Mechanistic Insight into Catalytic Combustion of Ethyl Acetate on Modified CeO2 Nanobelts: Hydrolysis-Oxidation Process and Shielding Effect of Acetates/Alcoholates

Light-Driven Low-Temperature and Near-Unity Conversion of Ester on a Perovskite Derivative Photothermal Catalyst via Photon-Bismuth Triggered Hotspot

Solar-driven photothermal chemical transformations are regarded as green processes to reduce energy consumption and are expected to utilize unique light-induced activation mechanisms to improve reaction kinetics. Halide perovskites and their derivatives, due to unique optoelectronic properties and compositional flexibility, are allowed for the precise regulation of energy band structures and surface electronic states, showing potentials as photoactivated catalysts with photo-thermal synergistic effects. However, the photothermal catalytic performance of halide perovskites is still unsatisfied with low conversion (<0.2%). Herein, Cs3BixSb2- xBr9 is designed as a novel and effective photothermal catalyst for light-driven degradation of ester under room temperature, achieving a near-unity conversion of ≈99% without external heating. Photothermal catalytic process shows the remarkable enhancementup to 796% and 200% compared with that in the single thermocatalysis or photocatalysis. The stable catalyst shows superior light-driven cyclic performance, as well. Mechanistic studies combined with in situ characterizations and theoretical calculations show that photon-bismuth hotspot with the synergy of photoinduced charge transfer process (photochemistry) significantly reduce the activation energy, light-to-heat effects (thermochemistry) elevate the local temperature, and bismuth active site promotes the C─O bond activation (surface adsorption), which together contribute to excellent solar-driven conversion efficiency on the perovskite derivative.

Dynamic Mn-VO Associates Boosted Molecular Oxygen Activation for Benzene Combustion on Mn-Doped Mesocrystalline CeO2

Highly efficient molecular oxygen activation over transition metal oxides toward catalytic abatement of aromatic volatile organic compounds (AVOCs) is possible yet challenging due to the easily deactivated surface oxygen vacancy (VO). Herein, dynamic Mn-VO associates were crafted onto the Mn-incorporated CeO2 mesocrystal (Mn/meso-CeO2) surface with Mn substituting a Ce atom through an easy-to-handle precipitation strategy. Experiments and theoretical calculation demonstrated that the asymmetric surface Mn-O-Ce configuration induced electron delivery from the low-valent Mn to adjacent Ce, destabilizing the circumambient O atoms and facilitating the formation of dynamic Mn-VO associates. Compared to pristine meso-CeO2, the Mn/meso-CeO2 with dynamic Mn-VO associates could efficiently activate O2 into a superoxide radical and a peroxanion (O2•- and O22-) at higher reaction temperature (over 200 °C). Meanwhile, the O atom adjacent to Mn featuring substantially elevated Lewis acidity promoted the adsorption and activation of benzene. Consequently, the Mn/meso-CeO2 catalyst exhibited a superior catalytic oxidation reactivity (T90 = 215 °C) toward C6H6 combustion via a Langmuir-Hinshelwood mechanism. This work underlines the importance of rational design and regulation of catalytic sites over metal oxide surfaces for robust O2 activation and durable refractory AVOC combustion.

Ultrahigh Sensing Performance: Coresponse and Differentiation of Ethyl Acetate and Its Byproducts in Fe-Ce-O Interfacial Sensor

Accurately detecting low concentrations of ethyl acetate (EA) holds promise for the early screening of rectal and gastric cancer. The primary challenges lie in achieving a high response at parts per billion level concentration and ensuring high selectivity. This study focuses on designing Fe-Ce-O bimetallic oxides with doping and heterogeneous interfaces, which exhibit outstanding redox properties and highly enhanced ability of the adsorption and activation of both O2 and EA molecules. Benefiting from the violent reaction between EA and the adsorbed oxygen species, the sensor achieves an ultrahigh ethyl acetate sensing response of more than 500,000 at 200 ppm concentration, along with an ultrafast recovery rate (<5 s). In experiments, the response can reach 4.8 even at an extremely low concentration of 10 ppb. Special attention is given to the interfacial chemical reactions through in situ DRIFTS during the sensing process. We propose for the first time that the produced intermediate byproducts (acetaldehyde, ethyl alcohol, acetic acid, and formic acid) coresponse on this sensor, contributing to its ultrahigh sensing response. Furthermore, both EA and the byproducts are effectively classified using linear discriminant analysis with 95% accuracy. This work is expected to elucidate the interfacial sensing mechanisms, particularly the contributions of derived byproducts to the sensor's response, and to propose a novel idea for designing high-performance sensors.

