frameworks (MOFs) benefit from preparing MOFs as nanoparticles (nanoMOFs) and by controlling their particle surfaces. Despite the lack of deliberately added surface ligands, common examples of nanoMOFs exhibit multi-week colloidal stability in a range of polar solvents, in stark contrast with most conventional nanoparticles that require surface functionalization with bulky ligands. And yet, the origin of this stability remains unknown. Although nanoMOF zeta potentials exceed |±20 mV|, electrostatics alone cannot explain colloidal stability. Here, we demonstrate that nanoMOFs suspend only in solvents that dissolve the constituent MOF linkers. Moreover, the maximum “solubility” of nanoMOFs, i.e., the concentration of saturated particle suspensions, correlates with the solubility of the linkers in the same solvent. Calorimetry measurements indicate that nanoMOF immersion enthalpies resemble the solvation enthalpies of the linkers, suggesting solvent-linker interactions dictate nanoMOF colloidal stability. As a proof-of-concept, whereas nanoMOFs generally suspend only in polar solvents, we achieve toluene nanoMOF suspensions by identifying linkers soluble in toluene. Furthermore, atomistic molecular dynamics simulations reveal that solvents best at dissolving nanoMOFs are those that pack densely into the pores and interact with the MOF linkers. These results provide a predictive tool for achieving nanoMOF colloidal stability and highlight the uniqueness of defining a MOF “surface”, where solvents access both interior and exterior surfaces.

There is an increasing interest in using biogas as a renewable energy source to produce green hydrogen via steam reforming. The high-energy consumption associated with this process has motivated the pursuit of alternative approaches to process raw biogas at lower operating temperatures and without the need for large amounts of steam to prevent catalyst deactivation. The present study discusses the results obtained for the steam reforming of raw biogas in the presence of electric fields, using a nanocomposite catalytic material prepared by physically mixing yttria-stabilized zirconia and a Ni/Al2O3 catalyst. The experiments are conducted using a parallel plate capacitor reactor operated at 700 degrees C and 1 atm. The results indicate that by applying an external electric field (EEF) with a DC voltage of 1.9 kV and a current of 9 mA, a substantial increase in the rates of reaction can be attained. The conversions obtained for CH4 and CO2 are higher than the equilibrium values calculated in the absence of an EEF by 23% and 17%, respectively. This shift in the equilibrium is attributed to internal electric fields (IEFs) resulting from the interaction between YSZ and Ni/Al2O3, which leads to the creation of an interfacial nanopore structure that could increase the local IEF strength.

