Inert Molecules Research Articles

Selective Monoborylation of Methane by a Mono Bipyridyl‐Nickel(II) Hydride Catalyst

We report the development of an earth‐abundant metal catalyst for methane C‒H borylation. The post‐synthetic metalation of bipyridine‐functionalized zirconium metal−organic framework (MOF) with NiBr2, followed by treatment of NaEt3BH affords MOF‐supported monomeric bipyridyl‐nickel(II) dihydride species via active site isolation. The heterogeneous and recyclable nickel catalyst selectively borylates methane at 200 ºC using pinacolborane (HBpin) to afford CH3Bpin in 61% yield with a turnover number (TON) up to 1388. The confinement of the active NiH2‐species within the uniformly porous MOF allows selective monoborylation of methane via shape‐selective catalysis by preventing the formation of sterically encumbered overborylated products. Unlike MOF‐Ni catalyst, its homogeneous control is almost inactive in methane borylation due to its intermolecular decomposition. Our mechanistic investigation, including spectroscopic, kinetic, and control experiments, as well as DFT calculations, revealed that stabilizing mononuclear bipyridyl‐nickel dihydride and diboryl species by MOF is crucial for achieving efficient methane borylation via turnover‐limiting σ‐bond metathesis. This work shows promise in designing MOF‐based abundant metal catalysts for the chemoselective functionalization of methane and other inert molecules into valuable chemicals.

Selective Monoborylation of Methane by a Mono Bipyridyl-Nickel(II)Hydride Catalyst.

We report the development of an earth-abundant metal catalyst for methane C‒H borylation. The post-synthetic metalation of bipyridine-functionalized zirconium metal-organic framework (MOF) with NiBr2, followed by treatment of NaEt3BH affords MOF-supported monomeric bipyridyl-nickel(II) dihydride species via active site isolation. The heterogeneous and recyclable nickel catalyst selectively borylates methane at 200 ºC using pinacolborane (HBpin) to afford CH3Bpin in 61% yield with a turnover number (TON) up to 1388. The confinement of the active NiH2-species within the uniformly porous MOF allows selective monoborylation of methane via shape-selective catalysis by preventing the formation of sterically encumbered overborylated products. Unlike MOF-Ni catalyst, its homogeneous control is almost inactive in methane borylation due to its intermolecular decomposition. Our mechanistic investigation, including spectroscopic, kinetic, and control experiments, as well as DFT calculations, revealed that stabilizing mononuclear bipyridyl-nickel dihydride and diboryl species by MOF is crucial for achieving efficient methane borylation via turnover-limiting σ-bond metathesis. This work shows promise in designing MOF-based abundant metal catalysts for the chemoselective functionalization of methane and other inert molecules into valuable chemicals.

Modelling the Tuning of the Cooperativity in Spin Crossover Sandwiched Layers

AbstractThis work is devoted to the investigation of the influence of the embedding surfaces (substrates) on a spin crossover layer in the framework of a mechanoelastic model. We analyze how the properties of the spin crossover molecules (i. e. the thermal transition or the cluster spreading) situated inside a 2D layer are influenced by interactions between them and the inert molecules situated on two parallel surfaces, embedding the spin crossover layer. We conclude that the thermal transition is influenced both at the macroscopic scale (the shape and wdith of the hysteresis accompanying the thermal transition) and at the microscopic scale (formation of clusters) by the presence of epitaxial interactions with substrates. Equally, we analyse how the spin transition modulates the pressure exerted by the middle layer on the two substrates. The last part of the paper is devoted to the study of the possibility to induce the switching of molecules in the inner layer by heating the embedding surfaces.

Radiation-Synthesized Metal-Organic Frameworks with Ligand-Induced Lewis Pairs for Selective CO2 Electroreduction.

The electrochemical activation of inert CO2 molecules through C─C coupling reactions under ambient conditions remains a significant challenge but holds great promise for sustainable development and the reduction of CO2 emission. Lewis pairs can capture and react with CO2, offering a novel strategy for the electrosynthesis of high-value-added C2 products. Herein, an electron-beam irradiation strategy is presented for rapidly synthesizing a metal-organic framework (MOF) with well-defined Lewis pairs (i.e., Cu- Npyridinic). The synthesized MOFs exhibit a total C2 product faradic efficiency of 70.0% at -0.88V versus RHE. In situ attenuated total reflection Fourier transform infrared and Raman spectra reveal that the electron-deficient Lewis acidic Cu sites and electron-rich Lewis basic pyridinic N sites in the ligand facilitate the targeted chemisorption, activation, and conversion of CO2 molecules. DFT calculations further elucidate the electronic interactions of key intermediates in the CO2 reduction reaction. The work not only advances Lewis pair-site MOFs as a new platform for CO2 electrochemical conversion, but also provides pioneering insights into the underlying mechanisms of electron-beam irradiated synthesis of advanced nanomaterials.

