Biotemplate Fabrication of Hollow Tubular CexSr1-xTiO3 with Regulable Surface Acidity and Oxygen Mobility for Efficient Destruction of Chlorobenzene: Intrinsic Synergy Effect and Reaction Mechanism

Synergistic catalytic removal of NOx and chlorobenzene by a combination punch of Lewis and Bronsted acid and redox sites

Multi-pollutant control of nitrogen oxides (NOx) and chlorinated aromatics in industrial flue by synergistic catalysis is still a huge challenge. Tailoring well-defined interfacial structures of multi-component heterogeneous catalysts has become an effective strategy for facilitating reactions involving multiple reactants. Here, a coupling of copper and tin oxide with particle-particle heterostructure supported on H-ZSM5 is designed to achieve a high-performance catalyst for NOx and chlorobenzene synergistic elimination. Experimental and theoretical calculation (DFT) studies show that the particle-particle coupling Janus heterostructure induced Sn-O-Cu interfaces. The strong electronic interaction improves the interfacial charge redistribution and mediates the activated interfacial oxygen, supporting redox (R) sites for the redox reaction cycle. Together with the abundant intrinsic Lewis (L) acid sites from CuOx and Brønsted (B) acid sites from the H-ZSM-5 interface, a combination punch of ideal L-B-R sites was constructed for the synergistic catalysis of NOx reduction and chlorobenzene oxidation. The designed Sn-Cu/H-ZSM5 catalyst exhibits significant low-temperature synergistic catalytic activity, a wide temperature window, robust long-term stability, and excellent water resistance, which outperforms Sn/H-ZSM5 and Cu/H-ZSM5. Moreover, in situ infrared spectra of serial transient reactions evidenced that the NOx reduction reaction promotes chlorobenzene oxidation. This novel strategy of regulating the overall L acid, B acid, and redox properties to fabricate balanced L-B-R sites via interfacial engineering provides a distinct strategy for facilitating the synergistic abatement of NOx and chlorinated aromatics.

Insight into the reaction mechanism of NH3-SCR and chlorobenzene oxidation over Mn-based spinel catalysts

To evaluate potential of Mn-based spinel catalysts for multi-pollutant removal applications, a series of Mn-based spinel catalysts were developed and tested for NH3 selective catalytic reduction (NH3-SCR) reaction and chlorobenzene catalytic oxidation. It was found that the CrMn2O4 spinel catalysts showed the best NH3-SCR activity and chlorobenzene catalytic removal activity among these Mn-based spinel catalysts. A NO removal efficiency above 90 % was achieved in the range of 163-283 °C with an apparent activation energy of 32.26 kJ/mol, whereas 90 % of chlorobenzene removal was achieved at nearly 300 °C with an apparent activation energy of 61.41 kJ/mol. CrMn2O4 exhibits the good performance for simultaneous removal of NO and chlorobenzene in the temperature range of 305-315 °C. Stability tests indicates that 6 vol% water inhibits the NH3-SCR reaction, but promoted the chlorobenzene oxidation and CO2 yield. Its porous and fluffy structure provides a large specific surface area of 29.32 m2/g and facilitates the adsorption of reactants. The DFT calculations were used to investigate the valence effect of different A-site metal ions on elemental Mn and the adsorption of reactant molecules on the surface. The results indicate that Mn atoms exhibit a variety of oxidation states and are strongly electrophilic in CrMn2O4 spinel. DFT and in situ DRIFTS were combined to reveal the reaction mechanisms of NH3-SCR and chlorobenzene oxidation. This study lays the foundation for the application of high-performance Mn-based spinel catalysts in multi-pollution abatement.

Insight into the performance of VOx-WOx/TiO2 catalysts modified by various cerium precursors: A combined study on synergistic NOx and chlorobenzene removal

Cerium is widely used as a modifier to enhance the catalytic performance of the selective catalytic reduction (SCR) catalysts due to its exceptional low-temperature properties. However, the effects of different cerium precursors on catalytic performance remains unclear. In this study, VOx-WOx/TiO2 catalysts are modified using Ce(NO3)3·6H2O (cata-N), CeO2 (cata-O), and Ce(OH)4 (cata-OH), and their synergistic removal of NOx and chlorobenzene (CB), as well as their resistance to water and sulfur poisoning, were systematically investigated. Among the tested catalysts, cata-N demonstrated superior CB (45.0-93.3 %) and NOx (31.9-90.37 %) removal efficiencies under synergistic conditions, along with excellent water resistance (T90 = 193 °C with 5 % H2O). In contrast, cata-OH exhibited the highest sulfur resistance, maintaining a denitrification efficiency of 20 % after 10 h of sulfur exposure, compared to 9 % for cata-N and 8 % for cata-O. Characterization revealed that Ce(NO3) 3·6H2O improved cerium dispersion, leading to enhanced the redox properties and acidity (especially Brønsted acid sites (BAS)) in cata-N. Density functional theory (DFT) calculations and In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTS) results revealed that the well-dispersed cerium atoms contributed additional BAS in the form of Ce-OH, while also forming Ti-O-Ce bonds. These Ti-O-Ce bonds facilitated the formation of Ti-OH on the TiO2 surface. Ti-OH significantly enhanced the adsorption of NH3 and CB, thereby promoting both the NH3-SCR and CB oxidation processes. This study offers new insights into the role of cerium precursors and provides a practical strategy for tuning BAS of catalysts in multiple pollutants removal.

