Cost Of Catalyst Research Articles

Optimizing Fe-N-C Electrocatalysts for PEMFCs: Influence of Constituents and Pyrolysis on Properties and Performance

Proton exchange membrane fuel cells (PEMFCs) are promising alternative technologies with applications in stationary power systems, vehicles, and portable electronics due to their low temperature operation, fast start-up, and environmental advantages. However, the high cost of platinum-based catalysts, in particular for the oxygen reduction reaction (ORR) of the cathode side, prevents their widespread incorporation. Fe-N-C electrocatalysts have emerged as viable alternatives to platinum. In this study, different precursor components were investigated for the way that they affect the pyrolysis process, which is crucial for tailoring the final catalyst properties. In particular, carbon allotropes such as carbon Vulcan, Ketjenblack, and carbon nanotubes were selected for their unique structures and properties. In addition, various sources of iron (FeCl2, FeCl3, and K[Fe(SCN)4]) were evaluated. The influence of the pyrolysis atmosphere on the resulting Fe-N-C catalyst structures was also assessed. Through an integrated structure and surface chemistry analyses, as well as electrochemical tests with rotating disk electrode experiments in acidic media, the ORR performance and stability of these catalysts were defined. By examining the relationships between carbon sources and iron precursors, this research provides valuable information for the optimization of Fe-N-C catalysts in fuel cell applications.

Carbon-coated ZnS as a high-performance ORR/OER bifunctional cathode catalyst for zinc-air batteries

The commercial application of zinc-air batteries (ZABs) is hindered by the high cost and scarcity of precious metal catalysts. In this paper, we prepared high-performance ORR/OER bifunctional catalysts with a carbon-coated ZnS spherical structure (ZnS@C) through a hydrothermal method followed by a carbonization process. Characterized by their unique spherical coated pore structure, exhibit impressive electrocatalytic activity. Specifically, ZnS@C-2, produced by a secondary carbonization process demonstrates an ORR half-wave potential of 0.82 V (relative to RHE) and an OER overpotential of 377 mV at 10 mA cm−2. When employed in a ZAB, it achieves a maximum power density of 120.4 mW cm−2, a specific capacity of 836 mAh gZn−1, and maintains cycle stabilization for up to 165 h at 10 mA cm−2. The research results demonstrate that the unique carbon-coated internal porous structure not only significantly enhances the stability of the catalyst but also increases the number of active sites, thereby providing more abundant activation energy for the catalytic reaction and facilitating its efficient progress. This underscores the catalyst's excellent ORR and OER properties, suggesting promising practical application potential.

Methanol-assisted NO oxidation under an oxygen atmosphere for efficient denitration: Experiments and ReaxFF-MD simulations

The development of selective catalytic reduction technologies for controlling nitrogen oxide (NOx) emissions in flue gas is hampered by high equipment and catalyst costs. In this study, a catalyst-free and efficient denitration process using methanol and oxygen as reactants was developed. Various gas atmospheres with differing concentrations were investigated to remove NO without catalysts. The addition of methanol significantly enhanced NO removal efficiency, reaching 94.6 % at 550 °C, with 55.1 % of NO converted to NO2, which can be absorbed by downstream alkali solutions. Reactive force field molecular dynamics (ReaxFF-MD) simulations were employed to analyze the atomic level NO oxidation mechanism in the CH3OH/NO/O2/H2O homogeneous reaction system. The simulation revealed the generation pathway of three key oxidizing intermediates (OH, HO2, and H2O2) and their roles in NO oxidation. This study offers critical insights into developing a cost-effective denitration process, highlighting the potential for improved NOx emission control.

Iron (II) catalyzed cyclization of ketoxime acetates with triethyl orthoformate: An easy access to symmetrical pyridines

A simple and efficient iron (II) catalyzed approach to the synthesis of symmetrical pyridines has been demonstrated using ketoxime acetates and triethyl orthoformate in DMF at 120 °C under nitrogen environment. In this strategy, significantly, triethyl orthoformate functions as C1 carbon source and which is noteworthy. Other benefits of this process include good yields, high functional group tolerance, low cost of catalyst and avoiding of use of hazardous chemicals.

