NH3 Production Research Articles

Facile synthesis of coral-like nitrogen and sulfur co-doped carbon-encapsulated FeS2 for efficient electroreduction of nitrate to ammonia

Electro-reduction of nitrate (NO3–) to ammonia is a promising method to transform the environmental contaminant NO3– to value-added ammonia. Since diverse end-products might be formed and a convenient material preparation process is preferable, it is of great importance to facilely synthesize a high-performance electro-catalyst towards ammonia generation with high selectivity. Herein, a coral-like nitrogen (N) and sulfur (S) co-doped carbon-encapsulated FeS2 composite material (FeS2@NSC) was successfully fabricated for effective electro-reduction of high-concentration of NO3– to ammonia through a simple one-step pyrolysis method. The FeS2@NSC-400 material exhibited remarkable electrocatalytic NH3 production performance with the NH3 yield of 4428.35 μg h−1 cm−2 and NH3 Faraday efficiency of 84.75 % at −1.4 V vs. Ag/AgCl, which outperforms many of the reported electrocatalysts. The unique small cluster coral-like core–shell structure, N, S co-doping and the interaction between inner FeS2 and the outer carbon layer greatly enhanced the electrical conductivity and stability of the material and the adsorption of NO3– and intermediate products, thereby facilitating the electrocatalytic performance of nitrate-to-ammonia. The FeS2@NSC material induced the electrocatalytic reduction of NO3– mainly through direct electron transfer instead of the indirect atomic H* mediation, and the main reduction product NH3 was speculated to derive from the pathway of NO3–* → NO2–* → NO* → HNO* → H2NO* → H2NOH* → NH3.

Experimental Protocols for Sustainable Ammonia Production by Photocatalytic Nitrogen Fixation: Pitfalls and Remedial Measures

AbstractThe synthesis of ammonia (NH3) by photocatalytic nitrogen (N2) fixation has gained tremendous attention from researchers worldwide. The number of reports on different materials for photocatalytic N2 fixation is increasing year by year in the quest for developing breakthrough and sustainable photocatalysts in this field. However, there are several pitfalls (nitrogenous impurities in feed gas and on the surface of the catalyst, reaction conditions, use of scavengers, NH3 quantification methods, etc.) in the path of photocatalytic N2 fixation experiments, which can lead to the reporting of bogus NH3 production rates. Therefore, the use of accurate experimental protocols for the quantification of photogenerated NH3 requires immediate attention and focus of the researchers so that reliable data can be reported in the literature. This perspective article mainly focuses on generating awareness in the photocatalytic N2 fixation research community about the recent establishments for reporting experimental results in this field. Several pitfalls that may lead to the wrong data reporting and remedial measures to avoid them are discussed in detail. Finally, a summary of the recent advancements in this field and recommendations on future directions is provided.

The effect of the oxygen storage material on a three-way catalyst spatio-temporally resolved with Spaci-MS

A methodology that allows the estimation of the stored oxygen (oxygen storage capacity (OSC)) along the TWC catalyst length by spatio-temporally resolving the O2 profiles during rich to lean cycle conditions with the use of the Spaci-MS technique has been developed. As a case study, the effect of the presence of mixed cerium-zirconium oxide as oxygen storage material has been investigated. The oxygen storage capacity for the TWC containing Ce material was much higher than without. The study also explores the reaction pathways typical of TWC along the catalyst coordinates by spatio-temporally resolving O2, H2, CO, and NO, as well as the related products and intermediates providing important understanding on, for example, the water-gas shift reaction leading to H2 production and how they develop differently depending on the OSM (oxygen storage material) in the catalyst. H2 production occurs closer to the front of the TWC length in the case of the catalyst without Ce, and results in an earlier production of undesired NH3 from NO reaction with H2. However, more N2O has been observed for the catalyst with Ce, which suggests the catalyst composition could be optimised to minimize overall secondary emissions.

Lithium‐Mediated Nitrogen Reduction for Ammonia Synthesis: Reviewing the Gap between Continuous Electrolytic Cells and Stepwise Processes through Galvanic Li─N2 Cells

AbstractElectrochemical N2 reduction reaction (E‐NRR) has recently gained increasing interest within the scientific community, due to the ongoing energy crisis and pursuit of process sustainability. In this scenario, emerging lithium‐mediated (Li‐m) strategies are obtaining promising Faradaic efficiency (FE) and NH3 production rate values. In this work, the Li‐m scenarios are classified and explained toward a more sustainable process. Continuous processes, with a lithium salt and a proton donor in an electrolytic cell, are analyzed and compared with stepwise pathways. Different parameters are summarized in relation to the system stability, for which the importance of a tailored solid electrolyte interphase (SEI) layer emerged. Among stepwise processes, the thermochemical direct nitridation of lithium is discussed together with the recently developed Galvanic Li─N2 cell strategy.

