Catalysts For Decomposition Research Articles

Discovery of Alloy Catalysts for Ammonia Decomposition by Machine Learning-Based Prediction of Adsorption Energies

Ammonia decomposition has gained significant attention as an eco-friendly method for hydrogen production because it creates no carbon dioxide emissions. While Ru catalysts are known for their high activity in ammonia decomposition, their high cost makes them uneconomical for commercial use. Therefore, it is essential to explore novel alloy catalysts composed of inexpensive elements with high catalytic performance. Nitrogen adsorption energies serve as key descriptors indicating the catalytic performance for ammonia decomposition, and first-principle calculations can compute these energies. However, the screening of numerous alloy catalyst candidates through extensive first-principle calculations and experimental validations remains time-consuming due to the vast number of potential candidates. To address this, artificial intelligence and machine learning models are being developed to quickly predict catalyst performance, efficiently searching for promising catalyst candidates. In this study, we developed a machine-learning-based method to rapidly predict nitrogen adsorption energies using a graph-based artificial neural network, thereby efficiently searching for novel catalysts for ammonia decomposition. Our training dataset included the nitrogen adsorption energies of 30 pure transition metal catalyst candidates, as well as binary alloy catalyst candidates, including core-shell and intermetallic compounds. As a result, we successfully identified 12 catalyst candidates composed of inexpensive elements that are likely to exhibit catalytic performance comparable to Ru catalysts.

Single-atom Barium Promoter Enormously Enhanced Non-noble Metal Catalyst for Ammonia Decomposition.

As a well-established topic, single-atom catalyst has drawn growing interest for its high utilization of metal. However, researchers prefer to develop various active metals with single-atom form, the intrinsic roles of single-atom promoters are usually underrated, which are significant in boosting reaction activity. In this work, Ba single atoms were in situ prepared in the Co-Ba/Y2O3 catalyst with crystallized BaCO3 as the precursor under the ammonia decomposition reaction condition. The optimized Co-Ba/Y2O3 catalyst achieves extremely high H2 production rate of 138.3 mmolH2·gcat-1·min-1 at very low temperature (500 °C, GHSV = 840,000 mL·g-1·h-1) and Co-Ba/Y2O3 exhibits excellent durability during the 350 h test, which realizes the highest activity among all non-noble catalysts, and reaches or even exceeds numerous reported Ru-based catalysts. Both Y2O3 and Co demonstrate positive interactions with Ba, which significantly facilitates the dispersion of Ba species at high temperatures (≥ 600 °C). Ba single atoms significantly enhance the charge density of Co and form additionally active Co-O-Ba-Y2O3 interfacial sites, which alleviates hydrogen poisoning and decreases the reaction barrier of the N-H bond activation of *NH. The exploration of atomically dispersed promoters is groundbreaking in heterogeneous catalysis, which opens up a whole new domain of catalytic material.

Разложение аммиака на Co-Al2O3 /SiO2 катализаторах: влияние способов восстановления кобальта

The focus on "green" energy requires the search for environmentally friendly energy storage systems. The reason for choosing ammonia as a potential storage for hydrogen is its high energy capacity and the absence of carbon and nitrogen oxide emissions during decomposition. Herein, we tested Co-Al2O3/SiO2 ammonia decomposition catalysts that had been pre-activated via cyclic hydrogenation-carburization-hydrogenation (RCR) and reduction-oxidation-reduction (ROR) procedures versus the conventional cobalt oxides reduction with hydrogen (R). The samples were characterized by H2-TPR, TEM and synchrotron X-ray diffraction techniques, which revealed that the structural properties of the catalysts were not modified by the reaction. Since the activities of the tested catalysts and the effective reaction barriers appeared to be close, the easiest-to-prepare catalyst R was chosen for the long-term catalytic trial (500 h), and it showed excellent performance stability.

