Machine learning-based QSAR and LB-PaCS-MD guided design of SARS-CoV-2 main protease inhibitors.

The global outbreak of the COVID-19 pandemic caused by the SARS-CoV-2 virus had led to profound respiratory health implications. This study focused on designing organoselenium-based inhibitors targeting the SARS-CoV-2 main protease (Mpro). The ligand-binding pathway sampling method based on parallel cascade selection molecular dynamics (LB-PaCS-MD) simulations was employed to elucidate plausible paths and conformations of ebselen, a synthetic organoselenium drug, within the Mpro catalytic site. Ebselen effectively engaged the active site, adopting proximity to H41 and interacting through the benzoisoselenazole ring in a π-π T-shaped arrangement, with an additional π-sulfur interaction with C145. In addition, the ligand-based drug design using the QSAR with GFA-MLR, RF, and ANN models were employed for biological activity prediction. The QSAR-ANN model showed robust statistical performance, with an r2training exceeding 0.98 and an RMSEtest of 0.21, indicating its suitability for predicting biological activities. Integration the ANN model with the LB-PaCS-MD insights enabled the rational design of novel compounds anchored in the ebselen core structure, identifying promising candidates with favorable predicted IC50 values. The designed compounds exhibited suitable drug-like characteristics and adopted an active conformation similar to ebselen, inhibiting Mpro function. These findings represent a synergistic approach merging ligand and structure-based drug design; with the potential to guide experimental synthesis and enzyme assay testing.

Spheroidization: The Impact of Precursor Morphology on Solid-State Lithiation Process for High-Quality Ultrahigh-Nickel Oxide Cathodes.

Layered oxides with ultrahigh nickel content are considered promising high energy cathode materials. However, their cycle stability is constrained by a series of heterogeneous structural transformations during the complex solid-state lithiation process. By in-depth investigation into the solid-state lithiation process of LiNi0.92Co0.04Mn0.04O2, it is found that the protruded parts on the surface of precursor particles tend to be surrounded by locally excessive LiOH, which promotes the formation of a rigid and dense  shell during the early stage of lithiation process. The shell will hinder the diffusion of lithium and topotactic lithiation within the particles, culminating in spatially heterogeneous intermediates that can impair the electrochemical properties of the cathode material. The spheroidization of the precursor can enhance uniformity in structural evolution during solid-phase lithiation. Ultrahigh nickel cathodes derived from spherical precursors demonstrate high initial discharge specific capacity (234.2 mAh g-1, in the range of 2.7-4.3V) and capacity retention (89.3% after 200 cycles), significantly superior to the non-spherical samples. This study not only sheds light on the intricate relationship between precursor shape and structural transformation but also introduces a novel strategy for enhancing cathode performance through precursor spheroidization.

A 3D Cross-Linked Metal-Organic Framework (MOF)-Derived Polymer Electrolyte for Dendrite-Free Solid-State Lithium-Ion Batteries.

Lithium metal batteries (LMBs) with high energy density have received widespread attention; however, there are usually issues with lithium dendrite growth and safety. Therefore, there is a demand for solid electrolytes with high mechanical strength, room-temperature ionic conductivity, and good interface performance. Herein, a 3D cross-linked metal-organic framework (MOF)-derived polymer solid electrolyte exhibits good mechanical and ionic conductive properties simultaneously, in which the MOF with optimized pore size and strong imidazole cation sites can restrict the migration of anions, resulting in a uniform Li+ flux and a high lithium-ion transference number (0.54). Moreover, the MOF-derived polymer solid electrolytes with the 3D cross-linked network can promote the rapid movement of Li+ and inhibit the growth of lithium dendrites. Lithium symmetric batteries assembled with the 3D MOF-derived polymer solid electrolytes are subjected to lithium plating/stripping and cycled over 2000 h at a current density of 0.1 mA cm-2 and over 800 h at a current density of 0.2 mA cm-2 . The Li/P-PETEA-MOF/LiFePO4 batteries exhibit excellent long-cycle stability and cycle reversibility.

An Asymmetric Cross-Linked Ionic Copolymer Hybrid Solid Electrolyte with Super Stretchability for Lithium-Ion Batteries.