Unveiling the heterojunction of Fe3O4@MXene nanocatalyst for ultrafast degradation of antibiotics via non-radical pathway

The transfer of advanced oxidation processes (AOPs) to real-world applications faces several technology challenges involving oxidation performance, catalyst cost, poor reactive oxygen species (ROS) yield, and long-term stability. This work aims to develop a reactive, efficient, and stable MXene-based nanocatalyst, namely Fe3O4@Ti3C2Tx, for ultrafast removal of the selected sulfonamide antibiotics. As revealed by extensive nanocatalyst characterization, the MXene surface not only anchors Fe/Fe3O4 nanoparticles (NPs) but also prevents NP agglomeration. Notably, the conductive interface between MXene and Fe3O4 promotes the Fe(II)/Fe(III) redox cycle and accelerates peroxymonosulfate (PMS) activation. The Fe3O4@Ti3C2Tx demonstrates excellent catalytic activity by achieving complete sulfamethoxazole (SMX) degradation within 6 min and maintained its catalytic activity after 5 continuous cycles. In the Fe3O4@Ti3C2Tx/PMS system, multiple ROS (e.g., •OH, SO4•-, O2•-) are involved but 1O2 was found to be the primary ROS for SMX degradation. The presence of co-exiting inorganic impurities and pH changes may hinder SMX degradation. Finally, elucidating possible degradation pathways of SMX would greatly aid in treating antibiotic-containing wastewater.

Synthesis and Design Strategies of MXene Used as Catalysts

AbstractMXene have found extensive applications in various fields, including catalysis. Two predominant roles of MXene in catalysis are as catalyst carriers or as catalysts themselves. The former has received significant attention and is addressed in other publications. This review assesses MXene and its derivatives as direct catalysts, which is particularly intriguing due to its potential to reduce the design cost of catalysts. Moreover, an in‐depth discussion of this aspect aids in understanding the true role of MXene in catalysis, beyond its role as a catalyst carrier. For instance, MXene and its derivatives have been extensively employed as photocatalysts, with their catalytic activity significantly influenced by their structural characteristics. Furthermore, due to MXene's remarkable light absorption capacity, it is crucial to explore the contributions of photothermal generation or photocatalytic‐thermocatalytic synergistic effects. Additionally, MXene has demonstrated remarkable electrocatalytic performance in hydrogen production. Moreover, MXene exhibits promising applications in thermal catalysis, such as dehydrogenation and oxidation. A deeper understanding of these aspects can help researchers further design MXene‐based nanomaterials, or alleviate their oxidation. Finally, we offer insights into the future research directions of MXene from our perspective. This review could provide guidance for the design of novel MXene catalysts for industrial applications.

Effect of catalyst and oxidant concentrations in a TEMPO oxidation system on the production of cellulose nanofibers.

In traditional TEMPO oxidation systems, the high cost of TEMPO catalysts has been a significant barrier to the industrialization of oxidized CNF. From an economic perspective, presenting the characteristics of various CNFs produced with the oxidation systems with reduced catalyst usage could facilitate the industrial application of CNF across a wide range of fields. In this study, it was demonstrated that reducing the amount of TEMPO catalyst used (from 0.1 to 0.05 mmol g-1) in a conventional oxidation system increased the carboxylate content by approximately 6.3%. Furthermore, the activation of hydroxyl amine TEMPO, which is generated after the oxidation reaction of cellulose, was enhanced by adjusting the dosage of the inexpensive oxidant NaClO, leading to a 20% improvement in carboxylate content. This suggests that controlling the amount of NaClO as an oxidant can be a key parameter in adjusting the dosage of TEMPO to achieve the targeted degree of surface substitution. Results from the dispersion stability, UV-transmittance, and morphological properties of TEMPO-oxidized CNF using microfluidizing treatment showed that high carboxylate content plays a crucial role in producing high-purity CNF suspensions, which are small, uniform, and free from microfibers. Additionally, by varying the number of mechanical treatments applied to the oxidized cellulose, various types of CNF suspensions with different mean widths were obtained. We expect that these findings offer meaningful insights to end-users seeking a breakthrough in the performance limitations of final applications using cellulose nanomaterials.

Regulating the location relationship between Cu nanoparticles and Pt atoms to enhance the catalytic hydroisomerization performance: Together or apart?