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Synergetic Effect of Ni‐CeO₂ Bimetallic Catalyst for an Effective Decomposition of Methane to Hydrogen and Filamentous Nanocarbons

AbstractThe work attempts to synthesis nickel‐ceria bimetallic catalysts supported on porous carbon template, thermally stable at 850 °C, for dehydrogenation of methane to hydrogen and carbon nanostructures. A series of bimetallic Ni catalysts were synthesized by varying the % ceria content (30Ni‐5CeO2/AC, 30Ni‐10CeO2/AC, and 30Ni‐15CeO2/AC) using the incipient wetness impregnation approach. Among the set of bimetallic catalysts, the 30Ni‐5CeO2/AC catalyst was found to offer highest methane conversion and stability. A maximum conversion of 90 % was achieved with 40 % methane feed concentration along with good catalyst stability. The promoter ceria at low concentration enhanced the dispersion of metal over the catalytic surface, resulting in adequate metal‐support interaction. The ability of the carbon support along with promoter ceria enhanced the thermal stability of the Ni catalyst up to 850 °C, offering high conversion and catalyst stability has been the highlight of the work. Advanced analytical techniques were used to characterize the catalyst's structural, textural, and morphological properties both before and after the reaction. The morphological study of the best‐performing catalyst demonstrated the formation of dense carbon nanotubes through tip‐growth mechanism exhibiting a high aspect ratio.

Effects of nitrogen vacancy sites of oxynitride support on the catalytic activity for ammonia decomposition

Nitrogen-containing compounds such as imides and amides have been reported as efficient materials that promote ammonia decomposition over nonnoble metal catalysts. However, these compounds decompose in an air atmosphere and become inactive, which leads to difficulty in handling. Here, we focused on perovskite oxynitrides as air-stable and efficient supports for ammonia decomposition catalysts. Ni-loaded oxynitrides exhibited 2.5–18 times greater catalytic activity than did the corresponding oxide-supported Ni catalysts, even without noticeable differences in the Ni particle size and surface area of the supports. The catalytic performance of the Ni-loaded oxynitrides is well correlated with the nitrogen desorption temperature during N2 temperature-programmed desorption, which suggests that the lattice nitrogen in the oxynitride support rather than the Ni surface is the active site for ammonia decomposition. Furthermore, NH3 temperature-programmed surface reactions and density functional theory (DFT) calculations revealed that NH3 molecules are preferentially adsorbed on the nitrogen vacancy sites on the support surface rather than on the Ni surface. Thus, the ammonia decomposition reaction is facilitated by a vacancy-mediated reaction mechanism.

The bimetallic 3,5-dinitrobenzoate composites: A flexible-synergistic catalysts for high-performance decomposition of ammonium perchlorate

Composites of metal complexes have catalytic effects on the thermal decomposition of ammonium perchlorate (AP), while the kinetics and mechanism studies of the processes are seldom mentioned. Here, composite microspheres of cupric 3,5-dinitrobenzoate and cobalt 3,5-dinitrobenzoate [(3,5-DNB)Cox•Cuy] were synthesized and employed to research the kinetics and mechanism of AP catalytic decomposition. The decomposition peak temperature of AP in the presence of the (3,5-DNB)Cox•Cuy microspheres decreased from 403 °C (pure AP) to 288 °C, and the released heat increased by 384.5–745.6 J/g. Notably, the (3,5-DNB)Cox•Cuy microspheres significantly improved the kinetic rate constant by 1.83–37.75 times. The (3,5-DNB)Cox•Cuy microspheres exhibited higher activity than their corresponding single components for the thermal decomposition of AP, indicating excellent synergistic effects and proposing a possible mechanism. Understanding the kinetics and mechanism of the catalytic process developed in this study could further improve the decomposition performance of AP.

Microstructure of highly effective platinum–iridium alloys as catalysts for hydrogen peroxide decomposition

Microstructure of highly effective platinum–iridium alloys as catalysts for hydrogen peroxide decomposition

Cation induced electrostatic adsorption driven self-assembly sandwich-like α-MnO2/MXene for efficient self-heating photothermal synergistic catalytic decomposition of carcinogenic gaseous formaldehyde