Preferred Electric Field Mechanism for Frustrated Lewis Pair Reactivity.

This study employs computational methods to investigate the mechanism of H2 activation by frustrated Lewis pair (FLP) species, including both intermolecular and intramolecular nitrothane/borane FLP systems. Previous studies have proposed two qualitative reactivity mechanism models to explain the facile cleavage of H2 by FLPs. The findings of this study support the electric field mechanism as the favorable pathway for H2 cleavage. Utilizing frontier molecular orbital theory and energy decomposition analysis, the study explores the electronic structure and nature of the reactions under an external electric field (EEF). Analysis using the activation strain model highlights the significant influence of geometrical deformation energies of FLPs on the activation barriers of H2 activation reactions. Computational results suggest that H2 activation by FLP molecules follows the electric field mechanism, indicating the potential of the FLP/EEF combination as an effective activator for inert molecules.

Spin Manipulation of Co sites in Co9S8/Nb2CTx Mott-Schottky Heterojunction for Boosting the Electrocatalytic Nitrogen Reduction Reaction.

Regulating the adsorption of an intermediate on an electrocatalyst by manipulating the electron spin state of the transition metal is of great significance for promoting the activation of inert nitrogen molecules (N2) during the electrocatalytic nitrogen reduction reaction (eNRR). However, achieving this remains challenging. Herein, a novel 2D/2D Mott-Schottky heterojunction, Co9S8/Nb2CTx-P, is developed as an eNRR catalyst. This is achieved through the in situ growth of cobalt sulfide (Co9S8) nanosheets over a Nb2CTx MXene using a solution plasma modification method. Transformation of the Co spin state from low (t2g 6eg 1) to high (t2g 5eg 2) is achieved by adjusting the interface electronic structure and sulfur vacancy of Co9S8/Nb2CTx-P. The adsorption ability of N2 is optimized through high spin Co(II) with more unpaired electrons, significantly accelerating the *N2→*NNH kinetic process. The Co9S8/Nb2CTx-P exhibits a high NH3 yield of 62.62µg h-1 mgcat. -1 and a Faradaic efficiency (FE) of 30.33% at -0.40V versus the reversible hydrogen electrode (RHE) in 0.1m HCl. Additionally, it achieves an NH3 yield of 41.47µg h-1 mgcat. -1 and FE of 23.19% at -0.60V versus RHE in 0.1m Na2SO4. This work demonstrates a promising strategy for constructing heterojunction electrocatalysts for efficient eNRR.

Sulfur defect engineering boosted nitrogen activation over FeS2 for efficient electrosynthesis of ammonia

Electrocatalytic nitrogen (N2) reduction to ammonia (NH3) reaction (eNRR) supplies a promising alternative to the Haber-Bosch technology. However, the dissociation of NN bond hinders its development. Herein, sulfur vacancies are introduced into FeS2 for promoting N2 activation and thus stimulating the eNRR progress. Experimental investigations and density functional theory (DFT) calculations reveal that the electrons could transfer from Fe 3d orbits to N2 2π* orbital, thus facilitating the cracking of inert N2 molecules. And the electron transfer is easier for those Fe atoms with S vacancies in adjacent positions. Furthermore, we find that eNRR process on the FeS2 surface follows the distal and alternating hybrid pathway. Also, the water molecules in the electrolyte facilitate the first hydrogenation of N2 (*N2 → *NNH). Notably, FeS2 with rich sulfur vacancies exhibits an excellent NH3 yield rate of 67.5 μg h−1 mgcat.−1, which outperforms most of the reported eNRR activities of Fe-based catalysts.

Ethanol synthesis via catalytic CO2 hydrogenation over multi-elemental KFeCuZn/ZrO2 catalyst.