Unveiling mechanistic insight into boosting oxygen species activation over CeO2/Mn2O3 p-n heterojunction for efficient photothermal mineralization of toluene

The activation mechanism of oxygen species activation (including lattice oxygen and gaseous oxygen) in the photothermal catalytic reaction process is important for boosting the efficient removal of VOCs. Herein, we have successfully synthesized a p-n heterojunction photothermal catalyst CeO2/Mn2O3 for exploring the activation of molecular oxygen and lattice oxygen in toluene catalytic reaction under full spectrum conditions. Various characterization tests and theoretical calculations showed that the formed composite has enhanced light absorption ability, oxygen species migration and transformation ability as well as nice redox cycles, which is conducive to the fast replenishment of surface lattice oxygen and continuous capture and activation of molecular oxygen. Meanwhile, the results of in-situ DRIFTS tests not only confirmed the enhanced activation process of surface lattice oxygen and molecular oxygen under the synergistic effect of light and heat, but also revealed the pathway and mechanism of photothermal catalytic toluene over CeO2/Mn2O3.

Regulating the Electronic Metal-Support Interaction of Single-Atom Ruthenium Catalysts for Boosting Chlorobenzene Oxidation

Developing highly active single-atom catalysts (SACs) with excellent chlorine resistance for efficient oxidation of harmful chlorinated volatile organic compounds (CVOCs) is a great challenge. Tuning the electronic metal-support interaction (EMSI) is viable for promoting catalytic performances of SACs. Herein, an effective strategy of modulating the EMSI in Ru1/CeO2 SACs by thermal treatment control is proposed, which distinctly enhances the activities of the catalyst for chlorobenzene (CB) oxidation and chlorine conversion, accomplishing total CB degradation at nearly 260 °C. Detailed characterization and theoretical calculations reveal that the EMSI induces electron transfer from Ru to CeO2, optimizing the coordination and electronic structure of single-atom Ru and accordingly facilitating the adsorption and activation of CB. Moreover, the surface lattice oxygen (Olatt) at the Ru-O-Ce interface is demonstrated as the critical reactive oxygen species, the mobility and reactivity of which are also prompted by the EMSI, leading to the boosted conversion of reaction intermediates. This work sheds light on the effect of EMSI regulation on CVOC catalytic oxidation and provides guidance on fabricating high-efficiency SACs for environmental catalysis.

Rationally Fabricated Ce-Mn@ZrO2-SO42- Catalyst Boosts the Efficient Destruction of Chlorobenzene with SO2 Impurity: Synergy of Surface SO42- and Acidic Sites

The catalytic deactivation caused by SO2 impurity remains a great challenge in the efficient destruction of industrial chlorinated volatile organic compounds (CVOCs). Herein, a Ce-Mn@ZrO2-SO42- catalyst with a Ce-O-Mn active system and ZrO2-SO42- protective layer was rationally engineered, which exhibits superior activity for chlorobenzene (CB) and SO2 cotreatment at 228 °C, achieving 90% CB mineralization─over 80% higher than that of the CeO2 catalyst. In situ characterization and theoretical calculation results reveal that the SO42- groups not only inhibit the adsorption of SO2 molecules through steric hindrance and electrostatic repulsion but also act as the Brønsted acid sites (BAS) to promote C-Cl cleavage of chlorobenzene (CB) and accelerate the desorption of Cl radicals as inorganic chlorine (HCl and Cl2). Additionally, the Ce-O-Mn structure accelerates electron transfer between active sites, enhances the strength of Lewis acid sites (LAS), and weakens the lattice oxygen stability to generate oxygen vacancies (Ov). These features collectively result in the excellent chlorine and sulfur resistance of the Ce-Mn@ZrO2-SO42- catalyst. Compared to CeO2 and Ce-Mn@ZrO2, chlorinated and sulfated byproducts respectively decrease by 7.9 and 2.7 times in the presence of 100 ppm SO2. This study provides a feasible and promising strategy for engineering efficacious non-noble metal catalysts toward CVOCs' deep purification with SO2 impurity, showcasing substantial economic and environmental benefits.

Chlorine-Tolerant Chlorobenzene Combustion over Mullite Catalysts via In Situ Constructing Ru-O-Mn Sites

The catalytic combustion of chlorine-containing volatile organic compounds (CVOCs) at low temperatures still faces chlorine poisoning challenges. Herein, chlorine-tolerant chlorobenzene combustion over manganese-based mullite (SmMn2O5) catalysts has been originally demonstrated via in situ constructing rich Ru-O-Mn sites, engineered from the in situ doping of ruthenium (Ru) and the subsequent etching of samarium (Sm). Such catalysts exhibited 90% activity for chlorobenzene combustion at 258 °C and maintained about 80% activity after the 30 h stability test. Specifically, the doping of Ru could readily replace Mn4+ of SmMn2O5 to form Ru-O-Mn sites, and the etching of Sm could expose more surface Ru-O-Mn sites, which significantly enhanced the redox capacity and oxygen activation ability, thus improving the low-temperature catalytic combustion of chlorobenzene. Besides, the Ru-O-Mn sites boosted the transformation of chlorine-containing intermediate species to low-pollution species and accelerated the removal of Cl and the formation of CO2, thus enhancing the chlorine tolerance of mullite catalysts. This study deepened the understanding of the catalytic combustion mechanism and provided a feasible strategy for the development of high-efficiency and chlorine-resistant catalysts for the catalytic combustion of CVOCs.

