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Defect manipulation in metal oxide is of great importance in boosting catalytic performance for propane oxidation. Herein, a selective atom removal strategy was developed to construct a defective manganese oxide catalyst, which involved the partial etching of a Mg dopant in MnOx. The resulting MgMnOx-H catalysts exhibited superior low-temperature catalytic activity (T50 = 185 °C, T90 = 226 °C) with a propane conversion rate of 0.29 μmol·gcat.−1·h−1 for the propane oxidation reaction, which is 4.8 times that of pristine MnOx. Meanwhile, a robust hydrothermal stability was guaranteed at 250 °C for 30 h of reaction time. The comprehensive experimental characterizations revealed that the catalytic performance improvement was closely related to the defective structures including the abundant (metal and oxygen) vacancies, distorted crystals, valence imbalance, etc., which prominently weakened the Mn-O bond and stimulated the mobility of surface lattice oxygen, leading to the elevation in the intrinsic oxidation activity. This work exemplifies the significance of defect engineering for the promotion of the oxidation ability of metal oxide, which will be valuable for the further development of efficient non-noble metal catalysts for propane oxidation. [ABSTRACT FROM AUTHOR]

Defects are pivotal to endow metal oxide catalysts with an efficient catalytic oxidation ability. Here, a defect engineering strategy was developed by hand-milling Co3O4 with the aid of Na at room temperature. The facile mechanical–chemical process could kill two birds with one stone: on the one hand, shatter the bulk, and on the other hand create vast oxygen vacancies, which play an important role for surface exposure and intrinsic reactivity enhancement. The as-obtained defective Co3O4 catalyst delivered a remarkable activity for methane combustion with 50% methane conversion temperature (T50) of 383 °C and 90% methane conversion temperature (T90) of 459 °C, which are 47 °C and 35 °C lower than those of the pristine Co3O4 catalyst, respectively. The catalytic performance improvement could be due to the significantly increased amount of active surface oxygen and boosted oxygen mobility induced by the construction of defects. This study provides effective and convenient tactics to afford advanced catalysts for methane activation and other oxidative reactions. [ABSTRACT FROM AUTHOR]

Development of an effective Co3O4 material as an advanced non-noble metal catalyst for methane combustion has great economic and environmental significance. Herein, a facile acid etching procedure is adapted to engineer a defective Co3O4 possessing both highly exposed surface defects and lattice defects such as abundant oxygen vacancies. The defective structures facilitate an elevated exposure of active surface oxygen and enhanced redox properties. Meanwhile, the acid treatment endows a more acidic surface, which will promote the desorption of the CO2 product. Consequently, an improved activity for methane combustion with a half methane conversion temperature (T50) of 311 °C (33 000 mL g−1 h−1) is obtained for the defective Co3O4, corresponding to the methane conversion rate of 4.1 μmol g−1 s−1, 5.2 times that of the pristine Co3O4. The universality of this strategy is further verified towards a MnO2 catalyst. This study will provide positive guidance for non-noble metal catalyst design in the application of methane combustion. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient Co 3 O 4 catalyst is engineered by Mg doping and partial de -doping. • The obtained catalyst shows multiple surface and structure defects. • The defective Co 3 O 4 could lower the HCHO activation energy barrier. • Excellent HCHO oxidation activity is achieved over the defective Co 3 O 4. The pursuit of high-performance non-precious metal catalysts for Volatile Organic Compounds (VOCs) abatement is paramount in meeting stringent environmental regulations. In this study, we present a groundbreaking approach by crafting a highly defective Co 3 O 4 catalyst through a strategic process involving Mg doping and subsequent partial de- doping. The catalyst exhibited an exceptional activity in the oxidation of formaldehyde (HCHO), achieving a remarkable conversion rate of 2.92 μmol·m−2·h−1, which is 3.1 times that of the pristine Co 3 O 4 at 100 °C and an HCHO space velocity of 75,000 mL·g−1·h−1. Our methodology involves a dual-action process of doping and de- doping, orchestrating the introduction of significant structural and surface defects. These include surface cracks, lattice distortions, cationic vacancies, oxygen vacancies, lower metal coordination, and more. This orchestrated creation of defects serves to amplify the generation of active oxygen sites, thereby enhancing the intrinsic oxidative ability of the catalyst. The net result is a lowered activation energy barrier for HCHO, further contributing to the catalyst performance enhancement. This study not only establishes a new benchmark for Co 3 O 4 catalysis but also provides insightful paradigms for the role of defects engineering in promoting non-noble metal-catalyzed volatile organic compounds oxidation. [ABSTRACT FROM AUTHOR]

