Boosting N2O Decomposition by Fabricating the Cs-O-Co Structure over Co3O4 with Single-Layer Atoms of Cs

Enhanced Nitrous Oxide Decomposition on Zirconium-Supported Rhodium Catalysts by Iridium Augmentation

The effective elimination of N2O from automobile exhaust at low temperatures poses significant challenges. Compared to other materials, supported RhOx catalysts exhibit high N2O decomposition activities, even in the presence of O2, CO2, and H2O. Metal additives can enhance the low-temperature N2O decomposition activities over supported RhOx catalysts; however, the enhancement mechanism and active sites require further investigation. In this study, we demonstrate the significant enhancement of the low-temperature N2O decomposition activity of a monoclinic ZrO2-supported Rh catalyst [Rh(1)/ZrO2] with Ir addition in the presence of N2O + O2 + CO2 + H2O. The promotional effect of Ir and the active sites on N2O decomposition in Rh(1)-Ir(1)/ZrO2 (Rh = 1 wt % and Ir = 1 wt %) were investigated by kinetic studies and in situ spectroscopic methods, including X-ray absorption spectroscopy, ambient-pressure X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. These results indicate that both surface Rh and Ir species in Rh(1)-Ir(1)/ZrO2 were active sites for N2O catalytic decomposition at low temperatures, and Ir augmentation promoted the desorption of gaseous O2, which are regarded as key steps in N2O decomposition.

Insights into the Roles of Different Iron Species on Zeolites for N2O Selective Catalytic Reduction by CO

Iron zeolites are promising candidates for mitigating nitrous oxide (N2O), a potent greenhouse gas and contributor to stratospheric ozone destruction. However, the atomic-level mechanisms by which different iron species, including isolated sites, clusters, and particles, participate in N2O decomposition in the presence of CO still remain poorly understood, which hinders the application of the reaction in practical technology. Herein, through experiments and density functional theory (DFT) calculations, we identified that isolated iron sites were active for N2O activation to generate adsorbed O* species, which readily reacted with CO following the Eley-Rideal (E-R) mechanism. In contrast, Fe2O3 particles exhibited a different reaction pathway, directly reacting with CO to generate oxygen vacancies (Ov), which could efficiently dissociate N2O following the Mars-van Krevelen (MvK) mechanism. Moreover, the transformation of iron oxide clusters into undercoordinated FeOx species by CO was also revealed through various techniques, such as CO-temperature-programmed reduction (TPR), and ab initio molecular dynamics (AIMD) simulations. Our study provides deeper insights into the roles of different iron species in N2O-SCR by CO, and is anticipated to facilitate the understanding of multicomponent catalysis and the design of efficient iron-containing catalysts for practical applications.

Highly active Mn-VO-Co sites by cobalt doping on cryptomethane for enhanced catalytic decomposition of N2O

Direct catalytic decomposition has shown great promise in controlling the greenhouse gas N2O. Herein, we synthesize a series of cobalt-doped cryptomethane (OMS-2) catalysts for N2O catalytic decomposition by a mild one-step sol-gel method. The Co0.1-OMS-2 exhibits superior catalytic performance with 90% N2O conversion at 398 °C, which is attributed to the formation of the Mn-VO-Co structure served as active sites. The increased electron density on oxygen vacancies promotes the electron transfer between oxygen vacancies and N2O molecules, in turn facilitating the adsorption and activation of N2O. Moreover, Co doping reduces the formation energy of oxygen vacancies. However, excessive Co doping results in the decrease of highly active Mn-VO-Co sites and the formation of Co3O4, which makes Co0.3-OMS-2 exhibit poor catalytic activity. The DFT calculation illustrates that Langmuir-Hinshelwood is the primary reaction mechanism over Co0.1-OMS-2. This study broadens the materials applicable for the catalytic decomposition of N2O, offering an effective approach to modulate the electronic structure at oxygen vacancies.

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Enhancing low-temperature CO removal in complex flue gases: A study on La and Cu doped Co3O4 catalysts under real-world combustion environment

Designing CO oxidation catalysts for complex flue gases conditions is particularly challenging in fire scenarios. Traditional flue gas simulations use a few representative gases but often fail to adequately evaluate catalyst performance in real-world combustion conditions. In this study, we developed doping strategies using La and Cu to enhance the water resistance of Co3O4 catalysts. Catalyst 0.1La-Co3O4-CuO/CeO2 exhibits exceptional low-temperature catalytic activity, achieving 100% conversion at 130 °C. This enhancement is largely due to the introduction of La, which increases the active Co3+/Co2+ ratio and suppresses hydroxyl group formation on the Co3O4 surface. Cu doping also changes the Co3O4 lattice structure, forming Cu+ as active sites and enhancing the activity at low temperatures. For the first time, steady-state tube furnace and fixed bed were employed to evaluate the catalytic performance of CO in actual combustion atmosphere. Catalyst 0.1La-Co3O4-CuO/CeO2 maintains excellent catalytic efficiency (T100 = 120 °C) under well-ventilated conditions. However, its activity significantly decreases in poorly ventilated environments, due to the competitive adsorption of small molecules at active sites, such as acetone, commonly found in smoke. This study provides valuable insights for designing water-resistant, low-temperature, non-noble metal catalysts and offers a methodology for evaluating CO catalytic activity in real-world environments.