Boosting chlorobenzene oxidation over MIL-101(Cr) derived CrOx catalysts: The stepwise regulation of CrOx clusters and oxygen species by calcination atmospheres

In this work, CrOx catalysts derived from MIL-101(Cr) were prepared for the oxidation of chlorobenzene (CB). The atmosphere of calcination had great effect on the physical and chemical properties of the catalysts. Only the atmosphere of Ar could carbonize and preserve the organic ligands in the structure, retaining the micropore structure and high surface area of MIL-101(Cr). Therefore, the aggregation of CrOx clusters was prevented, forming abundant coordinative unsaturated Cr3+ and oxygen vacancies. They would transform to abundant Cr6+ as the active sites in the treatment of 10 %O2/Ar, and acid sites composed with OH and surface adsorbed oxygen were formed around Cr6+, which played an important role on the adsorption/activation of CB and the oxidation of the intermediates. Through the oxygen vacancies, the surface lattice oxygen could migrate and replenish the oxygen consumed around Cr6+. Thus, MIL-101(Cr)-Ar-T, synthesized by MIL-101(Cr) stepwise calcined in Ar and treatment of 10 %O2/Ar, exhibited the highest catalytic activity for CB oxidation with the T90 at 233 °C, and the selectivity to COx and HCl at 240 °C could reach 95.85 % and 97.61 %, respectively, with a high stable performance in the 5-day catalytic activity test.

Recent Advances of the Effect of H2O on VOC Oxidation over Catalysts: Influencing Factors, Inhibition/Promotion Mechanisms, and Water Resistance Strategies

Water vapor is a significant component in real volatile organic compounds (VOCs) exhaust gas and has a considerable impact on the catalytic performance of catalysts for VOC oxidation. Important progress has been made in the reaction mechanisms of H2O and water resistance strategies for VOC oxidation in recent years. Despite advancements in catalytic technology, most catalysts still exhibit low activity under humid conditions, presenting a challenge in reducing the adverse effects of H2O on VOC oxidation. To develop water-resistant catalysts, understanding the mechanistic role of H2O and implementing effective water-resistance strategies with influencing factors are imperative. This Perspective systematically summarizes related research on the impact of H2O on VOC oxidation, drawing from over 390 papers published between 2013 and 2024. Five main influencing factors are proposed to clarify their effects on the role of H2O. Five inhibition/promotion mechanisms of H2O are introduced, elucidating their role in the catalytic oxidation of various VOCs. Additionally, different kinds of water resistance strategies are discussed, including the fabrication of hydrophobic materials, the design of specific structures and morphologies, and the introduction of additional elements for catalyst modification. Finally, scientific challenges and opportunities for enhancing the design of efficient and water-resistant catalysts for practical applications in VOC purification are highlighted.

Constructing Bridge Hydroxyl Groups on the Ru/MOx/HZSM-5 (M = W, Mo) Catalysts to Promote the Hydrolysis Oxidation of Multicomponent VOCs

Chlorinated and oxygenated volatile organic compounds (CVOCs and OVOCs) pose a significant threat to human health. Catalytic oxidation effectively removes these pollutants, but catalyst deactivation is a challenge. Our study focused on the hydrolysis oxidation of chlorobenzene (CB) and ethyl acetate (EA) over Ru/MOx/HZSM-5 (M = W, Mo). It was found that doping MoOx to the catalyst increased the structural hydroxyl amount and balanced surface acidity, thus significantly improving the catalytic stability, with Ru/MoOx/HZSM-5 exhibiting a better activity for CB and EA oxidation (T90% = 438 and 276 °C at space velocity = 20,000 mL g-1 h-1, respectively). Water vapor introduction considerably promoted hydrolysis oxidation and protected the active sites from being poisoned by cumulative chlorine. The synergistic interaction of the Mo-O(H)-Al structure in Ru/MoOx/HZSM-5 with the Si-OH-Al structure promotes the activation of H2O to form bridging hydroxyl groups, which provide a proton-rich environment for hydrolysis oxidation. It was also found that dissociated H2O reacted with adsorbed oxygen species to form highly active *OOH, accelerating the deep oxidation of intermediates. We believe that the present study can provide a unique strategy for the effective elimination of multicomponent VOCs under complex conditions.