Composite solid electrolytes are recommended to be the most promissing strategy for solid-state batteries because they combine the advantages of inorganic ceramics and polymers. However, the huge interfacial resistance between the inorganic ceramic and polymer results in low ionic conductivity, which is still the major impediment that limits their applications. Herein, a novel highly elastic and weakly coordinated ionic copolymer hybrid electrolyte with asymmetric structure based on surface-modified Li1.5 Al0.5 Ge1.5 (PO4 )3 by "in situ" polymerization is proposed to improve ionic conductivity and mechanical properties simultaneously. The all-solid hybrids electrolytes exhibit room-temperature ionic conductivity up to 2.61 × 10-4 S cm-1 and lithium-ion transference number of 0.41. The hybrids electrolytes can be repeatedly stretching-releasing-stretching, showing a super stretchability with the elongation at break up to 496%. The Li symmetrical cells assembled with the hybrid electrolytes can continuously operate for 800 h at 0.1 mA cm-2 without discernable dendrites, indicating good interfacial compatibility between the hybrid electrolytes and lithium electrodes. The Li|LiFePO4 batteries assembled with the hybrid electrolytes deliver an initial discharge specific capacity of 165.5 mAh g-1 with an initial coulombic efficiency of 94.8% and 154 mAh g-1 after 100 cycles at 0.1 C, and maintain 95.4% capacity retention after 100 cycles at 0.5 C.

Rational Design of a Low-Data Regime of Pyrrole Antioxidants for Radical Scavenging Activities Using Quantum Chemical Descriptors and QSAR with the GA-MLR and ANN Concepts.

A series of pyrrole derivatives and their antioxidant scavenging activities toward the superoxide anion (O2•-), hydroxyl radical (•OH), and 1,1-diphenyl-2-picryl-hydrazyl (DPPH•) served as the training data sets of a quantitative structure-activity relationship (QSAR) study. The steric and electronic descriptors obtained from quantum chemical calculations were related to the three O2•-, •OH, and DPPH• scavenging activities using the genetic algorithm combined with multiple linear regression (GA-MLR) and artificial neural networks (ANNs). The GA-MLR models resulted in good statistical values; the coefficient of determination (R2) of the training set was greater than 0.8, and the root mean square error (RMSE) of the test set was in the range of 0.3 to 0.6. The main molecular descriptors that play an important role in the three types of antioxidant activities are the bond length, HOMO energy, polarizability, and AlogP. In the QSAR-ANN models, a good R2 value above 0.9 was obtained, and the RMSE of the test set falls in a similar range to that of the GA-MLR models. Therefore, both the QSAR GA-MLR and QSAR-ANN models were used to predict the newly designed pyrrole derivatives, which were developed based on their starting reagents in the synthetic process.

Quantitative Structure-Electrochemistry Relationship (QSER) Studies on Metal-Amino-Porphyrins for the Rational Design of CO2 Reduction Catalysts.

The quantitative structure-electrochemistry relationship (QSER) method was applied to a series of transition-metal-coordinated porphyrins to relate their structural properties to their electrochemical CO2 reduction activity. Since the reactions mainly occur within the core of the metalloporphyrin catalysts, the cluster model was used to calculate their structural and electronic properties using density functional theory with the M06L exchange-correlation functional. Three dependent variables were employed in this work: the Gibbs free energies of H*, C*OOH, and O*CHO. QSER, with the genetic algorithm combined with multiple linear regression (GA-MLR), was used to manipulate the mathematical models of all three Gibbs free energies. The obtained statistical values resulted in a good predictive ability (R2 value) greater than 0.945. Based on our QSER models, both the electronic properties (charges of the metal and porphyrin) and the structural properties (bond lengths between the metal center and the nitrogen atoms of the porphyrin) play a significant role in the three Gibbs free energies. This finding was further applied to estimate the CO2 reduction activities of the metal-monoamino-porphyrins, which will prove beneficial in further experimental developments.

Highly Selective Catalytic Oxi-upcycling of Polyethylene to Aliphatic Dicarboxylic Acid under a Mild Hydrogen-Free Process.