Realizing self-assembly between different nanoparticles is an important strategy for constructing novel nanostructures or excellent functional composites. Formaldehyde is the primary gaseous pollutant in indoor air, and achieving its ambient temperature decomposition is of great significance for improving indoor air quality. This research reports an electrostatic adsorption driven self-assembly strategy, constructing a sandwich structure α-MnO2/MXene for self-heating photothermal synergistic catalytic decomposition of formaldehyde. The self-assembly process and electrostatic adsorption driven mechanism were detailed. A comparative study was conducted on the performance and mechanisms of the self-assembled sandwich structure and mechanically mixed α-MnO2/MXene in the self-heating photothermal catalytic decomposition of formaldehyde. The sandwich structure α-MnO2/MXene with built-in electric field and Schottky barrier exhibited excellent self-heating photothermal catalytic activity for formaldehyde decomposition, realizing the 100% mineralization of formaldehyde under simulated solar-light irradiation at room temperature; even with the irradiation of visible light, the sandwich structure α-MnO2/MXene can still maintain 82.6% HCHO conversion. Furthermore, we elucidated the self-heating photothermal catalytic mechanism, shedding light on the distinct roles and contributions of photocatalysis and thermal catalysis. It was found that the photothermal catalytic mechanism of the sandwich structure α-MnO2/MXene-S composite involved a thermally assisted photocatalytic process. The advantages of the self-assembled sandwich structure and its mechanism for enhancing photothermal performance were fully revealed. This study reports an effective strategy for electrostatic adsorption self-assembly, offering a fresh perspective on developing non-noble metal catalysts for ambient-temperature formaldehyde decomposition

Innovative Design of anode materials for Li-ion batteries: Bismuth oxide/sodium bismuth molybdate nanocomposites

Novel bismuth oxide/sodium bismuth molybdate nanocomposites (NCs), Bi2O3@NaBi(MoO4)2, were developed successfully via simple methods. Advanced analyses revealed that the NCs were composed of Bi2O3 and NaBi(MoO4)2 particles at the nanoscale, below 10 nm, in a combination of amorphous and crystalline forms. In this work, these NCs were utilized as lithium-ion battery anode materials for the first time, demonstrating exceptional electrochemical performances, including high capacity, superior capacity retention, high coulombic efficiency, excellent rate capacity, and pseudo-capacitance behavior. For instance, Bi2O3@NaBi(MoO4)2 NCs prepared at 1 h and 3 h of reaction time delivered a reversible charge capacity of 1052 and 1034 mAh g−1 after 200 cycles at current densities of 0.1 A g−1 with a capacity retention of 110 and 129 %, respectively. Notably, all the NCs anodes exhibited an excellent initial coulombic efficiency of above 80 %. Materials characterizations and electrochemical analysis revealed that the improved electrochemical properties of the NCs were attributed to their unique architectures, which featured nanostructures, molybdate components, and a small amount of amorphous phase. In addition, the significant capacity increase could be due to the electrochemical milling effect, the in situ formation of metallic particles, and the role of Mo metal in the NCs anodes as the catalysts for Li2O decomposition during cycling. It concluded that Bi2O3@NaBi(MoO4)2 NCs have great potential as advanced anodes for Li-ion storages.

{Co4O4} Cubanes in a conducting polymer matrix as bio-inspired molecular oxygen evolution catalysts

Exploration of efficient molecular water oxidation catalysts for long-term application remains a key challenge for the conversion of renewable energy sources into fuels. Cuboidal {Co4O4} complexes keep attracting interest as molecular water oxidation catalysts as they combine features of both heterogeneous and homogeneous catalysis with bio-inspired motifs. However, the application of many cluster-based catalysts for the oxygen evolution reaction still requires new stabilization strategies. Drawing inspiration from the stabilizing effects of natural polymers, we introduce a conductive polymer-hybrid approach to covalently immobilize {Co4O4} cubane oxo clusters as oxygen evolution catalysts. Polypyrrole is applied as an efficient p-type conducting polymer that promotes hole transfer during the oxygen evolution reaction, resulting in higher turnover frequency compared to the pristine {Co4O4} oxo cluster and heterogeneous Co-oxide benchmarks. The asymmetric coordination of {Co4O4} not only mitigates catalyst decomposition pathways, but also increases the catalytic efficiency by exposing a directed cofacial dihydroxide motif during catalysis.