Selective Adsorption of Chlorine Species on RuO2 Sites for Efficient Elimination of Vinyl Chloride on the Ru/SnO2 Catalyst

The main bottleneck in the catalytic combustion of chlorinated volatile organic compounds (CVOCs) is deactivation and the production of chlorine-containing byproducts originating from the chlorine species deposited on the catalyst. Herein, Ru supported on SnO2 (Ru/SnO2) was prepared with the lattice matching principle. As RuO2 and SnO2 are both rutile phases, Ru species were present as highly dispersed RuO2 particles on the Ru/SnO2 catalyst. These particles adsorbed chlorine species with greater efficiency during the CVOCs combustion, thereby protecting the oxygen vacancies. Therefore, the double sites, oxygen vacancy to oxidize and RuO2 to adsorb chlorine species, on the Ru/SnO2 catalyst led to a notable enhancement in activity, stability, and byproduct selectivity. In contrast, the high dispersion of Ru species on the CeO2 support, as the typical catalyst for chlorinated hydrocarbon combustion, gave rise to a predominantly Ru-O-Ce structure. This structure did not prevent the adsorption of chlorine species on the oxygen vacancies, resulting in deactivation at low temperatures and an increased polychlorinated byproduct concentration. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) further corroborated the variation in the adsorption sites of chlorine species on the two catalysts. This work provides a new strategy for designing efficient Ru-based catalysts for catalytic CVOCs combustion.

Promoting C-Cl Bond Activation via a Preoccupied Anchoring Strategy on Vanadia-Based Catalysts for Multi-Pollutant Control of NOx and Chlorinated Aromatics

Regulating vanadia-based oxides has been widely utilized for fabricating effective difunctional catalysts for the simultaneous elimination of NOx and chlorobenzene (CB). However, the notorious accumulation of polychlorinated species and excessively strong NH3 adsorption on the catalysts lead to the deterioration of multipollutant control (MPC) activity. Herein, protonated sulfate (-HSO4) supported on vanadium-titanium catalysts via a preoccupied anchoring strategy are designed to prevent polychlorinated species and alleviate NH3 adsorption for the multipollutant control. The obtained catalysts with -HSO4 modification achieve an excellent NOx and CB conversion with turnover frequency values of ∼ 3.63 and 17.7 times higher than those of the pristine, respectively. The protonated sulfate promotes the formation of polymeric vanadyl with a higher chemical state and d-band center of V. The modulated catalysts not only substantially alleviate the competitive adsorption of multipollutant via the "V 3d-O 2p-S 3p" network, but also distinctly strengthen the Brønsted acid sites. Besides, the introduced proton donor of the -HSO4 connecting polymeric structure could markedly reduce the reaction barrier of breaking the C-Cl bond. This work paves an advanced way for low-loading vanadium SCR catalysts to achieve highly efficient NOx and CB oxidation at a low temperature.

Photothermal Catalytic Removal of 1,2-DCE with High HCl Selectivity over the Brønsted Acid-Enriched Sulfur-Doped MOFs

Chlorinated volatile organic compounds come from a wide range of sources and are highly toxic, posing a serious threat to biological health and the environment. Herein, a high-efficiency and energy-saving photothermal synergistic catalytic oxidation method was developed for the removal of 1,2-dichloroethane (1,2-DCE). Compared to traditional thermocatalysis, the 1,2-DCE conversion over Ru-U6S in photothermal synergistic catalysis at 340 °C increased by approximately 44% not only reducing energy consumption but also avoiding the instability of MOF structure caused by high reaction temperature. The excellent photothermal catalytic oxidation activity was derived from the synergistic effect of photo- and thermocatalysis. Ru-U6S demonstrated excellent 1,2-DCE adsorption capacity and stronger light utilization and could produce more reactive oxygen species (•OH and •O2-) after light illumination, which participated in the oxidation reaction, promoting the release of the active site of the catalyst. The results of H2O-TPD and NH3-DRIFTS exhibited that the use of S-containing ligands in the synthesis process increased the hydroxyl groups and Brønsted acid sites, significantly improved the selectivity of CO2 and HCl in the oxidation process, and reduced the release of chlorine-containing byproducts. This work provides a high-efficiency and energy-saving strategy for removing chlorinated volatile organic compounds and increasing the selectivity of ideal products directly with MOFs directly.

Simultaneous removal of naphthalene and NOx over V-Ce/Ti catalyst: Design of separated active sites for naphthalene degradation and SCR reaction

V-Ce/Ti catalysts were prepared for the removal of naphthalene and NOx in the flue gas. The adverse effects of NH3 and NO on the naphthalene degradation were weakened on V-Ce/Ti, resulting in a decrease of only 2.5 % in COx selectivity. The formation of high molecular weight byproducts was also reduced. Besides the acid sites on the catalysts, Ce introduced new Brønsted basic sites, which could also adsorb and degrade naphthalene into naphthol effectively. With the separated active sites for naphthalene degradation and NO removal, the reaction between NH3 and the intermediates during the naphthalene degradation was also inhibited, decreasing the formation and accumulation of phthalimide. The oxidation of the intermediates was promoted by active V5+ introduced by Ce, inhibiting the transformation of the intermediates to higher molecular weight byproducts. Nearly 100 % conversion of naphthalene and NO, as well as 40.1 % of the COx selectivity were obtained on V-Ce/Ti.