Single atom catalysts have been recently reported as the efficient catalysts for hydroisomerization compared to the conventional nanoparticle catalyst. Despite the fascinating advantage in enhancing the metal activity or reducing the catalyst cost, the long-term stability of the single atom catalyst seemed not that satisfactory, especially when reacting under atmospheric pressure. Herein, Pt single atom catalysts were combined with Cu nanoparticles by different means to explore a new way to improve the catalytic performance. Cu nanoparticles were located away from Pt sites to form a binary catalyst, or acted as the support of Pt atoms to form a single atom alloy (SAA) catalyst. With the binary catalyst Pt1–0.1Cu@CS, the conversion of the n-heptane after time on stream of 50 h increased to 70.3 %, higher than Pt1@CS (47.3 %). Besides, excessive Cu nanoparticles in the binary catalyst were found rather harmful to the catalysis instead. However, the SAA catalyst Pt1Cu@SAPO-11 showed a poor activity in hydroisomerization compared to Pt1@CS, indicating that the alloy structure should go against the activation of reactant. The roles of Pt atoms and Cu nanoparticles in different catalysts were discussed in detail. The reaction mechanism of hydroisomerization was refined with the different functions of the dual metal sites. This work might be instructive for the design of single atom catalysts combined with metal nanoparticles.

Repurposing waste-iron electrocoagulated algal biomass as effective heterogenous (bio)electro-fenton catalyst for phthalate removal from wastewater

The presence of refractory micropollutants in natural waters poses significant environmental and health risks. Preferably, advanced oxidation techniques like electro-Fenton (EF) and bio-electro-Fenton (BEF) are used to mitigate micropollutants; nevertheless, their field-scale implementation is limited by prohibitive catalyst cost. As an alternative, waste-iron electrocoagulated algal biomass (A-BC/Fe) was explored as a heterogeneous Fenton catalyst to eliminate dimethyl phthalate (DMP) from wastewater. The Fenton-conducive morphological, chemical, and electrochemical properties of the A-BC/Fe catalyst were revealed by detailed characterisation. In EF treatment, 10 mg/L of DMP was completely degraded within 15 min at pH of 7.0, 50 mM Na2SO4, and cathode potential of − 1.4 V vs. Ag/AgCl. Moreover, the EF system achieved 87.80 ± 2.10% and 96.14 ± 1.10% of DMP removal from secondary and tertiary treated municipal sewage, respectively. The A-BC/Fe catalyst-driven EF process disintegrated DMP into benign non-toxic by-products and showed stable performance over eight batch cycles with only a 1.71% decline in DMP removal efficiency. Further, the A-BC/Fe-catalysed BEF system eliminated 94.81 ± 1.90% of DMP in 4 h while achieving a maximum power density of 124.03 ± 5.64 mW/m2. This investigation underscores the potential of repurposing electrocoagulated algal biomass as a sustainable heterogenous catalyst for micropollutant remediation.

Ultralow Ru-doped NiFe catalyst on stainless-steel fibers for enhanced oxygen evolution reaction in anion-exchange membrane water electrolysis

Designing high-performance, stable electrodes for the oxygen evolution reaction (OER) is essential for anion-exchange membrane water electrolysis (AEMWE) in industrial-scale hydrogen production. AEMWE has not yet been commercialized due to the high cost of precious metal catalysts and unsatisfactory performance of non-precious metal catalysts. Although various anodes are being developed to replace expensive Ir-based catalysts, low-cost catalysts that demonstrate a balance of performance and stability remain limited. In the present study, we fabricated a NiFe catalyst on a corrosion-resistant stainless-steel fiber paper substrate using a simple electrodeposition method and introduced small amounts of Ru via galvanic displacement. In half-cell tests, an enhanced overpotential of 229 mV was observed for the Ru-NiFe/SS anode at 10 mA/cm2. Using Ru-NiFe/SS as an anode for OER in AEMWE assembled with a commercial Pt/C cathode exhibited high performance with a current density of 8.73 A cm−2 (at 2.05 Vcell and 80℃). Long-term stability tests also showed that the Ru-NiFe/SS anode had higher stability than commercial IrO2 electrodes at 1 A cm−2 and 80℃ for 50 h. Therefore, Ru-NiFe/SS can be considered an alternative to conventional Ir-based electrodes to reduce hydrogen production costs.