A metal-supported solid oxide fuel cell (MS-SOFC) consisting of infiltrated NiMo/CZ internal reforming catalysts is operated under a direct ethanol feed condition at 700 degrees C with a steam-to-carbon (S/C) ratio of 2. The additional catalyst functional layer is required to internally reform the ethanol fuel into syngas while preventing the cell's rapid deactivation due to unwanted carbon deposits or coking. Our experimental results show that the cell with NiMo/CZ catalyst shows a higher maximum current density of 0.355 A cm-2 compared to 0.052 A cm-2 for the cell without catalyst at 0.4 V. The constant current stability performance was also improved. The cell with NiMo/CZ can operate for 90 h and shows less carbon deposition than the cell without a catalyst. Adding NiMo/CZ reforming catalyst into the MS-SOFC is a promising solution to enhance the operating lifetime and coke resistance in the ethanol steam reforming fed MS-SOFC system.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Metal-Supported-SOFC (MS-SOFC) can handle rapid start-up and cool-down without cracking, making it more suitable for mobile applications than a conventional cermet-based SOFC, which is more susceptible to cracking when experiencing thermal shock due to its ceramic component. Despite having more robust mechanical properties, the MS-SOFC still relies on Ni as its anode catalyst, where it can be deactivated due to coking formation if the cell is operated under liquid logistics or hydrocarbon fuels. One of the most effective solutions is introducing a micro-reforming catalyst layer on the anode layer. The micro-reforming catalyst will reform the fuel into H2 and CO mixture called syngas, and then the anode will use the reformatted syngas to run the electrochemical reaction to produce electricity. This method will effectively improve the cell power output, stability, and coking resistance. In this work, we integrated the MS-SOFC with a reforming catalyst through the precursor infiltration method. We infiltrated a non-noble metal-based catalyst with a ceria-zirconia (CZ) into the MS-SOFC. The cell is then operated under direct ethanol fuel at 700 °C with the S/C ratio of 2. The non-noble metal catalyst is less expensive than noble but it also has lower catalytic activity and coking resistance during the cell operation in ethanol. Therefore, a regeneration cycle is necessary to maintain the cell performance and the catalytic activity of the cell. The regeneration cycle is performed by air pulsing directly into the cell’s anode surface to burn off the coking generated during the cell operation. The regeneration process involves a redox cycle that is only possible for a mechanically stable structure like MS-SOFC. Our experimental data showed that the MS-SOFC with infiltrated micro-reforming catalyst was gradually deactivated during the operation under ethanol fuel, indicated by the cell voltage drops due to coking. After the regeneration procedure with air pulsing, the cell voltage was recovered to its original performance. At the same time, the gas chromatograph detects a significant CO2 signal from the effluent gas, suggesting that the carbon removal process was successfully performed. Additionally, we observed an improvement in the cell’s performance under H2 and ethanol fuel. After a long-term constant current stability test, the cell shows up to ~20% and ~25% maximum current density drops under H2 and ethanol fuel, respectively, compared to its initial performance. Upon the cell regeneration with air pulse, the cell’s maximum current density was recovered to its initial performance and showed an improvement up to ~21 and 13% under H2 and ethanol, respectively, compared to its initial performance before the long-term test. This result suggests that some of the carbons might remain within the cell’s functional layer and help improve its conductivity and electrochemical performances. These data clearly show that the air pulsing regeneration process in the MS-SOFC can improve the cell’s lifetime by removing the coking deposit within the anode and enhancing its electrochemical and catalytic activity. ------- Figure Caption: Fig 1.(A) The IV pot of the MS-SOFC with reforming catalyst under H2 and (B) ethanol solution (S/C=2) at 700 °C of the MS-SOFC. The IV measurements were taken during its initial screening, after both constant current stability tests, and after both regeneration procedures. (C) Long-term stability test of the cell in ethanol solution under the constant current density of 125 mA/cm2. Figure 1

Electricity generation from solid oxide fuel cells (SOFCs) based power generator are in great demand for both stationary and automotive use. SOFC is considered as one of the best energy conversion devices that is available to demonstrate Nissan’s carbon neutrality goal by 2050. In particular, SOFCs are known for their fuel-flexible operations, for example, SOFCs can operate on renewable fuels such as ethanol, natural gas, jet-fuel, propane. Unlike H 2 based polymer fuel cell, the possibility of utilizing liquid fuels directly in SOFCs can pave the way to adopt the existing fuel infrastructure and can limit the greenhouse gas emissions significantly. This abstract presents the potential of using externally supported SOFCs, such as metal based SOFCs (metal-SOFCs) as the highly performing and durable power generator. It is identified that the metal-SOFC technology is a closest viable solution for using SOFCs in stationary and automotive applications.

A Metal-Supported-SOFC (MS-SOFC) has been modified by infiltrating a non-noble metal ceria-zirconia supported cobalt (Co/CZ) internal reforming catalyst to improve its reforming activity and inhibit the carbon deposition or coking under ethanol steam reforming conditions. Non-noble metal catalysts can still be deactivated during long-term cell operation in a severe coking-inducing environment. Therefore, an in-situ regeneration procedure was performed by pulsing air into the anode surface to burn the deposited carbon on the anode and catalyst layer during the cell operation. Upon the cell regeneration steps, the cell voltage was recovered to its initial condition at ~0.8 V, while the peak power density of the cell showed up to 116% recovery under H 2 and 111% recovery under ethanol. These data show that the air pulsing regeneration steps in the MS-SOFC can improve the lifetime by removing the coking deposit within the anode and further enhancing its electrochemical and catalytic activity.

Chemical separation membranes, drug delivery agents, and other applications of metal- organic frameworks (MOFs) benefit from preparing MOFs as nanoparticles (nanoMOFs) and by controlling the particle surface. Despite the lack of deliberately added surface ligands, common examples of nanoMOFs exhibit multi-week colloidal stability in a range of polar solvents, in stark contrast with most conventional nanoparticles requiring surface functionalization with bulky ligands, and yet the origin of this stability remains unknown. Here, we demonstrate that the “solubility” of nanoMOFs depends on the solubility of the constituent linkers and on the amount of exposed external surface area. Although the nanoMOF zeta potentials exceed |±20 mV|, these results indicate electrostatics alone cannot explain colloidal stability. Indeed, the identity of electrolyte ions at fixed ionic strengths induces divergent particle stabilities akin to the Hofmeister effect observed with proteins. Furthermore, nanoMOFs self-assemble into coronas with proteins to become stable under physiological conditions, even when similar surface charges between MOF and protein would be expected to repel. These results highlight the uniqueness of defining a MOF “surface” and suggest that nanoMOFs form a bridge between conventional nanoparticles and macromolecules, while opening fundamental questions into interfacial chemistry.