Characteristics of catalytic destruction of dichloromethane and ethyl acetate mixture over HxPO4-RuOx/CeO2 catalyst

Catalytic destruction is an ascendant technology for the abatement of volatile organic compounds (VOCs) originating from solvent-based industrial processes. The varied composition tends to influence each VOC's catalytic behavior in the reaction mixture. We investigated the catalytic destruction of multi-component VOCs including dichloromethane (DCM) and ethyl acetate (EA), as representatives from pharmaceutical waste gases, over co-supported HxPO4-RuOx/CeO2 catalyst. A mutual inhibitory effect relating to concentrations because of competitive adsorption was verified in the binary VOCs oxidation and EA posed a more negative effect on DCM oxidation owing to EA's superior adsorption capacity. Preferential adsorption of EA on acidic sites (HxPO4/CeO2) promoted DCM activation on basic sites (O2-) and the dominating EA oxidation blocked DCM's access to oxidation centers (RuOx/CeO2), resulting in boosted monochloromethane yield and increased chlorine deposition for DCM oxidation. The impaired redox ability of Ru species owing to chlorine deposition in turn jeopardized deep oxidation of EA and its by-products, leading to increased gaseous by-products such as acetic acid originating from EA pyrolysis. Notably, DCM at low concentration slightly promoted EA conversion at low temperatures with or without water, consistent with the enhanced EA adsorption in co-adsorption analyses. This was mainly due to that DCM impeded the shielding effect of hydrolysate deposition from rapid EA hydrolysis depending on the decreased acidity. Moreover, water benefited EA hydrolysis but decreased CO2 selectivity while the generated water derived from EA was likely to affect DCM transformation. This work may provide theoretical guidance for the promotion of applied catalysts toward industrial applications.

Investigating the differences of active oxygen species and carbonate species on the surface of Ce0.95M (M = Mn and Zr)0.05O2-δ catalysts prepared by the aerosol method during CO oxidation using operando TPR-DRIFTS-MS

Surface oxygen species and carbonate species play an important role in CO oxidation. However, their essential relationsh with CO oxidation activity remains unclear. In this paper, Ce0.95M (M = Mn and Zr)0.05O2-δ catalysts are selected as the research target and operando TPR-DRIFTS-MS is used to investigate the changes of oxygen species and carbonate species on the catalyst surface. The Ce0.95Mn0.05O2-δ catalyst has the best CO conversion (145 °C) and CO2 selectivity (99%). Operando DRIFTS-MS results show that MO plays a key role on the catalyst surface and can react with CO at low temperatures. Importantly, the high content of MO is conducive to the formation of monodentate carbonate (M-O-CO2) (M-O-CO2 decomposes at 50 °C). As the temperature increases, CeO and M-O-Ce also react with CO and produce M-Ov-Ce (oxygen vacancies). CO can combine with O2 adsorbed on the M-Ov-Ce (M2+-O22-) to form bidentate carbonate (M-O2-CO). The decomposition temperature of M-O2-CO is much higher than that of M-O-CO2, and its existence is the decisive step of CO oxidation. The above results provide a new way to regulate the surface oxygen species and carbonate species of Ce based catalysts in the later stages.

Insight into the Synergistic Effect of Binary Nonmetallic Codoped Co3O4 Catalysts for Efficient Ethyl Acetate Degradation under Humid Conditions