Technological enablers that use CO2 as a feedstock to create value-added chemicals, including ethanol, have gained widespread appeal. They offer a potential solution to climate change and promote the development of a circular economy. However, the conversion of CO2 to ethanol poses significant challenges, not only because CO2 is a thermodynamically stable and chemically inert molecule but also because of the complexity of the reaction routes and uncontrollability of C-C coupling. In this study, we developed an efficient catalyst, K-Fe-Cu-Zn/ZrO2 (KFeCuZn/ZrO2), which enhances the EtOH space time yield (STYEtOH) to 5.4 mmol gcat -1 h-1, under optimized conditions (360 °C, 4 MPa, and 12 L gcat -1 h-1). Furthermore, we investigated the roles of each constituent element using in situ/operando spectroscopy such as X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). These results demonstrate that all components are necessary for efficient ethanol synthesis.

Nanomaterial-Mediated Immunosensors and Their Performance in Detecting Tumor Markers.

The detection of tumor markers is crucial for assessing the progression of specific cancers. Numerous research studies have shown that immunosensors can convert immune-specific response biosignals into visual signals, enabling the highly sensitive tracking and detection of tumor markers. This offers a promising solution for early cancer diagnosis. However, most tumor markers are inert molecules that are challenging to detect at low concentrations in the early stages of cancer. Therefore, there is a need to develop immunosensor analysis platforms with a higher sensitivity. Nanomaterials, with their advantages of high stability, low cost, and versatility in design, have emerged as ideal candidates for enhancing the performance of immunosensor analysis. In this paper, we review the design ideas of nanomaterials in antibody-based electrochemical, electrochemiluminescent, and photoelectrochemical immunosensors, including electrode interface modification, signaling probes for stimulating sensing signals, and design strategies of modified materials in signaling mechanisms. In addition, we have thoroughly analyzed the performance, advantages and disadvantages of different immunosensors. Therefore, the aim of this paper is to review the recent advances in advanced nanomaterial strategies for different immunosensors and their biomedical applications, and to point out the challenges and prospects of immunosensors in future clinical applications.

Highly Efficient Nitrogen Reduction to Ammonia through the Cooperation of Plasma and Porous Metal-Organic Framework Reactors with Confined Water.

While the ambient N2 reduction to ammonia (NH3) using H2O as hydrogen source (2N2+6H2O=4NH3+3O2) is known as a promising alternative to the Haber-Bosch process, the high bond energy of N≡N bond leads to the extremely low NH3 yield. Herein, we report a highly efficient catalytic system for ammonia synthesis using the low-temperature dielectric barrier discharge plasma to activate inert N2 molecules into the excited nitrogen species, which can efficiently react with the confined and concentrated H2O molecules in porous metal-organic framework (MOF) reactors with V3+, Cr3+, Mn3+, Fe3+, Co2+, Ni2+ and Cu2+ ions. Specially, the Fe-based catalyst MIL-100(Fe) causes a superhigh NH3 yield of 22.4 mmol g-1 h-1. The investigation of catalytic performance and systematic characterizations of MIL-100(Fe) during the plasma-driven catalytic reaction unveils that the in situ generated defective Fe-O clusters are the highly active sites and NH3 molecules indeed form inside the MIL-100(Fe) reactor. The theoretical calculation reveals that the porous MOF catalysts have different adsorption capacity for nitrogen species on different catalytic metal sites, where the optimal MIL-100(Fe) has the lowest energy barrier for the rate-limiting *NNH formation step, significantly enhancing efficiency of nitrogen fixation.

Highly Efficient Nitrogen Reduction to Ammonia through the Cooperation of Plasma and Porous Metal‐Organic Framework Reactors with Confined Water

While the ambient N2 reduction to ammonia (NH3) using H2O as hydrogen source (2N2+6H2O=4NH3+3O2) is known as a promising alternative to the Haber‐Bosch process, the high bond energy of N≡N bond leads to the extremely low NH3 yield. Herein, we report a highly efficient catalytic system for ammonia synthesis using the low‐temperature dielectric barrier discharge plasma to activate inert N2 molecules into the activated nitrogen species, which can efficiently react with the confined and concentrated H2O molecules in porous metal‐organic framework (MOF) reactors with V3+, Cr3+, Mn3+, Fe3+, Co2+, Ni2+ and Cu2+ ions. Specially, the Fe‐based catalyst MIL‐100(Fe) causes a superhigh NH3 yield of 22.4 mmol g‐1 h‐1. The investigation of catalytic performance and systematic characterizations of MIL‐100(Fe) during the plasma‐driven catalytic reaction unveils that the in situ generated defective Fe‐O clusters are the highly active sites and NH3 molecules indeed form inside the MIL‐100(Fe) reactor. The theoretical calculation reveals that the porous MOF catalysts have different adsorption capacity for nitrogen species on different catalytic metal sites, where the optimal MIL‐100(Fe) has the lowest energy barrier for the rate‐limiting *NNH formation step, significantly enhancing efficiency of nitrogen fixation.