Caustic Aqueous Phase Electrochemical Reforming (CAPER) of ethanol produces pure compressed H2 at lower voltages, temperatures, and energy requirements than conventional electrolysis, while capturing carbonaceous products. The CAPER flow reactor consists of stainless steel endplates, stainless steel current collectors, and a Teflon flow field. The electrodes are prepared using commercial palladium nanoparticles on carbon support for the anode and platinum nanoparticles on carbon support for the cathode. The catalyst metal loading was 1 mg cm-2 on a 10 cm2 carbon cloth for both electrodes. Our CAPER reactor produces pure H2 at 80 bar and 80 degrees C applying voltages at <= 0.5 V. The only gas-phase product detected was H2 and any carbonaceous products were contained in the liquid phase. The H2 was produced with 97 +/- 4% faradaic efficiency. Operating at smaller electrode separation distances (4 mm) and 80 degrees C increased the current density. The highest lower heating value efficiency achieved was 28% at a flow rate of 0.05 mL min-1 and an applied voltage of 0.5 V. The compressed H2 was produced at <= 20 kWh kg-1, which is much lower than electrolysis systems that require upwards of 50 kWh kg-1.

Power generation from electrochemical devices based on solid oxide fuel cells (SOFCs) is in great demand for both stationary and automotive applications to achieve carbon neutrality goals by 2050. In particular, SOFCs are known for their fuel-flexible operations; for example, SOFCs can operate on simple and complex renewable fuels (such as ethanol, natural gas, jet fuel, propane, etc.). Unlike H 2 -based fuel cells, liquid and hydrocarbon fuels in SOFCs adopt the existing fuel infrastructure and contribute to reducing greenhouse gas emissions significantly. This article presents the potential of using metal-based SOFCs (metal cells) as highly performing and durable power generators. The metal cells technology could be the most accessible solution for using SOFCs for versatile industrial needs.

In this study, biorefinery residues and biomass ash were used to develop sulfonated carbon-based solid-acid catalysts to enhance xylan hydrolysis. Metals extracted from the biomass ash were impregnated into a carbon support prepared from biorefinery residues to synthesize sulfonated ash-impregnated carbon-based catalyst. Metals present in the ash most probably are responsible for the increased acid density in the catalyst. Using this catalyst, 11.4 % xylose yield was produced, an increase of 171 % over the yield obtained from a catalyst without ash impregnation. Using a xylan-to-catalyst ratio of 1:2, 72.9 % xylose yield was obtained, comparable to using 0.5 wt% sulfuric acid under the same reaction condition. Moreover, this catalyst significantly inhibited xylose dehydration, only forming 11.3 % furfural compared to that generated using dilute acid. Hence, these results show the potential for using biomass ash as a metal source to increase the number of acid sites in solid-acid catalysts used for biomass pretreatment.

Synthesized palladium-coated iron-iron oxide (Fe@FeOx/Pd) nanoparticles (NPs) using the successive salt reduction method are tested for their activity and stability toward formate oxidation (FO) and electrochemical CO2 reduction to formate (eCO(2)RF). The experimental results for FO show a current density at 0.12 V vs. Ag/ AgCl of 1.65 mA/cm(2) over 1 h, which is 16 times higher than that for Pd NPs. Furthermore, the same catalyst displays a higher current density with a faradaic efficiency (FE) of 95.6 % toward the eCO(2)RF, and exhibits a lower degree of CO adsorption. The iron-iron oxide interaction with the overlayer palladium is characterized by TEM/EDX, XPS/UPS, Mossbauer spectroscopy, and electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). NMR is used to estimate the amount of formate produced by the eCO(2)RF. A positive binding energy shift of the Pd 3d peak and the upshift of the d-band center as measured by XPS compared to monometallic homemade Pd NPs confirm that the electronic perturbation of the catalyst surface plays a major role in enhancing the performance of Fe@FeOx/Pd for both FO and eCO(2)RF. Furthermore, the work function as measured by UPS for the Fe@FeOx/Pd material is lower than that for monometallic Pd confirming a change in chemical properties of the catalyst surface. Finally, Mossbauer spectroscopy is used to determine the composition, structure and nature of all sites of the Fe@FeOx substrate before use and the perturbation of their intrinsic properties by the Pd overlayer. This change in intrinsic properties of the Pd coated material provides additional explanations for the electrochemical improvement measured for this catalyst toward both FO and eCO(2)RF.