A low-temperature hydrogen-free process for upcycling polyethylene (PE) plastics into aliphatic dicarboxylic acid is developed using a heterogeneous catalyst Ru/TiO2 . The low-density PE (LDPE) conversion can reach 95 % in 24 h under a pressure of 1.5 MPa air at 160 °C with 85 % of the liquid product yield, which mainly is low molecular weight aliphatic dicarboxylic acid. Excellent performances can be also achieved for different PE feedstocks. This catalytic oxi-upcycling process paving a new way of upcycling polyethylene waste.

SO2-Tolerant Catalytic Reduction of NOx via Tailoring Electron Transfer between Surface Iron Sulfate and Subsurface Ceria.

Currently, SO2-induced catalyst deactivation from the sulfation of active sites turns to be an intractable issue for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures. Herein, SO2-tolerant NOx reduction has been originally demonstrated via tailoring the electron transfer between surface iron sulfate and subsurface ceria. Engineered from the atomic layer deposition followed by the pre-sulfation method, the structure of surface iron sulfate and subsurface ceria was successfully constructed on CeO2/TiO2 catalysts, which delivered improved SO2 resistance for NOx reduction at 250 °C. It was demonstrated that the surface iron sulfate inhibited the sulfation of subsurface Ce species, while the electron transfer from the surface Fe species to the subsurface Ce species was well retained. Such an innovative structure of surface iron sulfate and subsurface ceria notably improved the reactivity of NHx species, thus endowing the catalysts with a high NOx reaction efficiency in the presence of SO2. This work unraveled the specific structure effect of surface iron sulfate and subsurface ceria on SO2-toleant NOx reduction and supplied a new point to design SO2-tolerant catalysts by modulating the unique electron transfer between surface sulfate species and subsurface oxides.

Self-Defense Effects of Ti-Modified Attapulgite for Alkali-Resistant NOx Catalytic Reduction.

Nowadays, the serious deactivation of deNOx catalysts caused by alkali metal poisoning was still a huge bottleneck in the practical application of selective catalytic reduction of NOx with NH3. Herein, alkali-resistant NOx catalytic reduction over metal oxide catalysts using Ti-modified attapulgite (ATP) as supports has been originally demonstrated. The self-defense effects of Ti-modified ATP for alkali-resistant NOx catalytic reduction have been clarified. Ti-modified ATP with self-defense ability was obtained by removing alkaline metal cation impurities in the natural ATP materials without destroying its initial layered-chain structure through the ion-exchange procedure, accompanied with an obvious enrichment of Brønsted acid and Lewis acid sites. The self-defense effects embodied that both ion-exchanged Ti octahedral centers and abundant Si-OH sites in the Ti-ion-exchange-modified ATP could effectively anchor alkali metals via coordinate bonding or ion-exchange process, which induced alkali metals to be immobilized by the Ti-ion-exchange-modified ATP carrier rather than impair active species. Under this special protection of self-defense effects, Ti-ion-exchange-modified ATP supported catalysts still retained plentiful acidic sites and superior redox ability even after alkali metal poisoning, giving rise to the maintenance of sufficient NHx and NOx adsorption and the subsequent efficient reaction, which in turn resulted in high NOx catalytic reduction capacity of the catalyst. The strategy provided new inspiration for the development of novel and efficient selective catalytic reduction of NOx with NH3 (NH3-SCR) catalysts with high alkali resistance.

Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects.

Selective catalytic reduction with NH3 (NH3-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NOx) from coal-fired industries, diesel engines, etc. Although V2O5-WO3(MoO3)/TiO2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO2/alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH3-SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VOx, MnOx, CeO2, and Fe2O3 to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc. exchanged zeolite catalysts; monolith catalysts including extruded, washcoated, and metal-mesh/foam-based monolith catalysts. The challenges and opportunities for each type of catalysts are proposed while the effective strategies are summarized for enhancing the acidity/redox circle and poison-resistance through modification, creating novel nanostructures, exposing specific crystalline planes, constructing protective/sacrificial sites, etc. Some suggestions are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and practical requirements to realize their commercial applications in the near future.

Selective Capacitive Removal of Pb2+ from Wastewater over Redox-Active Electrodes.