Hot Carrier Controlled Nitrogen Fixation Reaction in Metal-Free Boron-Anchored Aza-COF: Insight from Nonadiabatic Molecular Dynamics Simulation.

Designing highly efficient photocatalysts for the production of renewable energy is a challenging task that necessitates simultaneous control of chemical activity and photocarrier dynamics for a particular reaction. To this end, we have investigated the catalytic mechanism and real-time photocarrier dynamics of the nitrogen reduction reaction (NRR) at the metal-free boron-functionalized 2D aza-COF (B-aza-COF), an inexpensive and environmentally friendly semiconductor. By employing density functional theory (DFT) and time-dependent ab initio nonadiabatic molecular dynamics simulation, we have investigated the electronic structure, light harvesting ability, free energy change, and dynamics of photoexcited carriers. Our calculated results reveal that the gas phase N2 molecule can be effectively reduced into NH3 on B-aza-COF under UV-visible light. Therefore, our investigation on the design of efficient photocatalysts for the nitrogen reduction reaction (NRR) provides a cost-effective opportunity for the sustainable production of NH3.

Reactive Force Field Molecular Dynamics Investigation of NH3 Generation Mechanism during Protein Pyrolysis Process.

The mechanism of ammonia formation during the pyrolysis of proteins in biomass is currently unclear. To further investigate this issue, this study employed the AMS 2023.104 software to select proteins (actual proteins) as the model compounds and the amino acids contained within them (assembled amino acids) as the comparative models. ReaxFF molecular dynamics simulations were conducted to explore the nitrogen transformation and NH3 generation mechanisms in three-phase products (char, tar, and gas) during protein pyrolysis. The research results revealed several key findings. Regardless of whether the model compounds are actual proteins or assembled amino acids, NH3 is the primary nitrogen-containing product during pyrolysis. However, as the temperature rises to higher levels, such as 2000 K and 2500 K, the amount of NH3 decreases significantly in the later stages of pyrolysis, indicating that it is being converted into other nitrogen-bearing species, such as HCN and N2. Simultaneously, we also observed significant differences between the pyrolysis processes of actual proteins and assembled amino acids. Notably, at 2000 K, the amount of NH3 generated from the pyrolysis of assembled amino acids was twice that of actual proteins. This discrepancy mainly stems from the inherent structural differences between proteins and amino acids. In proteins, nitrogen is predominantly present in a network-like structure (NH-N), which shields it from direct external exposure, thus requiring more energy for nitrogen to participate in pyrolysis reactions, making it more difficult for NH3 to form. Conversely, assembled amino acids can release NH3 through a simpler deamination process, leading to a significant increase in NH3 production during their pyrolysis.

Efficient ammonia synthesis from the air using tandem non-thermal plasma and electrocatalysis at ambient conditions

While electrochemical N2 reduction presents a sustainable approach to NH3 synthesis, addressing the emission- and energy-intensive limitations of the Haber-Bosch process, it grapples with challenges in N2 activation and competing with pronounced hydrogen evolution reaction. Here we present a tandem air-NOx-NOx−-NH3 system that combines non-thermal plasma-enabled N2 oxidation with Ni(OH)x/Cu-catalyzed electrochemical NOx− reduction. It delivers a high NH3 yield rate of 3 mmol h−1 cm−2 and a corresponding Faradaic efficiency of 92% at −0.25 V versus reversible hydrogen electrode in batch experiments, outperforming previously reported ones. Furthermore, in a flow mode concurrently operating the non-thermal plasma and the NOx− electrolyzer, a stable NH3 yield rate of approximately 1.25 mmol h−1 cm−2 is sustained over 100 h using pure air as the intake. Mechanistic studies indicate that amorphous Ni(OH)x on Cu interacts with hydrated K+ in the double layer through noncovalent interactions and accelerates the activation of water, enriching adsorbed hydrogen species that can readily react with N-containing intermediates. In situ spectroscopies and density functional theory (DFT) results reveal that NOx− adsorption and their hydrogenation process are optimized over the Ni(OH)x/Cu surface. This work provides new insights into electricity-driven distributed NH3 production using natural air at ambient conditions.