Constructing Pd@Layered-CoOx/MFI Bifunctional Catalyst for Efficient Ethyl Acetate Oxidation: Boosted C═O Activation and *O Species Transformation

Oxygenated volatile organic compounds (OVOCs), emitted in large quantities by the chemical industry, are a major contributor to the formation of ozone and subsequent particulate matter. For the efficient catalytic oxidation of OVOCs, the challenges of molecular activation and intermediate inhibition remain. The construction of bifunctional active sites with specific structures offers a promising way to overcome these problems. Here, the Pd@Layered-CoOx/MFI bifunctional catalyst with core-shell active sites was rationally fabricated though a two-step ligand pyrolysis method, which exhibits a superb oxidation efficiency toward ethyl acetate (EA). Over this, 13.4% of EA (1000 ppm) can be oxidized at just 140 °C with a reaction rate of 13.85 mmol·gPd-1·s-1, around 176.7 times higher than that of the conventional Pd-CoOx/MFI catalyst. The electronic coupling of the Pd-Co pair promotes the electron back-donation from Pd nanoparticles to the layered CoOx shell and facilitates the formation of Pd2+ species, which greatly enhances the adsorption and activation of the electron-rich C═O bond of the EA molecules. In addition, the synergy of these core-shell Pd@Layered-CoOx sites accelerates the activation and transformation of *O species, which inhibit the formation of acetaldehyde and ethanol byproducts, ensuring the rapid total oxidation of EA molecules via the Mars-van Krevelen mechanism. This work established a solid foundation for exploring robust bifunctional catalysts for deep OVOC purification.

Hollow Core-Shell Bismuth Based Al-Doped Silica Materials for Powerful Co-Sequestration of Radioactive I2 and CH3I

Developing pure inorganic materials capable of efficiently co-removing radioactive I2 and CH3I has always been a major challenge. Bismuth-based materials (BBMs) have garnered considerable attention due to their impressive I2 sorption capacity at high-temperature and cost-effectiveness. However, solely relying on bismuth components falls short in effectively removing CH3I and has not been systematically studied. Herein, a series of hollow mesoporous core-shell bifunctional materials with adjustable shell thickness and Si/Al ratio by using silica-coated Bi2O3 as a hard template and through simple alkaline-etching and CTAB-assisted surface coassembly methods (Bi@Al/SiO2) is successfully synthesized. By meticulously controlling the thickness of the shell layer and precisely tuning of the Si/Al ratio composition, the synthesis of BBMs capable of co-removing radioactive I2 and CH3I for the first time, demonstrating remarkable sorption capacities of 533.1 and 421.5 mg g-1, respectively is achieved. Both experimental and theoretical calculations indicate that the incorporation of acid sites within the shell layer is a key factor in achieving effective CH3I sorption. This innovative structural design of sorbent enables exceptional co-removal capabilities for both I2 and CH3I. Furthermore, the core-shell structure enhances the retention of captured iodine within the sorbents, which may further prevent potential leakage.

Phosphotungstic Acid as a Dechlorination Agent Collaborates with CeO2 for Synergistic Catalytic Elimination of NOx and Chlorobenzene

The development of efficient technologies for the synergistic catalytic elimination of NOx and chlorinated volatile organic compounds (CVOCs) remains challenging. Chlorine species from CVOCs are prone to catalyst poisoning, which increases the degradation temperature of CVOCs and fails to balance the selective catalytic reduction of NOx with the NH3 (NH3-SCR) performance. Herein, synergistic catalytic elimination of NOx and chlorobenzene has been originally demonstrated by using phosphotungstic acid (HPW) as a dechlorination agent to collaborate with CeO2. The conversion of chlorobenzene was over 80% at 270 °C, and the NOx conversion and N2 selectivity reached over 95% at 270-420 °C. HPW not only allowed chlorine species to leave as inorganic chlorine but also enhanced the Bro̷nsted acidity of CeO2. The NH4+ produced in the NH3-SCR process can effectively promote the dechlorination of chlorobenzene at low temperatures. HPW remained structurally stable in the synergistic reaction, resulting in good water resistance and long-term stability. This work provides a cheaper and more environmentally friendly strategy to address chlorine poisoning in the synergistic reaction and offers new guidance for multipollutant control.

Efficient Catalytic Elimination of Chlorobenzene Based on the Water Vapor-Promoting Effect within Mn-Based Catalysts: Activity Enhancement and Polychlorinated Byproduct Inhibition

Achieving no or low polychlorinated byproduct selectivity is essential for the chlorinated volatile organic compounds (CVOCs) degradation, and the positive roles of water vapor may contribute to this goal. Herein, the oxidation behaviors of chlorobenzene over typical Mn-based catalysts (MnO2 and acid-modified MnO2) under dry and humid conditions were fully explored. The results showed that the presence of water vapor significantly facilitates the deep mineralization of chlorobenzene and restrains the formation of Cl2 and dichlorobenzene. This remarkable water vapor-promoting effect was conferred by the MnO2 substrate, which could suitably synergize with the postconstructed acidic sites, leading to good activity, stability, and desirable product distribution of acid-modified MnO2 catalysts under humid conditions. A series of experiments including isotope-traced (D2O and H218O) CB-TPO provided complete insights into the direct involvement of water molecules in chlorobenzene oxidation reaction and attributed the root cause of the water vapor-promoting effect to the proton-rich environment and highly reactive water-source oxygen species rather than to the commonly assumed cleaning effect or hydrogen proton transfer processes (generation of active OOH). This work demonstrates the application potential of Mn-based catalysts in CVOCs elimination under practical application conditions (containing water vapor) and provides the guidance for the development of superior industrial catalysts.