Controllable Construction of a Mo2C/MoO2 Interface with an Ideal Mo2C/MoO2 Ratio for Efficient Electrocatalytic Nitrogen Reduction to Ammonia.

Electrocatalytic nitrogen reduction reaction (NRR) is considered to be a viable contender for the production of NH3. However, due to the sluggish adsorption and activation of the electrocatalyst toward inert N2 molecules, there is an urgent need for developing effective catalysts to facilitate the reaction. Inspired by natural nitrogenase, in which Mo atoms are the active centers, Mo-based electrocatalysts have received considerable attention, but further exploration is still necessary. Interface-engineered electrocatalysts can effectively optimize the absorption and activation of the catalytic active center for N2 and thus improve the electrocatalytic activity of NRR. However, the lack of studies for controllably constructing an optimal ratio of two phases at the interface hinders the development of NRR electrocatalysts. Herein, a series of Mo2C/MoO2 interface-engineered electrocatalysts with various Mo2C/MoO2 ratios were constructed by controlling the Y dosages. The controlled experimental results verified that the catalytic activity of NRR, the dosage of Y, and the ratio of Mo2C/MoO2 were strongly correlated. Density functional theory calculations show that the C-Mo-O coordination at the Mo2C/MoO2 interface can optimize the reaction path and reduce the energy barrier of the reaction intermediates, thereby enhancing the reaction kinetics of NRR.

Dinitrogen Activation within Frustrated Lewis Pairs Is Promoted by Adding External Electric Fields.

This study uses computational means to explore the feasibility of N2 cleavage by frustrated Lewis pair (FLPs) species. The employed FLP systems are phosphane/borane (1) and carbene/borane (2). Previous studies show that 1 and 2 react with H2 and CO2 but do not activate N2. The present study demonstrates that N2 is indeed inert, and its activation requires augmentation of the FLPs by an external tool. As we demonstrate here, FLP-mediated N2 activation can be achieved by an external electric field oriented along the reaction axis of the FLP. Additionally, the study demonstrates that FLP -N2 activation generates useful nitrogen compound, e.g., hydrazine (H2N-NH2). In summary, we conclude that FLP effectively activates N2 in tandem with oriented external electric fields (OEEFs), which play a crucial role. This FLP/OEEF combination may serve as a general activator of inert molecules.

A Bioinspired Copper-Pair Catalyst in Metal-Organic Frameworks for Molecular Dioxygen Activation and Aerobic Oxidative C-N Coupling.

Open Cu sites were loaded to the UiO-67 metal-organic framework (MOF) skeleton by introduction of flexible Cu-binding pyridylmethylamine (pyma) side chains to the biphenyldicarboxylate linkers. Distance between Cu centers in the MOF pores was tuned by controlling the density of metal-binding side chains. "Interacted" Cu-pair or "isolated" monomeric Cu sites were achieved with high and low (pyma)Cu side chain loading, respectively. Spectroscopic and theoretical studies indicate that "interacted" Cu pairs can effectively bind and activate molecular dioxygen to form Cu2O2 clusters, which showed high catalytic activity for aerobic oxidative C-N coupling. On the contrary, MOF catalyst bearing isolated monomeric Cu sites only showed modest catalytic activity. Enhancement in catalytic performance for the Cu-pair catalyst is attributed to the remote synergistic effect of the paired Cu site, which binds molecular dioxygen and cleaves the O═O bond in a collaborative manner. This work demonstrates that noncovalently interacted metal-pair sites can effectively activate inert small molecules and promote heterogeneous catalytic processes.

