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Single-atom catalysts (SACs) have attracted significant attention because they exhibit unique catalytic performance due to their ideal structure. However, maintaining atomically dispersed metal under high temperature, while achieving high catalytic activity remains a formidable challenge. In this work, we stabilize single platinum atoms within sub-nanometer surface cavities in well-defined 12CaO·7Al 2 O 3 (C12A7) crystals through theoretical prediction and experimental process. This approach utilizes the interaction of isolated metal anions with the positively charged surface cavities of C12A7, which allows for severe reduction conditions up to 600 °C. The resulting catalyst is stable and highly active toward the selective hydrogenation of nitroarenes with a much higher turnover frequency (up to 25772 h −1 ) than well-studied Pt-based catalysts. The high activity and selectivity result from the formation of stable trapped single Pt atoms, which leads to heterolytic cleavage of hydrogen molecules in a reaction that involves the nitro group being selectively adsorbed on C12A7 surface. Stabilize the active metal single atoms under harsh conditions is critical for the development of single atom catalysts. Here the authors report a nanoporous crystal, 12CaO·7Al 2 O 3 , that can firmly stabilize Pt single atoms in its surface cavities for efficient catalytic hydrogenation of nitroarenes.

Ammonia (NH 3 ) is pivotal to the fertilizer industry and one of the most commonly produced chemicals 1 . The direct use of atmospheric nitrogen (N 2 ) had been challenging, owing to its large bond energy (945 kilojoules per mole) 2 , 3 , until the development of the Haber–Bosch process. Subsequently, many strategies have been explored to reduce the activation barrier of the N≡N bond and make the process more efficient. These include using alkali and alkaline earth metal oxides as promoters to boost the performance of traditional iron- and ruthenium-based catalysts 4 – 6 via electron transfer from the promoters to the antibonding bonds of N 2 through transition metals 7 , 8 . An electride support further lowers the activation barrier because its low work function and high electron density enhance electron transfer to transition metals 9 , 10 . This strategy has facilitated ammonia synthesis from N 2 dissociation 11 and enabled catalytic operation under mild conditions; however, it requires the use of ruthenium, which is expensive. Alternatively, it has been shown that nitrides containing surface nitrogen vacancies can activate N 2 (refs. 12 – 15 ). Here we report that nickel-loaded lanthanum nitride (LaN) enables stable and highly efficient ammonia synthesis, owing to a dual-site mechanism that avoids commonly encountered scaling relations. Kinetic and isotope-labelling experiments, as well as density functional theory calculations, confirm that nitrogen vacancies are generated on LaN with low formation energy, and efficiently bind and activate N 2 . In addition, the nickel metal loaded onto the nitride dissociates H 2 . The use of distinct sites for activating the two reactants, and the synergy between them, results in the nickel-loaded LaN catalyst exhibiting an activity that far exceeds that of more conventional cobalt- and nickel-based catalysts, and that is comparable to that of ruthenium-based catalysts. Our results illustrate the potential of using vacancy sites in reaction cycles, and introduce a design concept for catalysts for ammonia synthesis, using naturally abundant elements. Ammonia is synthesized using a dual-site approach, whereby nitrogen vacancies on LaN activate N 2 , which then reacts with hydrogen atoms produced over the Ni metal to give ammonia.

Novel approaches to efficient ammonia synthesis at an ambient pressure are actively sought out so as to reduce the cost of ammonia production and to allow for compact production facilities. It is accepted that the key is the development of a high-performance catalyst that significantly enhances dissociation of the nitrogen–nitrogen triple bond, which is generally considered a rate-determining step. Here we examine kinetics of nitrogen and hydrogen isotope exchange and hydrogen adsorption/desorption reactions for a recently discovered efficient catalyst for ammonia synthesis—ruthenium-loaded 12CaO·7Al 2 O 3 electride (Ru/C12A7:e − )—and find that the rate controlling step of ammonia synthesis over Ru/C12A7:e − is not dissociation of the nitrogen–nitrogen triple bond but the subsequent formation of N–H n species. A mechanism of ammonia synthesis involving reversible storage and release of hydrogen atoms on the Ru/C12A7:e − surface is proposed on the basis of observed hydrogen absorption/desorption kinetics. Development of catalysts that enhance dissociation of the nitrogen–nitrogen triple bond will reduce costs of ammonia production. Here, the authors study ammonia synthesis over a ruthenium loaded electride catalyst and show that the rate-determining step is shifted to nitrogen–hydrogen bond formation.