The enhancement of benzene total oxidation over RuxCeO2 catalysts at low temperature: The significance of Ru incorporation

Catalytic oxidation is considered to be the most efficient technology for eliminating benzene from waste gas. The challenge is the reduction of the catalytic reaction temperature for the deep oxidation of benzene. Here, highly efficient RuxCeO2 catalysts were utilized to turn the number of surface oxygen vacancies and Ce-O-Ru bonds via a one-step hydrothermal method, resulting in a preferable low-temperature reducibility for the total oxidation of benzene. The T50 of the Ru0.2CeO2 catalyst for benzene oxidation was 135 °C, which was better than that of pristine CeO2 (239 °C) and 0.2Ru/CeO2 (190 °C). The superior performance of Ru0.2CeO2 was attributed to its large surface area (approximately 114.23 m2·g-1), abundant surface oxygen vacancies, and Ce-O-Ru bonds. The incorporation of Ru into the CeO2 lattice could effectively facilitate the destruction of the CeO bond and the facile release of lattice oxygen, inducing the generation of surface oxygen vacancies. Meanwhile, the bridging action of Ce-O-Ru bonds accelerated electron transfer and lattice oxygen transportation, which had a synergistic effect with surface oxygen vacancies to reduce the reaction temperature. The Ru0.2CeO2 catalyst also exhibited high catalytic stability, water tolerance, and impact resistance in terms of benzene abatement. Using in situ infrared spectroscopy, it was demonstrated that the Ru0.2CeO2 catalyst can effectively enhance the accumulation of maleate species, which are key intermediates for benzene ring opening, thereby enhancing the deep oxidation of benzene.

Accelerated Catalytic Ozonation in a Mesoporous Carbon-Supported Atomic Fe-N4 Sites Nanoreactor: Confinement Effect and Resistance to Poisoning

The design of a micro-/nanoreactor is of great significance for catalytic ozonation, which can achieve effective mass transfer and expose powerful reaction species. Herein, the mesoporous carbon with atomic Fe-N4 sites embedded in the ordered carbon nanochannels (Fe-N4/CMK-3) was synthesized by the hard-template method. Fe-N4/CMK-3 can be employed as nanoreactors with preferred electronic and geometric catalytic microenvironments for the internal catalytic ozonation of CH3SH. During the CH3SH oxidation process, the mass transfer coefficient of the Fe-N4/CMK-3 confined system with sufficient O3 transfer featured a level of at least 1.87 × 10-5, which is 34.6 times that of the Fe-N4/C-Si unconfined system. Detailed experimental studies and theoretical calculations demonstrated that the anchored atomic Fe-N4 sites and nanoconfinement effects regulated the local electronic structure of the catalyst and promoted the activation of O3 molecules to produce atomic oxygen species (AOS) and reactive oxygen species (ROS), eventually achieving efficient oxidation of CH3SH into CO2/SO42-. Benefiting from the high diffusion rate and the augmentation of AOS/ROS, Fe-N4/CMK-3 exhibited an excellent poisoning tolerance, along with high catalytic durability. This contribution provides the proof-of-concept strategy for accelerating catalytic ozonation of sulfur-containing volatile organic compounds (VOCs) by combining confined catalysis and atomic catalysts and can be extended to the purification of other gaseous pollutants.

Insights into synergistic oxidation mechanism of Hg0 and chlorobenzene over MnCo2O4 microsphere with oxygen vacancy and acidic site

The simultaneous control of Hg⁰ and chlorinated organics has become the frontier of environmental engineering but still lacks the understanding of synergistic oxidation mechanism. Herein, we designed a Mn-Co catalyst with abundant oxygen vacancies and acidities, which delivered more than 90 % oxidation performance of Hg⁰ within 100-325 °C and achieved 90 % conversion of chlorobenzene at 220 °C. A synergistic effect was observed in the oxidation of Hg⁰ and chlorobenzene. Experimental and computational results revealed that Lewis acid over Mn site weakened C-Cl bands of chlorobenzene by electronic traction. The strong interaction between adsorbed mercury and Cl further promoted dechlorination process to generate HgCl₂ gas, while accelerating the nucleophilic substitution of Brønsted acid attacking the benzene ring over Co site, consequently triggering synergistic oxidation of Hg⁰ and chlorobenzene. Oxygen vacancies enhanced the initial adsorption of Hg⁰ and chlorobenzene. Meanwhile, the interfacial charge-transfer from Hg-d to Cl-p orbitals alleviated deactivation of Lewis acid and slowed down the consumption of Brønsted acid, which accelerated the conversion of intermediates to CO₂/H₂O and promoted deep oxidation of chlorobenzene. This work provides a unique insight into the promotion of the synergistic oxidation of Hg⁰ and chlorobenzene and is expected to guide the industrial applications.

