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•The ball-flowerlike structure of CoMnOx-BF catalyst could remarkably enhance its low-temperature SCR activity.•More ad-NH3 and ad-NOx species with higher reactivity are available on ...the surface of CoMnOx-BF catalyst.•The redox cycle “Mn4+ + Co2+ ↔ Mn3+ + Co3+” greatly promotes the low-temperature SCR reaction over CoMnOx-BF catalyst.
A novel ball-flowerlike catalyst (CoMnOx-BF) was developed by hydrothermal method for the selective catalytic reduction (SCR) of NOx by NH3. Besides, a counterpart sample (CoMnOx) was prepared by coprecipitation way for comparison. The activity test results demonstrated that CoMnOx-BF catalyst exhibited admirable SCR performance and N2 selectivity in a broad temperature range of 150–350 °C, along with an excellent resistance to SO2 and high durability. Based on characterization experiments, it could be found that the superior surface area resulted from suppressed crystallization, the enrichment of surface labile oxygen and Mn4+, the stronger surface acidity and redox ability were all beneficial to the NH3-SCR performance of CoMnOx-BF catalyst. Additionally, the enhanced NO oxidation and more activated ad-reactants on catalyst surface could also conduce to the outstanding SCR activity of CoMnOx-BF at low temperature.
Excessive greenhouse gas emissions have led to a series of environmental problems, such as the increasing greenhouse effect, rising sea levels, and melting glaciers at the poles, threatening the ...global environment for human existence. In view of this, the development of CO2 capture technologies with commercialization potential is imperative, as CO2 is the primary contributor to greenhouse gases. In recent years, chemical absorption techniques founded on sterically hindered amines, such as 2-amino-2-methyl-1-propanol (AMP), have garnered escalating interest owing to their benefits of large absorption capacity and diminished energy consumption for regeneration as compared to traditional amine-based methods. In this review, the steric hindrance effect of a sterically hindered amine and its reaction mechanism with CO2 are reviewed. Subsequently, sterically hindered amine absorbents are classified into four kinds, single amine absorbents, blended amine absorbents, biphasic amine absorbents, and nonaqueous amine absorbents, and recent advancements in investigating the kinetic and thermodynamic characteristics of carbon dioxide sequestration through the utilization of sterically hindered amine sorbents are comprehensively evaluated. Technical-economic analysis and life cycle assessment of the CO2 capture processes based on sterically hindered amine absorbents have been comprehensively reviewed. Furthermore, future work for CO2 capture technologies based on sterically hindered amines is suggested.
Energy shortage and global warming caused by the extensive use of fossil fuels are urgent problems to be solved at present. Photoreduction of CO2 is considered to be a feasible solution. The ternary ...composite catalyst g‐C3N4/Ti3C2/MoSe2 was synthesized by hydrothermal method, and its physical and chemical properties were studied by an array of characterization and tests. In addition, the photocatalytic performance of this series of catalysts under full spectrum irradiation was also tested. It is found that the CTM‐5 sample has the best photocatalytic activity, and the yields of CO and CH4 are 29.87 and 17.94 μmol g−1 h−1, respectively. This can be ascribed to the favorable optical absorption performance of the composite catalyst in the full spectrum and the establishment of S‐scheme charge transfer channel. The formation of heterojunctions can effectively promote charge transfer. The addition of Ti3C2 materials provides plentiful active sites for CO2 reaction, and its superior electrical conductivity is also favorable for the migration of photogenerated electrons.
In this study, a remarkable offset deactivation effect of K and P on MnEuOx SCR catalyst has been found. Experimental results showed that the NO conversion over K−P poisoned catalyst was close to 80 ...% at 250 °C. Several characterization techniques containing NH3‐TPD, XPS, H2‐TPR, XRD and in situ DRIFT were used to reveal the mechanism of the offset effect. The characterization of NH3‐TPD and H2‐TPR suggested that the introduction of P on MnEuOx‐K could improve its surface acidity and redox ability. Moreover, the content of chemisorbed oxygen and Mn4+ were markedly restored under the situation that the toxic elements were coexistent on catalyst surface. The strong interaction between K and P might be the major reason for the offset deactivation effect. More specifically, PO3− species were preferentially bonded with the surface potassium species and released MnO2 active sites poisoned by K. Therefore, the highly active MnO2 sites might be protected and the catalytic activity could be restored.
PO3− species were preferentially bonded with the surface potassium species and released MnO2 active sites poisoned by K. The highly active MnO2 sites might be protected and the catalytic activity could be restored.
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Photocatalytic reduction of CO2 to high-energy products is an effective way to utilize solar energy and mitigate the greenhouse effect. In this paper, a series of ...CQDs/Bi12O17Cl2/NiAl-LDH (C/BOC/LDH) photocatalysts were prepared via a one-pot hydrothermal method, demonstrated excellent photocatalytic CO2 reduction performance. In the case of only water without any photosensitizer and sacrificial agent, the CO production rate on C/0.3BOC/LDH reached 16.4 μmol·g-1h−1, which is 6.7 times higher than that of the original LDH. The construction of Z-scheme heterojunctions inhibited the recombination of electrons with holes. The unique up-conversion PL behavior of CQDs benefitted the absorption of energy in the NIR by the photocatalyst. This study provides meaningful assistance for the design and construction of a ternary photocatalytic system with Z-scheme heterojunction and carbon-based co-catalyst.