Catalytic hydrogenation reaction micro-kinetic model for dibenzyltoluene as liquid organic hydrogen carrier

The implementation of the liquid organic hydrogen carrier (LOHC) technology for efficient energy storage requires the development of a reliable kinetic model for both hydrogenation and dehydrogenation processes. In this research study, the catalytic hydrocarbon saturation for a dibenzyltoluene (DBT) mixture solution, containing dibenzylbenzene (DBB), dibenzylethylbenzene (DBEB) and impurities has been performed in the presence of Ru/Al2O3 particles. The influence of different reaction conditions, such as temperature, pressure, initial reactant concentration, catalyst amount and stirring speed has been examined. A measurement-based system micro-kinetics, based on the Langmuir–Hinshelwood mechanism with dissociative H2 surface adsorption, has been derived. H2 thermodynamic solubility equilibrium was defined through Henry's law. The adsorbing, desorption and reactivity of inert solvent molecules was not considered to be relevant. The mass transfer resistance over 1000 rpm stirring speed was negligible. Relative- and mean squared error of representation were 40.9% and 1.00×10−4, respectively. Expressions gave an excellent data prediction for the profile period trends with a relatively accurate estimation of H2 intermediates' rate selectivity, H2-covered area approximation and pathway rate-determining steps. Due to the lack of commercially available standard chemical compounds for quantitative analysis techniques, a novel experiment-based numerical calibration method was developed. Mean field (micro)kinetics represent an advancement in the mesoscale mechanistic understanding of physical interface phenomena. This also enables catalysis structure–activity relationships, unlocking the methodology for new LOHC reaching beyond traditional, such as ammonia, methanol and formate, which do not release H2 alone. Integrated multiscale simulations could include fluidics later on.

Electrocatalytic Conversion of Small Molecules Utilizing Concerted Proton-electron Transfer Mediators.

Activation of small molecules such as CO2, N2 or organic substrates and their subsequent transformation into complex value-added chemicals by electrocatalysis, utilizing renewable energy sources under ambient conditions, has gained considerable interest in the last few years. However, activation of these chemically inert molecules is hindered by their intrinsically high activation energy barrier presupposing the development of tailored catalytic systems, often precluding selective transformation to the desired target products. Recent studies have shown that the utilization of concerted proton-electron transfer (CPET) mediators (med-H) may facilitate these challenging electrocatalytic reactions.

Molecular simulation of competitive adsorption of CO2/N2/O2 gas in bituminous coal

The main cause of coal spontaneous combustion is the oxidation and temperature rise of coal. Injecting composite inert gas for fire prevention and extinguishing is one of the important methods to prevent coal spontaneous combustion. A large number of studies have macroscopically investigated the fire prevention and extinguishing effects of CO2/N2 and their synergistic actions. However, there is currently a lack of research at the molecular level on the competitive adsorption mechanism between mixed inert gases (CO2, N2) and O2 molecules in coal. Therefore, this study conducted adsorption experiments using Qian Yingzi(QYZ) bituminous coal and compared them with the simulation data of the Wiser coal model to verify the reliability of the Wiser model. Subsequently, employing grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods, the competitive adsorption behavior of different proportions of binary mixed component gases (CO2/O2, CO2/N2, O2/N2) at a temperature of 303.15 K was investigated from five perspectives: adsorption capacity, adsorption selectivity coefficient, potential energy distribution, competitive adsorption heat, and interaction energy. The results indicate that among the competitive component gases, CO2 exhibits the strongest adsorption effect on the entire system, which is closely correlated with the distribution range of adsorption energy sites. The adsorption heat and adsorption amount of CO2 consistently exhibit a negative correlation, whereas the relationship between the adsorption heat of N2 and O2 and the adsorption amount shows a positive correlation. Their adsorption capacities depend on the pressure and the proportion of the two gases. Based on the isothermal adsorption curve of CO2/N2, it is recommended that the gas pressure during actual inert gas injection be less than 2.5 MPa. Under this pressure, the competitive adsorption effect is no longer significant, providing a certain theoretical basis for high-pressure injection. Moreover, the preliminary determination of the optimal injection ratio range is from 4:6–3:7. Furthermore, a systematic logical framework for selecting underground inert gas composition is proposed, and an underground mobile inert gas infusion process is adopted. The actual gas composition for infusion is determined based on cost factors in practical engineering. The research results can provide guidance for the selection of gas injection parameters for mixed inert gas fire prevention and extinguishing in goaf.