Metal-doped nanocages (Fe-Si76, Fe-C76, and Fe-Al38N38) as potential catalysts for ozone decomposition to oxygen molecules

Metal-doped nanocages (Fe-Si76, Fe-C76, and Fe-Al38N38) as potential catalysts for ozone decomposition to oxygen molecules

NiCoCr2O4 as a potential catalyst for the thermal decomposition of ammonium nitrate: a kinetic investigation

The thermal decomposition of high energetic materials plays an important role in their thermal performance. Use of the catalyst is one of the efficient ways improve the thermal performance of the high energetic materials. Therefore, in this work nickel cobalt chromite (NiCoCr2O4) prepared using precipitation approach was utilized as a catalyst for decreasing the thermal decomposition temperature and activation energy of high energetic material ammonium nitrate (AN). The results suggest that AN/NiCoCr2O4 decomposes at lower temperature (240 °C) within a short temperature range (Thermo gravimetry decomposition curve = 180–250 °C). The kinetic study was investigated using Kissinger-Akahira-Sunose (KAS) and Kissinger method (5, 10, and 15 °C min−1 heating rates). The activation energy of AN was reduced from 158.0 to 141.5 kJ mol−1 and decrease in the pre-exponential factor was observed upon addition of NiCoCr2O4. The outcome of the present work can be used to design AN based high energetic formulations containing NiCoCr2O4 catalyst with better thermal decomposition performance.

Mechanism for airborne ozone decomposition on X-MIL-53(Fe) (X = H, NH2, NO2)

Ground−level ozone (O3) pollution poses a significant threat to both ecosystem sustainability and human health. The catalytic decomposition of O3 presents as a promising technology to address the issues of O3 pollution. This study undertook the synthesis of various functionalized metal−organic framework (MOF) catalysts (i.e., X-MIL-53(Fe) (X = H, NH2, NO3)) to delve into the influence of ligand functional groups on skeletal structure and catalytic efficacy, particularly focusing on unraveling the mechanism of O3 catalytic decomposition under humid conditions. NH2-MIL-53(Fe) catalyst achieved complete O3 decomposition under ambient temperature and high humidity conditions (RH=75 %), exhibiting a reaction rates (mol·m−2·s−1) 129 and 10.5 times greater than that of MIL-53(Fe) and NO2-MIL-53(Fe). The NH2 group promotes electron flow within the backbone towards the hydroxyl group (OH) linked to Fe atom. In humid O3, H2O molecules augment the interaction between O3 and NH2-MIL-53(Fe), and OH is converted to·O2− after deprotonation, promoting O3 decomposition. Additionally, leveraging three−dimensional (3D) printing technology, a monolithic catalyst for O3 decomposition was prepared for application. This study not only advances understanding of the mechanisms underlying O3 decomposition but also offers practical solutions for addressing O3 pollution at humid conditions.

Designing sulfide catalysts for H2S dissociation to H2 based on reaction descriptors and microkinetics

Molybdenum disulfide (MoS2) is a promising catalyst for the challenging transformation of hydrogen sulfide (H2S) into sulfur and hydrogen (H2). However, a detailed understanding of its structure-function correlation still needs to be provided. We used density functional theory calculations to extract relevant reaction indexes (binding energies and free energy barriers) over different MoS2 surfaces. We used these indexes as inspiration in developing new catalysts and a microkinetic model to compare the results, extracting insights into the reaction mechanisms and surface coverages. The turnover frequencies obtained experimentally and through microkinetic modeling are analogous, validating our approach. The findings pave the way for developing more efficient H2S decomposition catalysts and establish a descriptor-based design for other metal sulfide catalysts.

Enhancing CO2 conversion in a temperature-controlled DBD plasma reactor with HKUST-1 catalyst: Water removal and CuO/Cu2O-derived approach

Due to a synergy effect, using dielectric barrier discharge (DBD) plasma technology combined with catalysts for CO2 decomposition, a major contributor to global warming, is recognized as an effective approach to transforming CO2 into valuable products such as CO, which is a crucial feedstock for chemical synthesis. Herein, HKUST-1 was synthesized using the hydrothermal method for CO2 conversion in the DBD reactor. To enhance catalyst performance in the plasma region, HKUST-1 was treated with O2 plasma to increase its specific surface area. Additionally, HKUST-1 was calcined at 300 °C to produce the CuO/Cu2O catalyst. Since the recombination reaction in the CO2 conversion is increased at higher temperatures, the reactor heat is removed using fan cooling and a water circulation system. In the presence of the HKUST-1 catalyst, the CO2 conversion rate significantly increased by 132 %, 82 %, and 12 % in reactors operating without cooling, with fan cooling, and with water cooling circulation, respectively compared to the reactors without catalyst, at a flow rate of 50 ml/min and maximum input power. The catalysts have been characterized using a comprehensive suite of analytical techniques, including FTIR, XRD,TEM, SEM, EDS, and BET analysis. The BET analysis indicates that the specific surface area of HKUST-1 after O2 plasma treatment is increased by 52 %, which causes an increasing conversion rate of up to 18 %. The CuO/Cu2O catalyst demonstrated maximum CO2 conversion of 21 % at an input power of 140 W and achieved energy efficiency of 8.6 % at 40 W. The presence of oxygen vacancies within this catalyst enhances the process of CO2 decomposition.