Water pollution has become an environmental hazard. Diverse metal cations exist in wastewater; lead is the most common heavy metal pollutant among them. Selective removal of highly toxic and ultradiluted lead ions from wastewater is a major challenge for water purification. Here, selective capacitive removal (SCR) of lead ions from wastewater over redox-active molybdenum dioxide/carbon (MoO2/C) electrodes was developed by an environment-friendly asymmetric capacitive deionization (CDI) method. The MoO2/C spheres act as cathodes of an asymmetric CDI device and effectively reduce the concentration of Pb2+ from 50 ppm to <0.21 ppb. Moreover, the SCR efficiency of lead ions over redox-active MoO2/C electrodes is >99% in mixtures of 100 ppm Pb(NO3)2 and 100 ppm NaCl solutions. In addition, the electrodes exhibit high regeneration performance in mixtures of NaCl and Pb(NO3)2 and high SCR efficiency for lead ions from mixtures of heavy metal ions. The tetrahedral structure of the [MoO4] lattice is shown to be more favorable for the intercalation of lead ions. In situ Raman spectroscopy further shows that the transition of the crystal interface between [MoO6] and [MoO4] cluster lattice could be electrochemically controlled during SCR. Therefore, this study provides a new direction for the SCR of lead ions from wastewater.

Trace-Fe-Enhanced Capacitive Deionization of Saline Water by Boosting Electron Transfer of Electro-Adsorption Sites.

Capacitive deionization (CDI) is a promising water purification technology. However, the current ion adsorption capacity of CDI electrode materials is still an issue, which cannot meet the rapid demand of clean water from saline water. Herein, trace-Fe-enhanced removal of ions from saline water via CDI is presented. The ion adsorption capacity of CDI electrodes is up to 36.25 mg g-1 in a 500 mg L-1 NaCl media at 1.2 V together with stable regeneration property. In situ Raman and ex situ XPS measurements unravel the removal mechanism of ions from saline water, and the reinforced adsorption of ions is due to the introduction of trace Fe boosting electron transfer of electro-adsorption sites during the CDI process. This work presents a promising solution to highly efficient capacitive deionization for saline water.

Boosting Toluene Combustion by Engineering Co-O Strength in Cobalt Oxide Catalysts.

Exploring active and low-cost transition metal oxides (TMOs) based catalysts for volatile organic compounds (VOCs) abatement is vital for air pollution control technologies. Since 18 oxygen atoms are required for the complete mineralization of a toluene molecule, the participation of a large amount of active oxygen is a key requirement for the catalytic oxidation of toluene. Here, toluene degradation was improved by weakening the Co-O bond strength on the surface of cobalt oxide, so as to increase the amount of active oxygen species, while maintaining the high stability of the catalyst for toluene combustion. The bond strength of Co-O and the amount of surface active O2 was regulated by tuning the pyrolysis temperature. The catalyst's redox ability and surface oxygen species activity are improved due to the weakening of the Co-O bond strength. It has been demonstrated that active oxygen plays a crucial role in boosting toluene combustion by engineering Co-O strength in cobalt oxide catalysts. This work provides a new understanding of the exploration and development of high-performance TMO catalysts for VOCs abatement.

Poisoning-Resistant NOx Reduction in the Presence of Alkaline and Heavy Metals over H-SAPO-34-Supported Ce-Promoted Cu-Based Catalysts.

Selective catalytic reduction (SCR) of NOx using NH3 in the presence of alkaline and heavy metals is still an issue in the application of a stationary source. Reported here is the rational design of a novel H-SAPO-34-supported ceria-promoted copper-based catalyst (CuCe/H-SAPO-34) that demonstrates exceptional resistance against alkali (K), alkaline earth (Ca), and heavy metal (Pb) poisoning during SCR of NOx. The H-SAPO-34 support contained numerous acid sites that allowed Cu-based catalysts to maintain their catalytic activity while also resisting poisoning by K and Ca. Decorating the catalyst with CeO2 promoted the low-temperature deNOx activity by accelerating the redox cycle with Cu species and assisted the H-SAPO-34 in capturing Ca and Pb. H-SAPO-34-supported ceria-promoted copper oxide catalysts prevented the irreversible combination of K, Ca, or Pb with the active centers, providing the catalyst with excellent poisoning resistance. This work provides a strategy for the development of high-performance, poisoning-resistant catalysts for NH3-SCR of NOx in the presence of alkaline and heavy metals.

Self-Protected CeO2-SnO2@SO42-/TiO2 Catalysts with Extraordinary Resistance to Alkali and Heavy Metals for NOx Reduction.