Porous biochar-driven innovative Cr(VI) reduction and resource recovery

Catalyst-mediated Cr(VI) reduction face significant challenges in by-product ion residues and catalyst cost. The development of low-cost catalysts and catalytic technologies with near-zero impurity introduction is therefore of great practical importance. This study developed a pristine biochar-mediated nanoconfinement strategy that facilitated the chemical reaction between oxalic acid (OA) and Cr(VI) with a stoichiometric ratio of 3.3:1. The method achieved the simultaneous Cr(VI) reduction and OA removal, and completed the chromium removal process with near-zero impurity introduction after a precipitation process. While traditional catalyst-mediated reduction relied on mechanisms of functional group or active sites, this study took a novel path by adopting a focus on pore size. The structure–activity relationship, and experimental design demonstrated the predominant role of porous properties in the reaction, thus proposing a nanoconfinement Cr(VI) reduction mechanism. Continuous flow results revealed a treatment capacity of 1750 mL/h for the complete removal of Cr(VI) from Cr electroplating rinse water. The effluent, precipitated with CaO, had 0.06 mg/L of total Cr and 0.56 mg/L of OA, while the precipitate, recovered as CaCr2O4, demonstrated a total Cr recovery efficiency of 90.4%. Compared to industrial Cr(VI) chemical reduction, this study minimizes impurity introduction to the catalytic system. This study explores an effective strategy for Cr(VI) reduction and Cr resource recovery using low-cost pristine biochar, and provides navigation for the removal and resource utilization of other heavy metals or radionuclides.

Tuning the crystallinity of Cu-based electrocatalysts: Synthesis, structure, and activity towards the CO2 reduction reaction

The rising levels of CO2 have spurred growing concerns for our environment, and curbing CO2 emissions may not be practically viable with the expanding human population. One attractive strategy is the electrochemical CO2 reduction (CO2RR) into value added chemicals but because of the chemical inertness of the CO2 molecule, the electrochemical reduction requires a suitable catalyst. Cu-based catalysts have been largely investigated for CO2RR, however, the difficulty achieving a high selectivity and faradaic efficiency towards specific products, especially hydrocarbons, is still a challenge, alongside the concern over cost, stability and scarcity of the metal catalyst. The present research focuses on tuning the crystallinity of Cu nanoparticles via a green, cost-friendly, and facile method, called the urea glass route. Remarkably, the incorporation of a selected nitrogen-carbon rich source (namely, 4,5 dicyanoimidazole) at low temperatures allow the formation of an oxidized derived amorphous Cu system, whilst a second thermal treatment enables the transformation to crystalline Cu0. We found that the combination of surface Cu0 and Cu1+ (observed via XPS studies) present in our amorphous and crystalline Cu nanoparticles leads to interesting differences in the final catalytic activity when tested under CO2 reaction conditions. The combination of extended X-ray absorption fine structure (EXAFS) experiments and molecular dynamics simulations provides compelling evidence for the amorphous and metallic nature of Cu nanoparticles.

Conversion of waste paper sludge into magnetic biochar for activation of peroxydisulfate for tetracycline removal

ABSTRACT The Fe2+-peroxydisulfate (PDS) process is an effective method to enhance paper sludge dewaterability. However, the generated waste of iron-rich sludge cake needs to be disposed of properly. Converting sludge cake into magnetic biochar catalysts can help to shorten its environmental risks, recover resources, and reduce catalyst costs. In this work, the magnetic sludge biochar (Fe-SBC) was prepared and applied as a PDS activator to remove tetracycline (TC). Results showed that the Fe-SBC pyrolyzed at 600 °C presented excellent catalytic activity for PDS to degrade TC (rate of 74.89%) under the optimum conditions (intrinsic pH, 10 mM PDS, 0.5 g/L Fe-SBC, and 50 mg/L TC). It was found for the first time that the addition sequences of the biochar catalyst and PDS were insignificant on TC removal. Furthermore, the TC removal mechanism was proposed to be free radicals (·OH, SO4·−, and O2−·) and non-radical (1O2) pathways working together for TC removal, for which 1O2 was dominated. In addition, coexisting ions (Cl− and CO32−) had an inhibitory effect on TC degradation. This work will provide a new recycling approach for waste paper sludge in wastewater treatment.