Revealing the nitrogen migration mechanism during pyrolysis and steam gasification of biomass: A combined ReaxFF MD and DFT study

The biomass pyrolysis/gasification technology takes advantages of high efficiency and carbon neutrality, which is promising for high value-added products fabrication. However, biomass possesses relatively high amount of N especially for seaweeds and municipal sludge wastes, and the lack of N migration mechanism has resulted in emission of N-containing pollutants and limited its industrial application. In this work, a simulation investigation combining reactive force field molecular dynamic and density functional theory calculations was performed to study the conversion mechanisms of N-containing species in the pyrolysis/gasification of biomass processes. The glutamic acid and cellulose were selected as the model compounds of N-containing and typical compositions of biomass, respectively, and six models containing multiple mass ratios of glutamic acid to cellulose and steam to feedstock were constructed. The results show that the majority of nitrogen in the original model is converted towards NH3-N (62%) during glutamic acid pyrolysis by direct cleavage, hydrogen capture, deamination, and decarboxylation. The presence of cellulose effectively inhibits the decomposition of NH3 at high temperature range, thereby increasing the yield of NH3-N (up to 70%) and restraining the conversion of nitrogen into mesomolecules. The introduction of H2O provides a substantial amount of •H radicals, which facilitates the conversion of nitrogen into NH3-N. During DFT calculations, eight reaction pathways for the formation of N-containing products were proposed on the basis of distribution of pyrolysis products. The glutamic acid cleavage reaction achieves the lowest energy barrier, and the deamination of glutamic acid towards a ternary cyclic ether is found to be the most feasible pathway for the NH3 production. This work can provide theoretical support for nitrogen pollutants mitigation during pyrolysis and steam gasification of biomass processes.

Catalytic Ammonia Formation in a Microreaction Chamber with Electrically Intensified Arc Plasma

AbstractAmmonia (NH3) production is of global concern for today's food supply security and as future energy vector. Plasma technology can add to supply‐chain resilience of fertilizer production and improve the environmental profile using renewable energy; allowing distributed NH3 production. With the objective to provide process intensification of small‐capacity reactors for local supply, a novel micropyramid‐disk plasma reactor operated in micro‐arc mode was developed. NH3 was synthesized from N2, nitrogen, and H2, hydrogen over Ru/MCM‐41 catalyst at atmospheric pressure. The microplasma brings plasma and catalyst surface close together and intensifies the electric field. The arc plasma elevates temperature, ‘nonthermal’, releasing high‐energy free electrons, known to be effective in converting low‐reactive molecules. The study demonstrates that microplasma, with reduced electrode‐to‐electrode dimensions and a microstructured reaction environment, enhances the performance of the NH3 synthesis and opens novel process windows. This is detailed on the impact of feed ratio (N2/H2), applied voltage, frequency, electrode gap, and the flow distribution by which the gas is fed in. Optical emission spectroscopy (OES) was used to identify vibrationally and other excited species generated by the microplasma and confirms the catalyst is in symbiosis with the radicals.

In-situ assembling novel N-Ti3C2/BiOClxBr1−x composites with enhanced photocatalytic degradation and nitrogen reduction activity

Herein, a collection of novel N-Ti3C2/BiOClxBr1−x composites are fabricated via a simple in-situ sonochemical process. Not only the preparation method for N-Ti3C2 but also the photocatalytic system of N-Ti3C2/BiOClxBr1−x are firstly developed. Multiple characterizations jointly demonstrate the successful fabrication of the composites. Compared to that of BiOClxBr1−x, the maximum improvements of 1.16, 1.25 and 1.26 folds are severally confirmed for the photocatalytic degradation of levofloxacin, Rhodamine B, and methylene blue over N-Ti3C2/BiOClxBr1−x composites. In addition, through radicals trapping tests, the primary active species in photocatalytic degradation process are verified to be O2−. Moreover, N-Ti3C2/BiOClxBr1−x composites also exhibit 1.18 and 1.14 times enhancements for NH3 production compared with that of BiOClxBr1−x with or without the presence of methanol, respectively. In addition, the maximum improvements of photo-current and photo-potential for BiOClxBr1−x are 1.29 and 1.86 folds with the introduction of N-Ti3C2, respectively. The enhanced photocatalytic activity of N-Ti3C2/BiOClxBr1−x composites is owing to the heightened light absorption, increased specific surface area, and accelerated separation of photoinduced carriers. Additionally, the stable photocatalytic properties of N-Ti3C2/BiOClxBr1−x are confirmed by three photocatalytic recycle tests on pollutant degradation and nitrogen reduction combined with X-ray diffraction patterns before and after three recycles. This study suggests that N-Ti3C2 is an efficient ornamentation for boosting photocatalytic activity ofBiOClxBr1−x, which can also be expanded as a promising modifier for other semiconductors.