Industrially, the artificial fixation of atmospheric nitrogen to ammonia is carried out using the Haber–Bosch process, but this process requires high temperatures and pressures, and consumes more than 1% of the world's power production. Therefore the search is on for a more environmentally benign process that occurs under milder conditions. Here, we report that a Ru-loaded electride [Ca 24 Al 28 O 64 ] 4+ (e − ) 4 (Ru/C12A7:e − ), which has high electron-donating power and chemical stability, works as an efficient catalyst for ammonia synthesis. Highly efficient ammonia synthesis is achieved with a catalytic activity that is an order of magnitude greater than those of other previously reported Ru-loaded catalysts and with almost half the reaction activation energy. Kinetic analysis with infrared spectroscopy reveals that C12A7:e − markedly enhances N 2 dissociation on Ru by the back donation of electrons and that the poisoning of ruthenium surfaces by hydrogen adatoms can be suppressed effectively because of the ability of C12A7:e − to store hydrogen reversibly. Methods that fix atmospheric nitrogen to ammonia under mild conditions could offer a more environmentally benign alternative to the Haber–Bosch process. Now, a Ru-loaded electride, [Ca 24 Al 28 O 64 ] 4+ (e − ) 4 , is reported that acts as an efficient electron donor and reversible hydrogen store, and is demonstrated to function as an efficient catalyst for ammonia synthesis.

Activating high-energy multiple bonds using earth-abundant metals is one of the most significant challenges in catalysis. Here, we show that LaCoSi—a ternary intermetallic compound—is an efficient and stable catalyst for N 2 activation to produce NH 3 . The ammonia synthesis is significantly promoted by shifting the reaction bottleneck from the sluggish N 2 dissociation to NH x formation, which few catalysts have achieved. Theoretical calculations reveal that the negatively charged cobalt mediates electron transfer from lanthanum to the adsorbed N 2 , which further reduces the activation barrier of N 2 dissociation. Most importantly, the specific LaCoSi geometric configuration stabilizes the N 2 adsorption with a strong exothermic effect, which dramatically decreases the apparent energy barrier of N 2 activation. Consequently, LaCoSi shows a superior activity (1,250  μ mol g −1  h −1 ), with a 60-fold increase over the activity of supported cobalt catalysts under mild reaction conditions (400  ° C, 0.1 MPa). Ammonia synthesis is an energy-intensive process due to the high activation barrier for N 2 dissociation. Here, Hosono and co-workers show that the intermetallic compound LaCoSi can lower the energy requirement for N 2 activation and shift the rate-determining step of the process to NH x formation under mild conditions.

The tunability of reaction pathways is required for exploring efficient and low cost catalysts for ammonia synthesis. There is an obstacle by the limitations arising from scaling relation for this purpose. Here, we demonstrate that the alkali earth imides ( Ae NH) combined with transition metal (TM = Fe, Co and Ni) catalysts can overcome this difficulty by utilizing functionalities arising from concerted role of active defects on the support surface and loaded transition metals. These catalysts enable ammonia production through multiple reaction pathways. The reaction rate of Co/SrNH is as high as 1686.7 mmol·g Co −1 ·h −1 and the TOFs reaches above 500 h −1 at 400 °C and 0.9 MPa, outperforming other reported Co-based catalysts as well as the benchmark Cs-Ru/MgO catalyst and industrial wüstite-based Fe catalyst under the same reaction conditions. Experimental and theoretical results show that the synergistic effect of nitrogen affinity of 3d TMs and in-situ formed NH 2− vacancy of alkali earth imides regulate the reaction pathways of the ammonia production, resulting in distinct catalytic performance different from 3d TMs. It was thus demonstrated that the appropriate combination of metal and support is essential for controlling the reaction pathway and realizing highly active and low cost catalysts for ammonia synthesis. The presence of electrically active defects on the surface of the support has been shown to be effective for N 2 activation. Here the authors discover that electron-rich polyanionic NH 2− defect allows for efficient ammonia synthesis via multiple reaction pathway by incorporating various affordable transition metals.

