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The catalytic oxidation of volatile organic compounds (VOCs) is considered a feasible method for VOCs treatment by virtue of its low technical cost, high economic efficiency, and low additionally produced pollutants, which is of important social value. Single-atom catalysts (SACs) with 100% atom utilization and uniform active sites usually have high activity and high product selectivity, and promise a broad range of applications. Precise regulation of the microstructures of SACs by means of defect engineering, interface engineering, and electronic effects can further improve the catalytic performance of VOCs oxidation. In this review, we introduce the mechanisms of VOCs oxidation, and systematically summarize the recent research progress of SACs in catalytic VOCs total oxidation into CO2 and H2O, and then discuss the effects of various structural regulation strategies on the catalytic performance. Finally, we summarize the current problems yet to be solved and challenges currently faced in this field, and propose future design and research ideas for SACs in catalytic oxidation of VOCs. [ABSTRACT FROM AUTHOR]

Determining the effect of crystal facets on reaction performance is essential for designing an efficient propane oxidation catalyst. Herein, α-MnO2 nanowires with exposed (110), (211), (310) and (200) facets were proposed, and their crystal facet-dependent reactivity to propane oxidation was investigated. The resultant α-MnO2 nanowires with predominantly exposed (110) facets showed the maximum propane oxidation activity (T90 = 262.1 °C), oxidation rate, and turnover frequency (at 230 °C), and high stability during the oxidation of propane. In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the oxidation to form carboxylates is the decisive step; therefore, the production of reactive oxygen species is very important. The results from density of states computations revealed that the lowest electron energy was present in the (110) facet, which helps in the generation of reactive oxygen species and the regulation of the surface valence of Mn. The characterization and calculation results indicated that the (110) facets are conducive to forming oxygen vacancies, which allowed the activation and adsorption of O2 and propane, resulting in significantly enhanced propane oxidation activity. Apart from offering new insights about the structure–activity relationship of α-MnO2 with different facets exposed for short-chain volatile oxidation reactions, this study proposes a technique that can be used for improving other manganese-based catalyst oxidation systems. [ABSTRACT FROM AUTHOR]

Ceria (CeO2) has been regarded as one of the most promising industrial catalysts for hydrochloric acid (HCl) oxidation to replace RuO2‐based catalysts. Thermal sintering and chlorination of CeO2 limit its large‐scale application. In this work, ultrafine CeO2 nanodots embedded in a porous ZrO2 matrix (CeO2@ZrO2) are successfully prepared by a spontaneous deposition method and evaluated in HCl catalytic oxidation for sustainable Cl2 recycle. The physicochemical properties of CeO2@ZrO2 catalysts are characterized by means of XRD, Raman, SEM, TEM, BET, XPS, H2‐TPR and oxygen storage capacity (OSC). The results reveal that all CeO2@ZrO2 catalysts display large specific surface area, pore volume, perfect low‐temperature reduction performance and oxygen storage‐release capacity. More importantly, the unique structure of the CeO2 nanodots isolated by amorphous ZrO2 improves the dispersion and inhibits the sintering of active sites. The optimized 40CeO2@ZrO2 catalyst reveals superior activity (1.90 gCl2 ⋅ gcat−1 ⋅ h−1) and good durability (100 h under 430 °C). Kinetic studies reveal that the adsorption of O2 and HCl is competitive at the active sites, and the desorption of surface Cl is the rate‐determining step. [ABSTRACT FROM AUTHOR]

In this study, highly‐dispersed perovskite‐type oxides LaMnxCo1‐xO3 supported on mesoporous SiO2 (LMxC1‐xO/SiO2) were synthesized by a citric acid‐assisted deposition method. For LMxC1‐xO/SiO2 catalysts, the double B‐site transition metal ions can not only significantly arise the surface defects, but also lead to the formation of (Mn3++Co3+)/(Co2++Mn4+) redox cycle, both of which were able to improve the catalytic performance of LMxC1‐xO/SiO2 in n‐butylamine combustion. Strikingly, LM0.2C0.8O/SiO2 catalyst showed the optimum catalytic performance (T90%=210 °C at a space velocity of 15,000 mL gcat−1 h−1) and the lowest NOx yield among the LMxC1‐xO/SiO2 samples, which could be greatly assigned to the accelerated activation and circulation of the oxygen species initiated by the surface defects and redox cycle. [ABSTRACT FROM AUTHOR]

A series of Ce-Ti mixed oxides (Ce a Ti 1−a ) were successfully synthesized by a spontaneous deposition method and evaluated in selective catalytic reduction of NO with NH 3 (NH 3 -SCR). The structures and properties of the Ce a Ti 1−a catalysts were characterized by means of XRD, Raman, TEM, N 2 -sorption, XPS, H 2 -TPR and NH 3 -TPD. The results demonstrated that lots of Ce-O-Ti species were formed because of the strong synergistic interaction of gelation of TiO 2 and deposition of Ce 3+ during the preparation process of Ce a Ti 1−a catalysts. As results, the Ce a Ti 1−a catalysts exhibited excellent redox ability, enrichment of Ce 3+ species, high surface adsorbed oxygen concentration, and abundant acid sites. The Ce a Ti 1−a catalysts showed remarkable catalytic activity with broad operation temperature window, and Ce 0.5 Ti 0.5 catalyst exhibited the best catalytic activity and extraordinary H 2 O/SO 2 durability. The in-situ FTIR results revealed that the mechanisms of L-H and E-R existed synchronously during the NH 3 -SCR reaction, and the former one was predominant due to its rapid reaction rate. [ABSTRACT FROM AUTHOR]