Pt/CeO2 coated with polyoxometallate chainmail to regulate oxidation of chlorobenzene without hazardous by-products

Doping noble metal and acid functionalization were both valid approaches to facilitate oxidation of chlorobenzene on CeO₂-based catalysts, but their promotion effects were influenced by different orders of modification process. Because of strong interaction between metal and support and proper redox nature of CeO₂, Pt NPs were re-dispersed into single atoms on CeO₂ surface via "ex-solution". Companied with Pt loading, the enhancement of oxidizing ability led to generation of polychlorinated by-products. Herein, CeO₂-supported Pt was coated by HSiW chainmail to protect Pt from being exposed to Cl-contained atmosphere, and HSiW coating promoted activation of chlorobenzene. The as-prepared chainmail catalyst of HSiW/Pt/CeO₂ displayed a remarkable performance in catalyzing oxidation of chlorobenzene without any dichlorobenzene at realistic condition. By comparison, other catalysts with exposed Pt suffered from production of toxic by-products.

Simultaneously Constructing Active Sites and Regulating Mn-O Strength of Ru-Substituted Perovskite for Efficient Oxidation and Hydrolysis Oxidation of Chlorobenzene

Chlorinated volatile organic compounds (CVOCs) are a class of hazardous pollutants that severely threaten environmental safety and human health. Although the catalytic oxidation technique for CVOCs elimination is effective, enhancing the catalytic efficiency and simultaneously inhibiting the production of organic byproducts is still of great challenge. Herein, Ru-substituted LaMn(Ru)O_{3+ δ} perovskite with Ru-O-Mn structure and weakened Mn-O bond strength has been developed for catalytic oxidation of chlorobenzene (CB). The formed Ru-O-Mn structure serves as favorable sites for CB adsorption and activation, while the weakening of Mn-O bond strength facilitates the formation of active oxygen species and improves oxygen mobility and catalyst reducibility. Therefore, LaMn(Ru)O_{3+ δ} exhibits superior low-temperature activity with the temperature of 90% CB conversion decreasing by over 90 °C compared with pristine perovskite, and the deep oxidation of chlorinated byproducts produced in low temperature is also accelerated. Furthermore, the introduction of water vapor into reaction system triggers the process of hydrolysis oxidation that promotes CB destruction and inhibits the generation of chlorinated byproducts, due to the higher-activity *OOH species generated from the dissociated H₂ O reacting with adsorbed oxygen. This work can provide a unique, high-efficiency, and facile strategy for CVOCs degradation and environmental improvement.

Rationally Engineering a CuO/Pd@SiO2 Core-Shell Catalyst with Isolated Bifunctional Pd and Cu Active Sites for n-Butylamine Controllable Decomposition

Volatile organic amines are a category of typical volatile organic compounds (VOCs) extensively presented in industrial exhausts causing serious harm to the atmospheric environment and human health. Monometallic Pd and Cu-based catalysts are commonly adopted for catalytic destruction of hazardous organic amines, but their applications are greatly limited by the inevitable production of toxic amide and NO_x byproducts and inferior low-temperature activity. Here, a CuO/Pd@SiO₂ core-shell-structured catalyst with diverse functionalized active sites was creatively developed, which realized the total decomposition of n-butylamine at 260 °C with a CO₂ yield and N₂ selectivity reaching up to 100% and 98.3%, respectively (obviously better than those of Pd@SiO₂ and CuO/SiO₂), owing to the synergy of isolated Pd and Cu sites in independent mineralization of n-butylamine and generation of N₂, respectively. The formation of amide and short-chain aliphatic hydrocarbon intermediates via C-C bond cleavage tended to occur over Pd sites, while the C-N bond was prone to breakage over Cu sites, generating NH₂· species and long free-N chain intermediates at low temperatures, avoiding the production of hazardous amide and NO_x. The SiO₂ channel collapse and H⁺ site production resulted in the formation of N₂O via suppressing NH₂· diffusion. This work provides critical guidance for a rational fabrication of catalysts with high activity and N₂ selectivity for environmentally friendly destruction of nitrogen-containing VOCs.

Vinyl chloride catalytic combustion on Pt/CeO2: Tuning Pt chemical state to promote Cl removing

Supported Pt catalysts usually produce chlorinated byproducts during chlorinated volatile organic compounds (CVOCs) combustion, the removal of formed surface chlorine species is the key to improve the activity, selectivity and stability. In this paper, the Pt chemical state is adjusted by the interaction between Pt and CeO₂ through controlling the morphology of CeO₂, which further affects the catalytic performance of VC combustion. For Pt/CeO₂-octahedron, the weak interaction between Pt and CeO₂ results in the formation of PtO₂, facilities VC adsorption and C-Cl bonds cleavage and becomes a key active site to accommodate the dissociated Cl species. While the strong interaction leads to the formation of Pt_xCe_1-xO_2-σ solid solution on Pt/CeO₂-rod has relative lower ability in Cl species removal compared with PtO₂. Density functional theory (DFT) calculations also confirms that the introduced Pt species reduces the concentration of Cl species on the surface as well as the chlorinated-byproducts. Hence, Pt/CeO₂-octahedron outperformed Pt/CeO₂-rod and Pt/CeO₂-cube with 90% VC conversion at 280 °C. Furthermore, under the same VC conversion (90%), the concentration of chlorinated byproducts on Pt/CeO₂-octahedron was only 4% than that of Pt/CeO₂-rod.