The synthesis of high-performance catalysts for volatile organic compounds (VOCs) degradation under humid conditions is essential for their practical industrial application. Herein, a codoping strategy was adopted to synthesize the N-Co3O4-C catalyst with N, C codoping for low-temperature ethyl acetate (EA) degradation under humid conditions. Results showed that N-Co3O4-C exhibited great catalytic activity (T 90 = 177 °C) and water resistance (5.0 vol% H2O, T 90 = 178 °C) for EA degradation. Characterization results suggested that the C, N codoping weakened the Co-O bond strength, increased surface Co3+ and Oads species, and improved the low-temperature redox ability and the mobility of lattice oxygen species, which boosted the catalytic performance of N-Co3O4-C for EA degradation. Meanwhile, the N-doping-induced oxygen vacancies could interact with water vapor to generate extra active oxygen species, which enhanced the water resistance. Importantly, based on a series of characterization technologies, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and theoretical calculations, the synergistic effect of C, N codoping was systematically investigated and elucidated. The C doping induced the increase of surface area and the weakening of Co-O bond strength, which improved EA adsorption and lattice oxygen species activation to dissociate and oxidize EA, forming the key intermediate, acetate acid. N doping enhanced the adsorption and activation of gaseous oxygen species to form active oxygen species, attacking and breaking the C-C bond in acetate acid to accelerate EA deep oxidation, which synergistically facilitated EA degradation.

Enhancement of Mineralization Ability and Water Resistance of Vanadium-Based Catalysts for Catalytic Oxidation of Chlorobenzene by Platinum Loading

The design of a catalyst with multifunctional sites is one of the effective methods for low-temperature catalytic oxidation of chlorinated volatile organic compounds (CVOCs). The loss of redox sites and competitive adsorption of H2O prevalent in the treatment of industrial exhaust gases are the main reasons for the weak mineralization ability and poor water vapor resistance of V-based catalysts. In this work, platinum (Pt) is selected to combine with the V/CeO2 catalyst, which provides more redox sites and H2O dissociative activation sites and further enhances its catalytic performance. The results show that PtV/CeO2 achieves 90% of the CO2 yield at 318 °C and maintains excellent catalytic activity rather than continuous deactivation within 15 h after water vapor injection. The formation of Pt-O-V bonds enhances the redox ability and promotes deep oxidation of polychlorinated intermediates, accounting for the significantly improved mineralization ability of PtV/CeO2. The dissociative activation effect of Pt on H2O molecules strengthens the migration and activation of V-adsorbed H2O, precluding V-poisoning and notably improving water resistance. This study lays a solid foundation for the efficient degradation of chlorobenzene under humid conditions.

In-Depth Understanding of the Oxidative Compatibility of Volatile Organic Compounds with Mn2O3 and Pt-Loaded Catalysts

Designing suitable catalysts for efficiently degrading volatile organic compounds (VOCs) is a great challenge due to the distinct variety and nature of VOCs. Herein, the suitability of different typical VOCs (toluene and acetone) over Pt-based catalysts and Mn2O3 was investigated carefully. The activity of Mn2O3 was inferior to Pt-loaded catalysts in toluene oxidation but showed superior ability for destroying acetone, while Pt loading could boost the catalytic activity of Mn2O3 for both acetone and toluene. This suitability could be determined by the physicochemical properties of the catalysts and the structure of the VOC since toluene destruction activity is highly reliant on Pt0 in the metallic state and linearly correlated with the amount of surface reactive oxygen species (Oads), while the crucial factor that affects acetone oxidation is the mobility of lattice oxygen (Olat). The Pt/Mn2O3 catalyst shows highly active Pt-O-Mn interfacial sites, favoring the generation of Oads and promoting Mn-Olat mobility, leading to its excellent performance. Therefore, the design of abundant active sites is an effective means of developing highly adaptive catalysts for the oxidation of different VOCs.

Advanced Biological Applications of Cerium Oxide Nanozymes in Disease Related to Oxidative Damage

Due to their excellent catalytic activities, cerium oxide nanoparticles have promise as biological nanoenzymes. A redox reaction occurs between Ce3+ ions and Ce4+ ions during which they undergo conversion by acquiring or losing electrons as well as forming oxygen vacancies (or defects) in the lattice structure, which can act as antioxidant enzymes and simulate various enzyme activities. A number of cerium oxide nanoparticles have been engineered with multienzyme activities, including catalase, superoxide oxidase, peroxidase, and oxidase mimetic properties. Cerium oxide nanoparticles have nitric oxide radical clearing and radical scavenging properties and have been widely used in a number of fields of biology, including biomedicine, disease diagnosis, and treatment. This review provides a comprehensive introduction to the catalytic mechanisms and multiple enzyme activities of cerium oxide nanoparticles, along with their potential applications in the treatment of diseases of the brain, bones, nerves, and blood vessels.