Less is more: Optimisation of variable catalyst loading in CO[formula omitted] electroreduction

The electrochemical conversion of CO2 is a promising method of carbon-neutral chemical production. However, commercial realisation in aqueous electrolytes is challenging, due to competition with the hydrogen evolution reaction (HER), and the propensity for CO2 to participate in the carbonate equilibrium reactions. These two phenomena are linked through OH− ions, as both the by-product of the catalytic reactions and the culprit behind the parasitic carbonate reactions. By reducing the local catalyst loading where the CO2 concentration is low, the HER is decreased more than the reactions that are dependent on CO2 as a reactant. Therefore, it is possible to improve reaction selectivity and reactant utilisation while reducing the capital cost of catalyst. We demonstrate this theory through an analytical solution of a 1D flow electrolyser model. We extend this to a comprehensive model of a contemporary gas-diffusion electrode (GDE) setup. We find that the operation costs are dominated by the electrolyser power consumption and, to a lesser degree, the cost of CO2 and its recovery at the anode. We numerically obtain the catalyst loading profiles that maximise operating profit. The optimisation process reveals that profits are maximised for high gas flow rates, and consequently, low single pass conversions, where the CO2 concentration is as high as possible. However, when lower gas flow rates are used for practical reasons, variable catalyst loadings are shown to lead to significant operational improvements, especially in the production of higher C products that require a greater number of electrons transferred. The model is made freely available in MATLAB and its use is encouraged in determining the applicability of variable catalyst loading to future experimental setups.

Porous nickel-based catalyst doped with fluorine can efficiently electrocatalyze the reduction of CO2 to CO

The electrocatalytic carbon dioxide reduction reaction (CO2RR) to produce high-value-added products is considered an effective method for achieving carbon neutrality and mitigating greenhouse effects. However, due to the coexistence of competing hydrogen evolution reaction (HER) alongside CO2RR, the selectivity of catalysts still requires improvement. Moreover, the complex preparation methods and high cost of noble metal catalysts pose challenges. Therefore, it is crucial to find a catalyst that is easy to prepare, cost-effective in terms of raw materials, and exhibits high selectivity. In this study, chitosan was utilized as a carbon source for the catalyst, with nickel as the primary metal. Through gasification at 650°C and morphology control via formation of hollow structures using Cd metal particles, along with F doping modification, an electrocatalyst (NiCd650F0.2) was prepared. This catalyst exhibited the highest CO selectivity of 90.3 % at −1 V vs. RHE, with a CO partial current density of −10.68 mA·cm−2 at −1.2 V vs. RHE. Stability tests demonstrated that its selectivity and activity remained excellent over 8 hours. Density functional theory (DFT) calculations further indicated that F doping significantly lowers the adsorption energy barrier of reactions, promoting reaction kinetics and enhancing catalyst selectivity.

Techno-economic analysis of the direct solar conversion of carbon dioxide into renewable fuels

Direct conversion of carbon dioxide (CO2) using sunlight into commercially viable renewable fuels will be one key solution for decarbonization and storing renewable solar energy. However, the direct conversion of CO2 using sunlight faces uphill challenges, especially the techno-economic viability (TEV), as the produced fuels must compete with fossil fuels or at least with fossil fuel alternatives, which are cheap. This work proposes an innovative structure design for photoelectrochemical reduction of CO2 into renewable fuels and performs a detailed techno-economic analysis (TEA) using a generalized gross margin (GM) model. The proposed structure uses low-cost and earth-abundant crystalline silicon-based photoanode with triangle nano-strips on a thin-film substrate to efficiently convert solar energy into renewable fuels. The proposed structure shows 20.01% of power-conversion efficiency (ηPEC). The techno-economic GM model considers all relevant cost parameters to assess the TEV of the produced hydrogen (H2) and hydrocarbon (C1–C3) fuels from CO2 reduction processes. The TEV of the produced renewable fuels is analyzed and presented against critical device parameters, such as the photocurrent density (J), catalyst’s durability (tdur), Faradaic efficiency (FE), and catalyst cost (Ccat). We also analyzed how sensitively the TEV of the produced fuels depends on the uncertainty of different cost parameters assuming base-, worst-, and optimistic-case scenarios. We find that carbon monoxide (CO) and formic acid (HCOOH) fuels will be commercially viable in the base case, while H2 and propanol (C3H7OH) will be only in the optimistic case.

Green Hydrogen Production by Low-Temperature Membrane-Engineered Water Electrolyzers, and Regenerative Fuel Cells.