Oxygen vacancy optimization of the titanium carbide MXene surface for enhanced electrochemical nitrogen reduction

Electrochemical N2 reduction reaction (NRR) provides a hopeful way for sustainable NH3 production. It is the key to realize efficient NRR reaction to optimize the structure and electronic configuration of catalyst materials. Increasing the number of active centers in Ti3C2Tx MXene allows for the development of effective NRR electrocatalysts. Herein, we rationally integrated defect engineering to create oxygen vacancy-rich Ti3C2-MXene (K-Ti3C2-400) as an efficient NRR catalyst with an NH3 yield of 32.25 ± 0.8 μg·h−1·mg−1cat. at − 0.55 V and a Faradaic efficiency of 12.85 % ± 0.26 % at −0.45 V versus reversible hydrogen electrode. According to the density functional theory, oxygen vacancies can prevent the hydrogen evolution reaction by delaying H adsorption, thereby activating absorbed N2 and encouraging *N2H synthesis. This research opens up new possibilities for creating MXene-based catalysts with surface reactivity and selectivity for electrochemical N2 fixation.

Unlocking sustainable nitrate reduction: Earth-abundant bimetallic electrodes under galvanostatic evaluation

Electrochemical reduction of nitrate (ERN) has emerged as a green alternative to alleviate the NH3 production via the Haber-Bosch process. Harnessing earth-abundant materials for electrocatalysts is a logical strategy, minimizing dependence on the cost-prohibitive platinum group elements. While previous research has delved into the preparation and evaluation of electrodes for NH3 generation, much of it has been mainly focused on potentiostatic conditions and mechanisms elucidation, overlooking real-world scenarios and precluding the advancement towards technology implementation. This study addresses this gap by screening the performance of earth-abundant bimetallic electrodes, leveraging Cu foam as a substrate and modifying it with Cu2O, Ni(OH)2, SnO2, and Co(OH)x through electrodeposition. A comprehensive characterization encompassing morphological, structural, and electrochemical analysis was performed on the novel bimetallic surfaces. Electrolysis experiments targeting 30 mg L−1 NO3−-N were conducted under galvanostatic conditions (2.5, 5, 10, 20, and 40 mA cm−2), revealing the following trend in NH3 yield (mmol NH3 gcat−1 h−1): Cu/Co(OH)x > Cu/Cu2O > Cu foam > Cu/SnO2 > Cu/Ni(OH)2. Engineering figures of merit required for techno-economic analysis, such as Faradic efficiency, electrical energy per order, kinetic constants, and NH3 generation efficiency, were estimated for each configuration. This study not only sheds light on the operational conditions of ERN but also offers a roadmap toward sustainable and economically viable NH3 production.

Regulating concentration of surface oxygen vacancies in Bi2MoO6/Bi-MOF for boosting photocatalytic ammonia synthesis

Surface oxygen vacancies (OVs) engineering has been widely adopted as an effective strategy to enhance photocatalytic performance. At present, photocatalytic systems capable of precisely regulating surface OVs concentrations, which could help illuminate the effects of the surface OVs concentration on N2 fixation activity, are still scarce. Herein, bismuth-based metal organic framework (Bi-MOF) was loaded onto the surface of Bi2MoO6 (BMO) as an operable platform, and the OVs concentration in the Bi-MOF component of BMO/Bi-MOF could be regulated by reduction of bismuth ions therein. Experimental results confirm that optimum construction of OVs in the Bi-MOF promotes the photoelectrons transfer from BMO to Bi-MOF, facilitating the activation of N2 at OVs. Consequently, the optimized catalyst shows superior performance in NH3 production, which reaches 125.78 μmol h−1 g−1, 21.4 higher than that of BMO. This work underline the significance of regulating surface OVs concentration, providing inspiration for the development of efficient OVs-modified photocatalysts.