• MOFs derived Ni@ZrO 2 catalysts were facilely prepared by tunable strategy. • Nickle precursor impregnated Zr-mofs (Ni/ZrO 2 -B catalyst) shows the highest DRM performance. • Physico-chemical properties including ni species, ZrO 2 matrix, and interface interaction were strongly affected by preparation strategy. • Strong metal-support interaction is responsible for superior catalytic performance. Metal-support interaction (MSI) plays an important role in heterogeneous catalysis, that could be well regulated by many strategies. Here, Ni@ZrO 2 catalysts were controllably synthesized by sacrificial Zr-MOFs template strategy, and were applied to the dry reforming of methane (DRM). Amongst, the Ni/ZrO 2 -B catalyst shows the best performance toward CH 4 and CO 2 conversion, H 2 /CO ratio, and stability, following by Ni/ZrO 2 -A and Ni/ZrO 2 C catalysts. The difference in catalytic performance should be ascribed to different synthetic strategy, resulting in different properties of Ni species and ZrO 2 matrix, and interface interaction. It revealed that small Ni particles were benefit for CH 4 activation, and strong MSI boosted CO 2 activation, that could remain the Ni dispersion and thermal stability. This study is beneficial to the catalyst design in DRM reaction. A Metal-Organic Frameworks (MOFs) strategy was proposed to assist the preparation of supported Ni/ZrO 2 catalyst. The embedded structure and strong metal-support interaction endow it with superior performance in dry reforming of methane (DRM). [Display omitted] [ABSTRACT FROM AUTHOR]

Ultrafine cobalt oxide nanoparticles embedded in porous SiO 2 matrix were facilely prepared by a spontaneous deposition method, which were applied to catalytic methane combustion. Owing to rich surface active oxygen and more active sites, the CoO x @SiO 2 -400 catalyst shows the highest catalytic activity. These structural catalyst also show high thermal stability and efficient moisture resistance. [Display omitted] • Ultrafine cobalt oxide nanoparticles embedded in porous SiO2 matrix were facilely prepared. • The CoOx@SiO2-400 catalyst with the smallest particle size (˜1.3 nm) shows the highest activity. • Rich surface adsorbed oxygen and more active sites contribute to higher activity. • These structural catalysts show high thermal stability and efficient moisture resistance. Ultrafine cobalt oxide nanoparticles embedded in porous SiO 2 matrix were facilely prepared by a spontaneous deposition method, which were applied to catalytic methane combustion. Among the serial of CoO x @SiO 2 -T catalysts, the CoO x @SiO 2 -400 catalyst with the smallest particle size (˜1.3 nm) has the highest activity, showing an obvious size-dependent activity. Based on the XPS, O 2 -TPD and H 2 -TPR analyses, it indicated that the CoO x @SiO 2 -400 catalyst possessed a higher ratio of surface absorbed oxygen and lattice oxygen (O ads /O latt) and more active sites, which enabled the enhancement of its catalytic activity. Compared with simply supported CoO x /SiO 2 -400 catalyst, the embedded CoO x @SiO 2 -400 catalyst show superior catalytic performance under dry/moisture conditions owing to silica encapsulation. As for possible CH 4 combustion mechanism, the intermediate of Co-formate is determined by in-situ DRIFTS. [ABSTRACT FROM AUTHOR]

The hollow structural MnCoO x catalysts were prepared by self-assemble method using metal−organic frameworks as sacrificial template. Compared with MnCoO x nanoparticles synthesized by co-precipitation method, the hollow MnCoO x nanocages showed higher performance toward toluene oxidation, which was attributed to the high surface area, more active sites and better redox ability. After the addition of Pt species, the catalytic performance of hollow Pt/MnCoO x -H nanocages were greatly boosted, which was superior to the contrast Pt/MnCoO x -N catalyst. It revealed that the synergistic effect between Pt and support mainly contributes to improved activity, as well as the enhanced surface-active oxygen and low-temperature redox ability. In addition, the superior thermal stability was also demonstrated under dry or moisture conditions. This further promotes a potential application in the mitigation of VOCs pollution. • Pt-modified hollow structural MnCoO x nanocages were facilely prepared. • The hollow structural catalysts have high surface area, good redox ability and more active sites. • The Pt/MnCoO x -H sample shows the best catalytic performance (T 90 = 204 °C). • The synergistic effect between Pt and MnCoO x support profoundly affects the catalytic activity. [ABSTRACT FROM AUTHOR]