Green hydrogen (H2) is an essential component of global plans to reduce carbon emissions from hard-to-abate industries and heavy transport. However, challenges remain in the highly efficient H2 production from water electrolysis powered by renewable energies. The sluggish oxygen evolution restrains the H2 production from water splitting. Rational electrocatalyst designs for highly efficient H2 production and oxygen evolution are pivotal for water electrolysis. With the development of high-performance electrolyzers, the scale-up of H2 production to an industrial-level related activity can be achieved. This review summarizes recent advances in water electrolysis such as the proton exchange membrane water electrolyzer (PEMWE) and anion exchange membrane water electrolyzer (AEMWE). The critical challenges for PEMWE and AEMWE are the high cost of noble-metal catalysts and their durability, respectively. This review highlights the anode and cathode designs for improving the catalytic performance of electrocatalysts, the electrolyte and membrane engineering for membrane electrode assembly (MEA) optimizations, and stack systems for the most promising electrolyzers in water electrolysis. Besides, the advantages of integrating water electrolyzers, fuel cells (FC), and regenerative fuel cells (RFC) into the hydrogen ecosystem are introduced. Finally, the perspective of electrolyzer designs with superior performance is presented.

Ensuring Stability of Anode Catalysts in PEMWE: From Material Design to Practical Application.

Proton Exchange Membrane Water Electrolysis (PEMWE) has emerged as a clean and effective approach for the conversion and storage of renewable electricity, particularly due to its compatibility with fluctuating photovoltaic and wind power. However, the high cost and limited performance of iridium oxide catalysts (i.e. IrO2) used as anode catalyst in industrial PEM electrolyzers remain significant obstacles to widespread application. Although numerous low-cost and efficient alternative catalysts have been developed in laboratory research, comprehensive stability studies critical for industrial use are often overlooked. This leads to the failure of performance transfer from catalysts tested in liquid half-cell systems to those employed in PEM electrolyzers. This concept presents a thorough overview for the stability issues of anode catalysts in PEMWE, and discuss their degradation mechanisms in both liquid half-cell systems and PEM electrolyzers. We summarize comprehensive protocol for the assessment and characterization, analyze the effective strategies for stability optimization, and explore the opportunities for designing viable anode catalysts for PEM electrolyzers.

Regulating the Interaction Between PdCu Bimetals and MgAl1.82Ce0.18O4 Spinel for Three‐Way Catalysis

AbstractThree‐way catalysis represents a pivotal technology for converting automobile exhaust pollutants into non‐toxic gases. Substituting some noble metals with transition metals is considered a promising way to reduce catalyst costs. Herein, we have investigated the catalytic potential of different configurations of Pd−Cu catalysts prepared by impregnation (PdCu/MA), sol‐gel (PdCu‐MA), impregnation with physical mixing (Pd/Cu/MA) and sol‐gel with physical mixing (Pd/Cu‐MA) to modify the interaction of Pd/Cu and MgAl1.82Ce0.18O4 (MA) spinel in this comparative study. The different structures in these catalysts lead to different catalytic performances. PdCu/MA exhibits the best three‐way catalytic performance, which owe to the small‐sized PdCu particles with high Pd2+ content (45.3 %) and optimal interaction of Pd/Cu particles and MgAl1.82Ce0.18O4 support. Furthermore, comprehensive CO‐DRIFTS, H2‐TPR, and O2‐TPD analyses discover that the metal‐support interaction is beneficial to enhance the catalytic performance in three‐way catalysis. Overall, we demonstrated that the interaction between PdCu bimetals and support can regulate the electronic state of Pd, thereby enhancing the use and efficiency of noble metals.

Economic limitation of recent heterogeneous catalysts for ammonia synthesis

The economic performance of newly developed catalysts for ammonia synthesis, Ru/Ca(NH2)2 and Ru/Pr2O3, are evaluated by process simulation using Aspen Plus©. The results show that the high activity of the new catalysts reduces the electricity cost for pressurizing reactant gases; however, the electricity for lowering the temperature in ammonia separation through liquefaction is significant due to the mitigated pressure and almost compensates for the decreased cost. The results show an economic limitation to current research trends that develop a catalyst for ammonia synthesis under low pressure. It is noted that catalyst costs are high due to expensive ruthenium; thus, the lifetime of catalysts significantly influences the total cost. With the assumption of a long lifetime of catalysts, the new catalysts are advantageous when the electricity cost is high, the characteristics of the case in which renewable energy is employed. As the future direction of the catalyst development, recycling or extending the lifetime of the catalysts and replacing Ru with cheap metal will be crucial from the economic viewpoint. Moreover, effective methods for ammonia collection, such as adsorbents, should be focused on reducing the electricity of ammonia liquefaction in cooling separation and giving a vital meaning to the condition mitigated by the newly developed catalysts.