Highly efficient Co-added Ni/CeO2 catalyst for co-production of hydrogen and carbon nanotubes by methane decomposition

The catalytic decomposition of methane (CDM) is a hydrogen and nanostructured carbon production process with minimal CO2 emission. Among the transition metal-based catalysts (e.g. Ni, Fe, Co, etc.), Ni-based catalysts are most widely studied due to the higher catalytic activity in decomposing methane. However, the limited lifespan of the catalyst makes it unsuitable for practical applications. Effective methane decomposition catalysts should be designed to optimize both reaction efficiency and catalyst lifetime. A Ni/CeO2 catalyst, developed in previous studies, Co was added to promote low-temperature (< 700 °C) activity manipulating the redox property of Co. Among the prepared catalysts with varying Ni:Co ratio, the methane conversion rate of the Ni8Co2/CeO2 catalyst was approximately twice that of the Ni10/CeO2 catalyst, confirming its excellent low-temperature activity. The reaction rate of Ni8Co2/CeO2 catalyst was 4.38 mmol/min∙gcat at 600 °C with WHSV of 36 L/gcat∙h. In terms of characteristics of carbon products, Raman spectroscopy analysis revealed that the carbon grown on the catalyst surface exhibited high crystallinity, with D-G band ratio (ID/IG) of 1.01. The fresh and used catalyst samples were characterized by TEM, XPS, XAS, and other methods to analyze the parameters affecting catalytic activity.

Highly effective direct conversion of H2S into COx-free H2 and S at low temperature over novel MoxC@ZrO2 microwave catalysts

Direct decomposition of H2S into H2 and S is an attractive alternative to the Claus process, because COx-free H2 and S can be simultaneously recovered from an abundant and toxic waste gas, which has huge social economic and ecological environmental benefits. However, it is still a great challenge to achieve the direct H2S decomposition reaction with high efficiency due to the thermal equilibrium limitation. Herein, a core-shell structured MoxC@ZrO2 was developed as novel microwave catalyst for microwave catalytic H2S decomposition. More specifically, the H2S conversion over MoxC@ZrO2 catalyst is as high as 99.9% at 650 °C, which immensely surpasses the H2S equilibrium conversion (6.1% at 650 °C). This study provides an effective strategy for the design of highly active microwave catalysts, and supplies a strategy for efficiently catalytic decomposition of H2S waste and recovering high-value hydrogen and sulfur at lower reaction temperatures.

Hemilabile and Redox-Active Quinone Ligands Unlock sp3-Rich Couplings in Nickel-Catalyzed Olefin Carbosulfenylation.

A three-component coupling approach toward structurally complex dialkylsulfides is described via the nickel-catalyzed 1,2-carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N-S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N-S electrophile containing an N-methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol%. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox-active ligands that tune the steric and electron properties of the metal throughout the catalytic cycle. DFT calculations show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni-catalyzed 1,2-carbosulfenylation-binding as an η6 capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X-type redox-active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, while binding as an η1 L-type ligand to promote N-S oxidative addition at a relatively more electron-rich and sterically less crowded Ni(I) center.

Hemilabile and Redox‐Active Quinone Ligands Unlock sp3‐Rich Couplings in Nickel‐Catalyzed Olefin Carbosulfenylation

A three‐component coupling approach toward structurally complex dialkylsulfides is described via the nickel‐catalyzed 1,2‐carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N–S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N–S electrophile containing an N‐methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol%. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox‐active ligands that tune the steric and electron properties of the metal throughout the catalytic cycle. DFT calculations show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni‐catalyzed 1,2‐carbosulfenylation—binding as an η6 capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X‐type redox‐active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, while binding as an η1 L‐type ligand to promote N–S oxidative addition at a relatively more electron‐rich and sterically less crowded Ni(I) center.