Interlinking electronic band properties in catalysts with electrochemical nitrogen reduction performance: a direct influence

Abstract The wordwide energy demands and the surge towards a net-zero sustainable society let the researchers set a goal towards the end of carbon cycle. This has enormously exaggerated the electrocatalytic processes such as water splitting, CO2 capture and reduction and nitrogen reduction reaction (NRR) as a safe and green alternative as these involve the utilization of renewable green power. Interestingly, the NH3 produced from NRR has been realized as a future fuel in terms of safer green H2 storage and transportation. Nevertheless, to scale up the NH3 production electrochemically, a benevolent catalyst needs to be developed. More interestingly, the electronic features of the catalyst that actually contribute to the interaction and binding between the adsorbate and reaction intermediates should be analyzed such that these can be tuned based on our requirements to obtain the desired high-standard goals of NH3 synthesis. The current topical review aims to provide an illustrative understanding on the experimental and theoretical descriptors that are likely to influence the electronic structure of catalysts for NRR. We have widely covered a detailed explanation regarding work function, d-band center and electronic effect on the electronic structures of the catalysts. While summarizing the same, we realized that there are several discrepancies in this field, which have not been discussed and could be misleading for the newcomers in the field. Thus, we have briefed the limitations and diverging explanations and have provided a few directions that could be looked upon to overcome the issues.

Hepatic ketone body regulation of renal gluconeogenesis

ObjectivesDuring fasting, liver pivotally regulates blood glucose levels through glycogenolysis and gluconeogenesis. Kidney also produces glucose through gluconeogenesis. Gluconeogenic genes are transactivated by fasting, but their expression patterns are chronologically different between the two organs. We find that renal gluconeogenic gene expressions are positively correlated with the blood β-hydroxybutyrate concentration. Thus, we herein aim to investigate the regulatory mechanism and its physiological implications. MethodsGluconeogenic gene expressions in liver and kidney were examined in hyperketogenic mice such as high-fat diet (HFD)-fed and ketogenic diet-fed mice, and in hypoketogenic PPARα knockout (PPARα−/−) mice. Renal gluconeogenesis was evaluated by rise in glycemia after glutamine loading in vivo. Functional roles of β-hydroxybutyrate in the regulation of renal gluconeogenesis were investigated by metabolome analysis and RNA-seq analysis of proximal tubule cells. ResultsRenal gluconeogenic genes were transactivated concurrently with blood β-hydroxybutyrate uprise under ketogenic states, but the increase was blunted in hypoketogenic PPARα−/− mice. Administration of 1,3-butandiol, a ketone diester, transactivated renal gluconeogenic gene expression in fasted PPARα−/− mice. In addition, HFD-fed mice showed fasting hyperglycemia along with upregulated renal gluconeogenic gene expression, which was blunted in HFD-fed PPARα−/− mice. In vitro experiments and metabolome analysis in renal tubular cells showed that β-hydroxybutyrate directly promotes glucose and NH3 production through transactivating gluconeogenic genes. In addition, RNA-seq analysis revealed that β-hydroxybutyrate-induced transactivation of Pck1 was mediated by C/EBPβ. ConclusionsOur findings demonstrate that β-hydroxybutyrate mediates hepato–renal interaction to maintain homeostatic regulation of blood glucose and systemic acid-base balance through renal gluconeogenesis regulation.

Flexible Green Ammonia Production Plants: Small-Scale Simulations Based on Energy Aspects

The conventional Haber–Bosch process (HBP) for NH3 production results in CO2 emissions of almost 400 Mt/y and is responsible for 1–2% of global energy consumption; furthermore, HBP requires large-scale industrial equipment. Green or e-ammonia produced with hydrogen from alkaline water electrolysis using renewable energy and nitrogen from the air is considered an alternative to fossil-fuel-based ammonia production. Small-scale plants with the distributed on-site production of e-ammonia will begin to supplant centralized manufacturing in a carbon-neutral framework due to its flexibility and agility. In this study, a flexible small-scale NH3 plant is analyzed with respect to three steps—H2 generation, air separation, and NH3 synthesis—to understand if milder operating conditions can benefit the process. This study investigates the aspects of flexible small-scale NH3 plants powered by alkaline electrolyzer units with three specific capacities: 1 MW, 5 MW, and 10 MW. The analysis is carried out through Aspen Plus V14 simulations, and the primary criteria for selecting the pressure, temperature, and number of reactors are based on the maximum ammonia conversion and minimum energy consumption. The results show that: (i) the plant can be operated across a wide range of process variables while maintaining low energy consumption and (ii) alkaline electrolysis is responsible for the majority of energy consumption, followed by the ammonia synthesis loop and the obtention of N2, which is negligible.

Sunlight-Driven Nitrate-to-Ammonia Reduction with Water by Iron Oxyhydroxide Photocatalysts.