Suzuki cross-coupling reactions catalyzed by palladium are powerful tools for the synthesis of functional organic compounds. Excellent catalytic activity and stability require negatively charged Pd species and the avoidance of metal leaching or clustering in a heterogeneous system. Here we report a Pd-based electride material, Y 3 Pd 2 , in which active Pd atoms are incorporated in a lattice together with Y. As evidenced from detailed characterization and density functional theory (DFT) calculations, Y 3 Pd 2 realizes negatively charged Pd species, a low work function and a high carrier density, which are expected to be beneficial for the efficient Suzuki coupling reaction of activated aryl halides with various coupling partners under mild conditions. The catalytic activity of Y 3 Pd 2 is ten times higher than that of pure Pd and the activation energy is lower by nearly 35%. The Y 3 Pd 2 intermetallic electride catalyst also exhibited extremely good catalytic stability during long-term coupling reactions. In Suzuki coupling reactions, excellent catalytic performance require negatively charged Pd species and the avoidance of metal leaching or clustering. Here the authors implanted Pd sites into an intermetallic electride, Y 3 Pd 2 , which serves as an efficient and stable catalyst for Suzuki coupling reactions.

Selective catalytic reduction of NO x to N 2 by methanol as a reducing agent presents a prospective solution for the removal of NO x from the exhaust of methanol engines and the coal-fired power plant, but it confronts the problem of insufficient deNO x activity at low temperatures (<350 °C). Here, we discover a strategy for boosting the activity of low-temperature Methanol-SCR by the collaboration of zeolitic acid sites with single iron redox sites. The further pilot-scale bench test using the coated monolithic catalyst also exhibits a remarkable NO x conversion and a high stability at low temperature. The location of different Fe sites in FER zeolite is identified by X-ray absorption spectroscopy, Mössbauer spectroscopy, as well as 2D 1 H- 1 H DQ MAS NMR technology. While the dynamic evolution of [FeO] + as the critical redox site for NO oxidation is successfully captured by in situ Mössbauer spectroscopy, which unravels the mechanism for the generation of key intermediate HONO on [FeO] + sites contributing the low-temperature Methanol-SCR activity. These results indicate the great potential application of Fe-FER zeolite catalyst in industrial Methanol-SCR and provide an atomic-level comprehension of how the dual-active-sites contribute to low-temperature Methanol-SCR activity. Selective catalytic reduction of NOx to N₂ using methanol as the reductant (Methanol-SCR) offers a promising route for eliminating NOx emissions from methanol engines and coal-fired power plants, but its performance at low temperatures remains limited. Here, the authors identify a strategy to enhance low-temperature Methanol-SCR activity through the cooperation between zeolitic acid sites and single iron redox sites.

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.Oxynitride-supported Ni catalysts exhibit much higher activity than oxide-supported Ni catalysts for ammonia decomposition reaction. Ammonia is activated at nitrogen vacancy sites on the surface of oxynitride in close vicinity to the supported Ni nanoparticles rather than on the Ni surface, and therefore the catalytic performance is dominated by ease of nitrogen vacancy formation on the catalyst surface.

In 2012, we reported that C12A7 electride (C12A7: e−) significantly promotes the catalytic activity of Ru nanoparticles for ammonia synthesis through the electron donation from the C12A7: e− with a low work function (2.4 eV) to Ru [...]