Reducing the poisoning effect of alkali and heavy metals over ammonia selective catalytic reduction (NH3-SCR) catalysts is still an intractable issue, as the presence of K and Pb in fly ash greatly hampers their catalytic activity by impairing the acidity and affecting the redox properties of the catalysts, leading to the reduction in the lifetime of SCR catalysts. To address this issue, we propose a novel self-protected antipoisoning mechanism by designing SO42-/TiO2 superacid supported CeO2-SnO2 catalysts. Owing to the synergistic effect between CeO2 and SnO2 and the strong acidity originating from the SO42-/TiO2 superacid, the catalysts show superior catalytic activity over a wide temperature range (240-510 °C). Moreover, when K or/and Pb are deposited on SO42-/TiO2 catalysts, the bond effect between SO42- and Ti-O would be broken so that the sulfate in the bulk of SO42-/TiO2 superacid support would be induced to migrate to the surface to bond with K and Pb, thus prohibiting poisons from attacking the Ce-Sn active sites, and significantly boosting the resistance. Hopefully, this novel self-protection mechanism derived from the migration of sulfate in the SO42-/TiO2 superacid to resist alkali and heavy metals provides a new avenue for designing novel catalysts with outstanding resistance to alkali and heavy metals.

Alkali-Resistant NOx Reduction over SCR Catalysts via Boosting NH3 Adsorption Rates by In Situ Constructing the Sacrificed Sites.

Currently, improving the alkali resistance of vanadium-based catalysts still remains as an intractable issue for the selective catalytic reduction of NOx with NH3 (NH3-SCR). It is generally believed that the decrease in adsorbed NHx species deriving from the declined acidic sites is the chief culprit for the deactivation of alkali-poisoned catalysts. Herein, alkali-resistant NOx reduction over SCR catalysts via boosting NH3 adsorption rates was originally demonstrated by in situ constructing the sacrificed sites. It is interesting that the adsorbed NHx species largely decrease while the NH3 adsorption rate is well kept over the V2O5/CeO2 catalyst by in situ constructing the sacrificed sites. The SCR activity could be maintained after alkali poisoning because in situ constructed SO42- groups would prefer to be combined with K+ so that the specific V═O species can endow K-poisoned V2O5/CeO2 with high adsorption rate of NH3 and high reactivity of NHx species. This work provides a new viewpoint that NH3 adsorption rate plays more decisive roles in the performance of alkali-poisoned catalysts than the amount of NH3 adsorption and enlightens an alternative strategy to improve the alkali-resistance of catalysts, which is significant to both the academic and industrial fields.

SO2-Tolerant NOx Reduction by Marvelously Suppressing SO2 Adsorption over FeδCe1-δVO4 Catalysts.

SO2-tolerant selective catalytic reduction (SCR) of NOx at low temperature is still challenging. Traditional metal oxide catalysts are prone to be sulfated and the as-formed sulfates are difficult to decompose. In this study, we discovered that SO2 adsorption could be largely restrained over FeδCe1-δVO4 catalysts, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO2 tolerance at an extremely low temperature of 240 °C. The increasing oxygen vacancies, enhanced redox properties, and improved acidity contributed to the SCR activity of the FeδCe1-δVO4 catalyst. The reaction pathway changed from the reaction between bidentate nitrate and the NH3 species over CeVO4 catalysts via the Langmuir-Hinshelwood mechanism to that between gaseous NOx and the NH4+/NH3 species over FeδCe1-δVO4 catalysts via the Eley-Rideal mechanism. The effective suppression of SO2 adsorption allowed FeδCe1-δVO4 catalysts to maintain the Eley-Rideal pathways on account of the reduced formation of sulfate species. This work demonstrated an effective route to improve SO2 tolerance via modulating SO2 adsorption on Ce-based vanadate catalysts, which presented a new point for the development of high-performance SO2-tolerant SCR catalysts.

Alkali and Phosphorus Resistant Zeolite-like Catalysts for NOx Reduction by NH3.