Global warming and climate change enhanced by the high atmospheric CO 2 concentration have been correlated to the frequency of extreme weather causing a significant amount of property damage and loss of human lives. Among current atmospheric CO 2 concentration control strategies, the electrochemical reduction of CO 2 (eCO 2 R) process is a promising technology that can utilize CO 2 gas as a feedstock to produce valuable C 1 and C 2 compounds at room temperature. Since the eCO 2 R reaction is limited by high activation energy and mass transfer, the choice of the electrocatalyst and the configuration of the CO 2 electrolyzer have a significant impact on the activity and selectivity of the eCO 2 R process. This review discusses current technological advancements of electrocatalytic materials and the design of the gas diffusion electrodes that increase energy efficiency and reduce the mass transfer resistance of the CO 2 conversion into C 1 with a focus on formate and C 2 chemical compounds. A techno-economic analysis is briefly provided, and future and technical challenges of the CO 2 conversion at the industrial scale into formate and C 2 products are also addressed.

Lithium–oxygen batteries based on four-electron conversion to LiOH have demonstrated great potential for next-generation high-energy batteries. However, the understanding of LiOH-based cathode chemistry remains incomplete. Here, we use systematic characterization techniques to study LiOH chemistry, revealing that “high-performance” LiOH chemistry is achieved at the expense of electrolyte degradation and is irreversible in commonly used liquid organic electrolytes. LiOH forms via four-electron reduction of O2 during discharge, whereas LiOH decomposes via one-electron oxidation during charge. This one-electron oxidation of LiOH generates surface-reactive hydroxyl species that aggressively degrade organic electrolytes. The reaction mechanisms are further supported by computational studies. Our findings suggest that the key to enable reversible LiOH chemistry is bypassing surface-reactive hydroxyl formation or using stable solid-state electrolytes, which can be explored by future research. Our findings also shed lights on the reversibility of four-electron cathode chemistries in other metal–air batteries.

We report the synthesis and characterization, reaction kinetics, and deactivation mechanism of a series of catalysts with metallic nickel (Ni) and molybdenum carbide (Mo2C) particles supported on zeolite Y (Ni-Mo2C/FAU) in methane steam reforming (MSR) reaction at 850 degrees C. Despite a low Ni loading of 2.4 wt%, MSR on Ni-Mo2C/FAU exhibits high activity and stability, yet deactivation of Ni-FAU is significant. Further investigations elucidate that the catalyst deactivation is caused by Ni particle sintering via Ostwald ripening instead of coking, and steam induces hydroxylated Ni surface that accelerates sintering. Moreover, Mo2C boosts the activity and stability of Ni on zeolite Y by enhancing CH4 activation rather than activating H2O. The interplays among Mo2C and Ni particles dynamically balance the carbon formation and consumption rates, and inhibit Ni sintering. This study demonstrates that high MSR activity and stability can be achieved on transition metal carbide - Ni catalysts with systematically tuned compositional, structural, and interfacial factors.

In this work, we introduce a Rhodium-Ceria-Zirconia (Rh/CZ) internal reforming catalyst layer to a highperformance metal-supported solid oxide fuel cell (MS-SOFC). The catalyst is applied by infiltrating Rh, CeO2, and ZrO2 precursors into the stainless steel (SS 430) support. The cell is tested by directly feeding an ethanol solution (45 vol%) into the anode at 600 ?. Our experimental results show that the button cell with the infiltrated 5 wt% Rh/CZ demonstrates an improved performance over the button cell without the catalyst layer by enhancing the internal reforming activity of ethanol toward the production of synthesis gas. The maximum current density improved from 0.3 A cm-2 to 0.4 A cm(-2) while the long-term stability was also greatly improved. Post mortem cell analysis reveals that the infiltrated catalyst layer can prevent severe coke deposition from the cell's anode functional layer. The proposed integrated reforming catalyst and MS-SOFC system is a promising pathway to enable bioethanol fed-SOFC technology for future electric vehicles.