Evaluation of the Flexibility for Catalytic Ozonation of Dichloromethane over Urchin-Like CuMnOx in Flue Gas with Complicated Components

The evaluation of the poisoning effect of complex components in practical gas on DCM (dichloromethane) catalytic ozonation is of great significance for enhancing the technique's environmental flexibility. Herein, Ca, Pb, As, and NO/SO₂ were selected as a typical alkaline-earth metal, heavy metal, metalloid, and acid gas, respectively, to evaluate their interferences on catalytic behaviors and surface properties of an optimized urchin-like CuMn catalyst. Ca/Pb loading weakens the formation of oxygen vacancies, oxygen mobility, and acidity due to the fusion of Mn-Ca/Pb-O, leading to their inferior catalytic performance with poor CO₂ selectivity and mineralization rate. Noticeably, the presence of As induces excessively strong acidity, facilitating the inevitable formation of byproducts. Catalytic co-ozonation of NO/DCM is achieved with stoichiometric ozone addition. Unfortunately, SO₂ introduction brings irreversible deactivation due to strong competition adsorption and the loss of active sites. Unexpectedly, Ca loading protects active sites from an attack by SO₂. The formation of unstable sulfites and the released Mn-O structure offset the negative effect from SO₂. Overall, the catalytic ozonation of DCM exhibits a distinctive priority in the antipoisoning of metals with the maintenance of DCM conversion. The construction of more stable acid sites should be the future direction of catalyst design; otherwise, catalytic ozonation should be arranged together with post heavy metal capture and a deacidification system.

Catalytic ozonation of CH2Cl2 over hollow urchin-like MnO2 with regulation of active oxygen by catalyst modification and ozone promotion

This paper firstly reported efficient catalytic ozonation of CH₂Cl₂ (dichloromethane, DCM) at low temperature over hollow urchin-like MnO₂ with high chlorine resistance. Regulations on morphologies and Cu doping, as well as ozone promotion were conducted to optimize active oxygen of MnO₂ catalysts, contributing to excellent catalytic behaviors. Cu doping MnO₂ with hollow urchin-like morphology attained a stable 100% DCM conversion with O₃/DCM molar ratio of 10 at 120 °C. The ozone utilization rate, final products, and byproducts distribution were discussed. Abundant crystal defects, low-valance Mn/Cu, O_ads, and weak acidity, as well as better low temperature reducibility contributed to its superior performance. During DCM catalytic ozonation, DCM oxidation exhibited competitive effect on O₃ decomposition due to the occupation of intermediates (CH₂ClO₃·, O-CH₂Cl, and O-CH₂ -O) over active sites that should belong to O₃ originally. Nevertheless, O₃ decomposition exhibited synergistic effects on DCM oxidation with promotion on active oxygen. Density functional theory (DFT) calculations confirmed the positive effect on oxygen vacancy formation and O₃/DCM adsorption from Cu doping. The possible mechanism for DCM catalytic ozonation included four parts, including O₃/DCM adsorption, O₃ activation, DCM oxidation, and electron replenishment. This paper provides new insight for catalytic elimination of chlorinated alkanes at mild conditions.

Engineering Platinum Catalysts via a Site-Isolation Strategy with Enhanced Chlorine Resistance for the Elimination of Multicomponent VOCs

Pt-based catalysts can be poisoned by the chlorine formed during the oxidation of multicomponent volatile organic compounds (VOCs) containing chlorinated VOCs. Improving the low-temperature chlorine resistance of catalysts is important for industrial applications, although it is yet challenging. We hereby demonstrate the essential catalytic roles of a bifunctional catalyst with an atomic-scale metal/oxide interface constructed by an intermetallic compound nanocrystal. Introducing trichloroethylene (TCE) exhibits a less negative effect on the catalytic activity of the bimetallic catalyst for o-xylene oxidation, and the partial deactivation caused by TCE addition is reversible, suggesting that the bimetallic, HCl-etched Pt₃Sn(E)/CeO₂ catalyst possesses much stronger chlorine resistance than the conventional Pt/CeO₂ catalyst. On the site-isolated Pt-Sn catalyst, the presence of aromatic hydrocarbon significantly inhibits the adsorption strength of TCE, resulting in excellent catalytic stability in the oxidation of the VOC mixture. Furthermore, the large amount of surface-adsorbed oxygen species generated on the electronegative Pt is highly effective for low-temperature C-Cl bond dissociation. The adjacent promoter (Sn-O) possesses the functionality of acid sites to provide sufficient protons for HCl formation over the bifunctional catalyst, which is considered critical to maintaining the reactivity of Pt by removing Cl and decreasing the polychlorinated byproducts.