The photocatalytic reduction of harmful nitrates (NO3-) in strongly acidic wastewater to ammonia (NH3) under sunlight is crucial for the recycling of limited nitrogen resources. This study reports that a naturally occurring Cl--containing iron oxyhydroxide (akaganeite) powder with surface oxygen vacancies (β-FeOOH(Cl)-OVs) facilitates this transformation. Ultraviolet light irradiation of the catalyst suspended in a Cl--containing solution promoted quantitative NO3--to-NH3 reduction with water under ambient conditions. The photogenerated conduction band electrons promoted the reduction of NO3--to-NH3 over the OVs. The valence band holes promoted self-oxidation of Cl- as the direct electron donor and eliminated Cl- was compensated from the solution. Photodecomposition of the generated hypochlorous acid (HClO) produced O2, facilitating catalytic reduction of NO3--to-NH3 with water as the electron donor in the entire system. Simulated sunlight irradiation of the catalyst in a strongly acidic nitric acid (HNO3) solution (pH ∼ 1) containing Cl- stably generated NH3 with a solar-to-chemical conversion efficiency of ∼0.025%. This strategy paves the way for sustainable NH3 production from wastewater.

Promoting nitrogen photofixation for the synthesis of ammonia using oxygen-vacant Fe2O3/ZrO2 visible light photocatalyst with straddling heterojunction and enhanced charge transfer

Photocatalytic nitrogen (N2) fixation is a promising and environmentally friendly alternative approach to the energy-intensive Haber-Bosch process to produce green ammonia (NH3) with zero carbon emissions. However, the unique setbacks rest on developing an active photocatalyst with an accelerated charge transfer that could efficiently adsorb and activate the chemically inert N2 into useful NH3. Herein, an oxygen-vacant Fe2O3/ZrO2 photocatalyst with straddling heterojunction was successfully synthesised by the hydrothermal method followed by calcination at 450 °C. The addition of oxygen vacancy-inducing ferromagnetic material on ZrO2 increased the adsorption and activation of N2, broadened the solar absorption window (680 nm extending to 910 nm). It also accelerated light-induced charge separation of the photocatalyst thereby greatly enhancing the production of NH3 (1.301 mmol h−1 g−1) with about a 7-fold increase in comparison to ZrO2 at ambient conditions under sunlight irradiation. This work therefore sheds light on the effect of oxygen vacancies and the flow of charge carriers in the effective photofixation of N2 to NH3 synthesis through a sustainable route.

Bias-free solar NH3 production by perovskite-based photocathode coupled to valorization of glycerol

Bias-free solar NH3 production by perovskite-based photocathode coupled to valorization of glycerol

Characterization of the H2/NOx reaction process over the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst

An excellent textual properties and performance La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst was synthesized. The reaction mechanism of H2/NOx over the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst was investigated by temperature programmed reduction/ desorption/ surface reaction (TPR/D/SR) technologies and in-situ diffuse reflectance Fourier transform (DRIFT) technology. The results show that cerium or palladium species are inserted into the cells of LaCoO3, as well as they synergetic promote the redox properties of the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst. Surface activated nitrates exist over the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst, with thermal stable increasing in the order: absorbed N2O4 < monodentate nitrates < chelating bidentate nitrates < nitrates unidentate < free ionic nitrates < bulk free ionic nitrates. H2 preferentially reacted with absorbed N2O4 and monodentate nitrates at low temperatures, due to their high activity. The concentration of generated NH3 from the redox reaction of H2/NOx achieves the maximum value between 350 and 450 °C over the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst. Compared with the NOx adsorption process at 50 °C, monodentate nitrates and absorbed N2O4 disappeared due to their low thermal stability, chelating bidentate nitrates become stronger, as well as free ionic nitrates converted to bulk free ionic nitrates with higher thermal stability at 350 °C. When H2 is exposed to NOx species adsorbed on La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3, chelating bidentate nitrates and bulk free ionic nitrates are consumed gradually, indicating that although the bulk free ionic nitrates own high stability, it also could be consumed by involving in the H2/NOx reaction at 350 °C. The quantitative H2/NO reaction experiments confirmed the results of H2-TPSR and NSR. It is beneficial to the formation of NH3 when the H2/NO ratio is more than 2.5. Comparing traditional Pt-BaO/Al2O3 catalyst, the La0.9Ce0.1Co0.9Pd0.1O3-BaO/Al2O3 catalyst exhibit an excellent performance, including considerable NH3 production property, lower N2O selectivity, and the precious metal saving.