Global warming and climate change enhanced by the high atmospheric CO2 concentration have been correlated to the frequency of extreme weather causing a significant amount of property damage and loss of human lives. Among current atmospheric CO2 concentration control strategies, the electrochemical reduction of CO2 (eCO2R) process is a promising technology that can utilize CO2 gas as a feedstock to produce valuable C1 and C2 compounds at room temperature. Since the eCO2R reaction is limited by high activation energy and mass transfer, the choice of the electrocatalyst and the configuration of the CO2 electrolyzer have a significant impact on the activity and selectivity of the eCO2R process. This review discusses current technological advancements of electrocatalytic materials and the design of the gas diffusion electrodes that increase energy efficiency and reduce the mass transfer resistance of the CO2 conversion into C1 with a focus on formate and C2 chemical compounds. A techno-economic analysis is briefly provided, and future and technical challenges of the CO2 conversion at the industrial scale into formate and C2 products are also addressed.

The LiOH-based cathode chemistry has demonstrated potential for high-energy Li-O-2 batteries. However, the understanding of such complex chemistry remains incomplete. Herein, we use the combined experimental methods with ab initio calculations to study LiOH chemistry. We provide a unified reaction mechanism for LiOH formation during discharge via net 4 e(-) oxygen reduction, in which Li2O2 acts as intermediate in low water-content electrolyte but LiHO2 as intermediate in high water-content electrolyte. Besides, LiOH decomposes via 1 e(-) oxidation during charge, generating surface-reactive hydroxyl species that degrade organic electrolytes and generate protons. These protons lead to early removal of LiOH, followed by a new high-potential charge plateau (1 e(-) water oxidation). At following cycles, these accumulated protons lead to a new high-potential discharge plateau, corresponding to water formation. Our findings shed light on understanding of 4 e(-) cathode chemistries in metal-air batteries.

This paper investigates the effects of molybdenum promoter and silica oxide (SiO2) support morphology on the ethanol steam reforming (ESR) performance of Nickel-Molybdenum (NiMo) bimetallic catalysts. Ordered mesoporous SiO2 (SBA-15) and commercial SiO2 supports were used as the oxide support materials. The synthesized catalysts were prepared via the wet impregnation method and characterized via XRD, H2-TPR, BET, FTIR, and Raman techniques. This study shows that NiMo bimetallic catalyst supported on SBA-15 has superior catalytic activity and better coking resistance at an intermediate temperature of 600 degrees C than commercial SiO2 supported catalysts. The presence of a uniform mesoporous structure of SBA-15 with an average pore diameter of - 2 nm can obstruct the carbon formation, leading to improved coking resistance. The catalytic enhancement of NiMo bimetallic catalysts toward ESR can also be linked to the ability of Mo promoter in enhancing the interaction between NiMo nanoparticles and SiO2 support materials and restraining agglomeration of Ni nanoparticles, which results in further improvement of NiMo nanoparticle dispersion and inhibit its sintering. The NiMo bimetallic catalysts supported on SBA-15 illustrated the high H2 yield of - 54% and carbon conversion of - 89% with the excellent stability for ESR performed at 600 degrees C and the steam-to-carbon ratio of 2 over 65 h.

최근 바이오가스의 이용은 폐기물 및 온실가스 배출을 줄이는 동시에 지속적인 에너지 수요 증가에 대응할 수 있는 방안으로 여겨지고 있으며, 따라서 전 세계적으로 바이오가스 사용량은 점차 증가하고 있다. 또한, 바이오가스는 재생에너지로서 전기, 열의 생산뿐만 아니라 기존 화석 연료를 대체 가능한 바이오메탄, 메탄올, 합성액체연료, 수소 등의 화학 물질을 생산할 수 있는 자원으로 평가되고 있다. 본 논문에서는 바이오가스를 이용한 수송용 연료 생산 기술 개발 동향과 그린 수소 생산 기술의 최근 연구 동향을 소개하였으며, 신기술로서 전기장부과 촉매 반응을 이용한 CO₂ 포함 바이오가스로부터 그린 수소 생산 기술에 대해 반응물 CH₄과 CO₂ 전환율 향상과 촉매 탄소 침적 안정성 등의 주요 연구 결과를 나타내었다.