Plasma-treatment strategy has become an important technique to modify heterogenous catalyst. Here, the plasma-treated Ru/CeO 2 catalysts were synthesized and applied to dichloroethane (DCE) oxidation. Compared with the untreated catalysts (CeO 2 -T and Ru/CeO 2 -T), the plasma-treated catalysts (CeO 2 -P, Ru/CeO 2 -P and Ru/CeO 2 -TP) show higher catalytic activity. Amongst, the Ru/CeO 2 -P catalyst shows the highest activity (T 90 =243 °C, TOF SSA =6.98 μmol·m−2·h−1 and E a =26 kJ·mol−1). Based on various characterizations, it reveals that the plasma-treatment can enrich the concentration of surface oxygen vacancies, promote the formation of acid sites, and strengthen the interaction between Ru and CeO 2 support. The interaction benefits the dispersion of Ru species, forming more active sites to enhance the DCE conversion. The more acid sites can improve the HCl selectivity. Moreover, the Ru/CeO 2 -P catalyst exhibits excellent thermal stability and water-resistance performance. This signification result promotes the development of catalysts by plasma-treated strategy, and its wide application in heterogenous catalysis. [Display omitted] • Supported Ru/CeO 2 catalysts were prepared by plasma-assisted strategy. • The Ru/CeO 2 -P catalyst showed excellent performance for DCE oxidation. • Plasma-treatment promotes the formation of surface defects and Brønsted acid, and Ru dispersion. • The high redox capacity and strong Ru-CeO 2 interaction benefit to the superior activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dopant of Ag on MnCeO x promotes the catalytic activity for propane oxidation. • Ag dopant increases Mn4+ and Ce3+ concentrations. • Ag dopant enhances surface oxygen migration capability. • Ag dopant leads to a novel carboxylate formation path. The development of highly active catalysts for eliminating volatile organic compounds (VOCs) at low temperature is desirable but remains challenging. In this study, a series of Ag-loaded MnCeO x catalysts were fabricated. Catalysts with an Ag loading of 5 wt% exhibited the highest catalytic activity (T 90 = 242 °C) and excellent stability in H 2 O, NO 2 , and CO atmosphere. Characterization results revealed that the introduction of Ag increased Mn4+ and Ce3+ concentrations and enhanced surface oxygen migration capability, which is conducive to the adsorption and dissociation of propane and O 2. Combining in-situ diffuse reflectance infrared Fourier transform and discrete Fourier transform calculation revealed a novel propane oxidation pathway on MnCeO x and Ag/MnCeO x. The addition of Ag species can convert propane into propylene in the initial stage and reduce the activation energy. This study supplied a novel insight into Ag-doped catalysts catalytic mechanism for VOCs oxidation reaction. [ABSTRACT FROM AUTHOR]

The low defect content and poor oxygen mobility of perovskite catalysts limit its application in VOC elimination. Herein, we report a strategy involving defect engineering route following an easy urea treatment method to enhance the propane oxidation performance of perovskite catalysts. The constructed LaCoO 3 -D43 exhibits superior catalytic activity (T 90 = 309.3 °C), the T 90 value is 150 °C lower than that of LaCoO 3 , and excellent thermal stability against CO 2 and H 2 O. Experimental results revealed that the urea pyrolysis resulted in the generation of La and O defects and rich surface-active Co species in high-valence states, increasing the utilization of Co active sites. DFT calculations show that the exposed Co surface is conducive to the adsorption and dissociation of oxygen and propane. This work provides a defect engineering strategy to effectively activate perovskite catalysts performance, and can be generalized for the fabrication of other types of perovskite catalysts. [Display omitted] • Urea treatment for the fabrication of defect engineering-modified LaCoO 3 perovskite surface. • Defect engineering improved the catalytic activity during propane oxidation. • Defect engineering improved the extent of utilization of Co active sites. • Defect engineering promoted the generation of active oxygen species. [ABSTRACT FROM AUTHOR]

The acid-catalyzed Markovnikov addition of isobutene is affected by the concomitant isobutene oligomerization. Herein, a solid acid catalyst consisting of the sulfonated silica modified with crystalline ZrSiO 4 was prepared, and the ZrSiO 4 /SiO 2 -SO 3 H catalyst went beyond conventional acid catalysts in the hydroacetoxylation of isobutene. The structure of the catalyst was well-characterized, and the role of ZrSiO 4 in suppressing the dimerization of isobutene was discussed in terms of both kinetic study and in-situ DRIFT analysis. Moreover, this catalyst also showed general applicability for a broad substrate scope, further highlighting the necessity of ZrSiO 4 in the solid acid catalyst. Unlabelled Image • ZrSiO 4 /SiO 2 -SO 3 H exhibits 94% selectivity and 76% yield of tert -butyl acetate. • The ZrSiO 4 in catalyst can suppress the isobutene dimerization. • ZrSiO 4 /SiO 2 -SO 3 H is widely applicable for the isobutene hydroacetoxylation. [ABSTRACT FROM AUTHOR]