A Unique Amorphous Porous BiSbOx Nanotube with Abundant Unsaturated Sb‐Stabilized BiO8−x Sites for Efficient CO2 Electroreduction in a Wide Potential Window

AbstractThe CO2 electroreduction reaction using sustainable electricity emerges as a viable strategy to produce high‐value‐added and profitable chemicals. The achievement of superior activity at a lower overpotential and higher selectivity in a wide potential window is vitally important for large‐scale industrial applications. Herein, a carbon‐composite amorphous porous BiSbOx nanotube with abundant unsaturated sites is reported to boost the conversion of CO2 to formate, exhibiting a formate selectivity of >90% in an extremely broad range of potentials from −0.5 to −1.4 V versus reversible hydrogen electrode (RHE) and a maximal energy conversion efficiency of 77.1%. Importantly, pure formic acid solution is directly obtained in a solid‐electrolyte cell for industrial‐scale applications. The porous tubular structure can expose more catalytic active sites, accelerate the mass transfer, and show fast surface charge transfer. Moreover, the unique coordination‐unsaturated Sb‐stabilized BiO8−x site can not only enhance the adsorption and activation of CO2 but also reasonably balance the stabilization and hydrogenation of *OCHO intermediate, thus leading to its obviously higher catalytic performance. As a result, a novel amorphous porous BiSbOx nanotube is successfully designed for efficient CO2 electroreduction, which may shed new light on developing many more amorphous composite metal oxide catalysts for conversion of inert small molecules.

Asymmetrical Interactions between Ni Single Atomic Sites and Ni Clusters in a 3D Porous Organic Framework for Enhanced CO2 Photoreduction.

3D porous organic frameworks, which possess the advantages of high surface area and abundant exposed active sites, are considered ideal platforms to accommodate single atoms (SAs) and metal nanoclusters (NCs) in high-performance catalysts; however, very little research has been conducted in this field. In the present work, a 3D porous organic framework containing Ni1 SAs and Nin NCs is prepared through the metal-assisted one-pot polycondensation of tetraaldehyde and hexaaminotriptycene. The single metal sites and metal clusters confined in the 3D space created a favorable micro-environment that facilitated the activation of chemically inert CO2 molecules, thus promoting the overall photoconversion efficiency and selectivity of CO2 reduction. The 3D-NiSAs/NiNCs-POPs, as a CO2 photoreduction catalyst, demonstrated an exceptional CO production rate of 6.24mmolg-1h-1, high selectivity of 98%, and excellent stability. The theoretical calculations uncovered that asymmetrical interaction between Ni1 SAs and Nin NCs not only favored the bending of CO2 molecules and reducing the CO2 reduction energy, but also regulated the electronic structure of the catalyst leading to the optimal binding strength of intermediates.

Unraveling the deactivation mechanism of Co-LiH composite catalyst for ammonia synthesis at milder conditions

An efficient ammonia synthesis catalyst that operates under mild conditions has been a long-cherished goal in heterogeneous catalysis. The challenges associated with low-temperature ammonia synthesis arise from both the activation of inert N2 molecules and the presence of scaling relations between reactant dissociation and intermediate adsorption energies. Transition metals-metal hydride (TM-MH) composite catalysts have shown promise to overcome these challenges as both TM and MH actively participate in the reaction, enabling improved ammonia synthesis rates at lower temperatures (150 ºC). Considering this prospect, two types of Co-LiH catalyst were synthesized by ball-milling of precursors (CoCl2 and LiH- denoted as Co-LiH(rxn)) and pure components (Co and LiH- denoted as Co-LiH(pur)), and their catalytic activity was evaluated at several reaction conditions to investigate the stability for long-term operation. Co-LiH(rxn) was found to deactivate in less than 150 h whereas Co-LiH(pur) displayed a continuous production although the synthesis rate was 3 times lower than the former. Structural characterization techniques, such as XRD, SEM, and TEM were used, and it was found that Co metal in the FCC phase was primarily sintered due to its small particle size in the fresh catalyst. Temperature-programmed desorption (TPD) test on the spent Co-LiH(rxn) catalyst also displayed an ammonia release profile similar to that of LiNH2 decomposition, which confirms the presence of ammonia in the spent catalyst structure. Hence, another major finding is speculated that irreversible ammonia absorption by LiH at the target ammonia reaction conditions contributes to the deactivation of the catalyst and the formation of intermediate compounds that are required for continuous ammonia generation in this composite catalyst.