Photocatalytic CO2 reduction (PCO2RR) is regarded as a promising means to mitigate the effects of climate change and current energy shortage. However, photocatalysis is not very effective because of ...the rapid recombination of photogenerated electron–hole pairs. S-scheme heterojunctions can effectively separate photogenerated carriers and significantly improve the redox ability of photocatalysts. In recent years, S-scheme heterojunction photocatalysts have become a popular topic of research because of their superior photocatalytic performance. This review examines the recent research advancements in S-scheme heterojunction photocatalysts. First, the principle of PCO2RR is briefly introduced. Various types of heterojunctions are introduced, the charge transfer mechanisms and characterization methods of S-scheme heterojunctions are described, and the applications of metal oxides, metal sulfides, and other S-scheme photocatalysts in CO2 reduction are discussed and reviewed, respectively. In conclusion, the limitations and prospective directions of S-scheme heterojunction photocatalysts in CO2 photoreduction are discussed to provide direction for the design of high-performance S-scheme heterojunction photocatalysts.
Photocatalytic reduction of CO2 into hydrocarbon fuels, utilizing inexhaustible solar energy to simulate natural photosynthesis, is a promising approach to simultaneously alleviate environmental ...issues and energy crises. Among the developed photocatalysts, bismuth (Bi)-based materials have been extensively applied for photocatalytic CO2 reduction due to their unique electronic configuration and excellent physicochemical properties. Various approaches have been investigated to enhance the photocatalytic performance of Bi-based photocatalysts for CO2 reduction, among which constructing direct or indirect Z-scheme by coupling Bi-based materials with matching semiconductors is an effective method. In this review, the latest major advancements in the design of high-efficient Bi-based Z-scheme photocatalysts for photocatalytic CO2 reduction are summarized, including structural engineering strategies for direct Z-scheme and several patterns of indirect Z-scheme construction. Moreover, the proposed S-scheme structure based on the Z-scheme structure is also briefly discussed. Finally, the current challenges and prospects of the future development of the Bi-based Z-scheme structure for CO2 photoreduction are also presented and discussed.
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•The progress on photocatalytic CO2 reduction over Bi-based Z-scheme photocatalysts are summarized.•The relationship between Bi-based Z-scheme structure and the photocatalytic CO2 reduction activity was investigated.•The future development of the Bi-based Z-scheme structure for CO2 photoreduction is discussed.
Converting CO
into value-added products by photocatalysis, electrocatalysis, and photoelectrocatalysis is a promising method to alleviate the global environmental problems and energy crisis. Among ...the semiconductor materials applied in CO
catalytic reduction, Cu
O has the advantages of abundant reserves, low price and environmental friendliness. Moreover, Cu
O has unique adsorption and activation properties for CO
, which is conducive to the generation of C
products through CC coupling. This review introduces the basic principles of CO
reduction and summarizes the pathways for the generation of C
, C
, and C
products. The factors affecting CO
reduction performance are further discussed from the perspective of the reaction environment, medium, and novel reactor design. Then, the properties of Cu
O-based catalysts in CO
reduction are summarized and several optimization strategies to enhance their stability and redox capacity are discussed. Subsequently, the application of Cu
O-based catalysts in photocatalytic, electrocatalytic, and photoelectrocatalytic CO
reduction is described. Finally, the opportunities, challenges and several research directions of Cu
O-based catalysts in the field of CO
catalytic reduction are presented, which is guidance for its wide application in the energy and environmental fields is provided.
Heavy metals (such as Zn and Pb) have a deactivation effect on the catalyst for selective catalytic reduction of NO with NH3. In this study, it was found that the modification of Mn/TiO2 catalyst by ...Nb could greatly enhance its Zn resistance. From the characterization results of BET, XRD, H2-TPR, NH3-TPD, it may be concluded that the introduction of Nb into Mn/TiO2 catalyst would lead to its lower crystallinity, more acid sites and higher concentrations of Mn4+ and surface chemisorbed oxygen. The results of in situ DRIFT study reveal that the NH3-SCR reactions over Mn/TiO2 and Mn-Nb/TiO2 all obey both the Langmuir-Hinshelwood mechanism and the Eley–Rideal mechanism, and the doping of Nb on Mn/TiO2 catalyst could promote the adsorption of NH3 and NOx species on it. All these features make a contribution to the high SCR activity and good Zn resistance of Mn-Nb/TiO2 catalyst.
•Mn-Nb/TiO2 catalyst has higher SCR activity and better Zn resistance than Mn/TiO2 catalyst.•The modification of Mn/TiO2 catalyst by Nb could promote the adsorption of NH3 species and NOx species.•The NH3-SCR reactions over Mn/TiO2 and Mn-Nb/TiO2 are all controlled by the L-H mechanism and the E–R mechanism.
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