At present, the deactivation of selective catalytic reduction (SCR) catalysts caused by the coexistence of alkali metal and phosphorus (P) remains an urgent problem and lacks corresponding strategies against catalyst poisoning. Herein, a novel zeolite-like Ce-Si5Al2Ox catalyst derived from an ultrasmall nanozeolite EMT precursor was synthesized without organic templates at ambient temperature. This catalyst was able to maintain above 95% NOx conversion in the 270-540 °C temperature range. Moreover, 1 wt % potassium (K) and 5 wt % P loading had no influence on the SCR performance of the Ce-Si5Al2Ox catalyst at 300-480 °C. It was demonstrated that cerium (Ce) was highly dispersed in the amorphous aluminum (Al) silicate derived from EMT zeolites and expressed high catalytic performance. Besides, a large number of acid sites were reserved to absorb ammonia allowing effective participation in the SCR reaction and capturing alkali metals, thus improving the SCR performance and K resistance. Additionally, the strong interaction between Ce and aluminosilicate decreased cerium phosphate production, preventing deactivation of the catalysts. Thus, this novel low-cost zeolite-like Ce-Si5Al2Ox catalyst with a highly active ion-exchanged metal phase and abundant surface acid sites paves a way for designing new efficient and poisoning-resistant SCR catalysts for practical applications.

Exceptional Mechanical Properties of Phase-Separation-Free Mo3Se3--Chain-Reinforced Hydrogel Prepared by Polymer Wrapping Process.

As Mo3Se3- chain nanowires have dimensions comparable to those of natural hydrogel chains (molecular-level diameters of ∼0.6 nm and lengths of several micrometers) and excellent mechanical strength and flexibility, they have large potential to reinforce hydrogels and improve their mechanical properties. When a Mo3Se3--chain-nanowire-gelatin composite hydrogel is prepared simply by mixing Mo3Se3- nanowires with gelatin, phase separation of the Mo3Se3- nanowires from the gelatin matrix occurs in the micronetwork, providing only small improvements in their mechanical properties. In contrast, when the surface of the Mo3Se3- nanowire is wrapped with the gelatin polymer, the chemical compatibility of the Mo3Se3- nanowire with the gelatin matrix is significantly improved, which enables the fabrication of a phase-separation-free Mo3Se3--reinforced gelatin hydrogel. The composite gelatin hydrogel exhibits significantly improved mechanical properties, including a tensile strength of 27.6 kPa, fracture toughness of 26.9 kJ/m3, and elastic modulus of 54.8 kPa, which are 367%, 868%, and 378% higher than those of the pure gelatin hydrogel, respectively. Furthermore, the amount of Mo3Se3- nanowires added in the composite hydrogel is as low as 0.01 wt %. The improvements in the mechanical properties are significantly larger than those for other reported composite hydrogels reinforced with one-dimensional materials.

Fe2O3-CeO2@Al2O3 Nanoarrays on Al-Mesh as SO2-Tolerant Monolith Catalysts for NO x Reduction by NH3.

Currently, selective catalytic reduction of NO x with NH3 in the presence of SO2 is still challenging at low temperatures (<300 °C). In this study, enhanced NO x reduction was achieved over a SO2-tolerant Fe-based monolith catalyst, which was originally developed through in situ construction of Al2O3 nanoarrays (na-Al2O3) on the monolithic Al-mesh by a steam oxidation method followed by anchoring Fe2O3 and CeO2 onto the na-Al2O3@Al-mesh composite by an impregnation method. The optimum catalyst delivered more than 90% NO conversion and N2 selectivity above 98% within 250-430 °C as well as excellent SO2 tolerance at 270 °C. The strong interaction between Fe2O3 and CeO2 enabled favorable electron transfers from Fe2O3 to CeO2 while generating more oxygen vacancies and active oxygen species, consequently accelerating the redox cycle. The improved reactivity of NH4+ with nitrates following the Langmuir-Hinshelwood mechanism and active NH2 species that directly reacted with gaseous NO following the Eley-Rideal mechanism enhanced the NO x reduction efficiency at low temperatures. The preferential sulfation of CeO2 alleviated the sulfation of Fe2O3 while maintaining the high reactivities of NH4+ and NH2 species. Especially, the SCR reaction following the Eley-Rideal mechanism largely improved the SO2 tolerance because NO does not need to compete with sulfates to adsorb on the catalyst surface as nitrates or nitrites. This work paves a way for the development of high-performance SO2-tolerant SCR monolith catalysts.