• A defective and N-doped Co 3 O 4 exposed with (110) facets is synthesized. • The obtained catalyst shows excellent activity for methane oxidation reaction. • The defective structure faciliates Co 3 O 4 with abundant active surface oxygen. • N doping plays important role of enhancing the C–H bond activation ability. Development of non-noble metal catalyst for low-temperature methane oxidation is extremely important yet is still a challenge. Here, we construct a defective N-doped Co 3 O 4 by a facial N 2 plasma engraving method. The obtained catalyst exhibits excellent catalytic activity with methane conversion rate of 6.5 μmol g−1 s-1 at reaction temperature of 342 °C and space velocity of 46,800 mL g−1 h−1, which is about 7.3 times that of pristine Co 3 O 4 , and is among the highest active non-noble metal catalyst. The catalyst also shows high stability under hydrothermal environment. By systematic characterization and theory calculations, the superior performance could be attributed to the defective structure, enhanced redox property and highly exposed active sites. Meanwhile, N doping plays significant role in activating Co 3 O 4 by improving the electrophilicity of surface oxygen and lowering C–H bond activation energy. The study will bring significative insight into the design of advanced Co 3 O 4 catalysts for methane oxidation. [ABSTRACT FROM AUTHOR]

Defects engineering in metal oxide is an important avenue for the promotion of VOCs catalytic oxidation. Herein, the influence of crystal facet of Co 3 O 4 is first investigated for the propane oxidation. An intelligent Cu doping is subsequently performed in the most active (110) facet exposed Co 3 O 4 catalyst. The optimized Cu-Co 3 O 4 -110–3 catalyst exhibits a prominently enhanced activity with propane conversion rate of 1.9 μmol g−1 s−1 at reaction temperature of 192 °C and the propane mass space velocity of 60,000 mL g−1 h−1, about 2.4 times that of the pristine Co 3 O 4. Systematic experimental characterizations (XAS, EPR, Raman, TPR, XPS, etc.) combined with density functional theory calculations point out that the incorporated Cu could increase the electrophilicity of nearby O atom and implant beneficial defect structures (lattice distortion, coordination unsaturation, abundant oxygen vacancies, etc.), which could significantly activate Co-O bond in Co 3 O 4 , leading to the facilitated generation of active oxygen species as well as promoted oxidation ability. This study could set an illuminating paradigm for the boost of the intrinsic oxidation activity by the precise defect construction in Co 3 O 4 catalyst, which will help drive ahead the pursuit of non-precious metal catalyst for VOCs abatement. [Display omitted] • (110) facet of Co 3 O 4 is more active for propane oxidation than other facet exposed ones. • Cu doping in (110) facet of Co 3 O 4 help further boost the propane oxidation activity. • Cu doping can stimulate Co-O activation by defect structure engineering and O electrophilicity modulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-defective NiCo 2 O 4 was constructed by a facile mechano-chemical method. • More oxygen vacancy, increased exposed active oxygen and enhanced oxygen mobility were achieved. • A remarkable oxidation activity was achieved with propane conversion rate 6 times that of Co 3 O 4. High-performance non-noble metal catalyst development is always the pursuit for the VOCs oxidation. Herein, a multi-defective spinel catalyst was intelligently built with a mechano-chemical strategy by Na assisted milling of NiCo 2 O 4 , wherein, the incorporation of Ni into the spinel oxide could introduce cationic defects, the etching by Na brought anionic defects, while the milling process fractured the bulk and facilitated the exposure of surface defects. Thereout, the obtained D-NiCo 2 O 4 was endowed with a significantly elevated oxygen vacancies, raised active oxygen species, enhanced oxygen mobility and an increased specific surface area. The beneficial features promise D-NiCo 2 O 4 a superb activity for propane catalytic oxidation, exhibiting a T 50 (temperature at 50% propane conversion) of 187 °C and T 90 (temperature at 90% propane conversion) of 194 °C at propane space velocity of 60,000 mL·g−1·h−1, which outperformed that of pristine NiCo 2 O 4 and Co 3 O 4 catalyst, making itself one of the most outstanding non-noble metal catalysts for propane oxidation. This work set the paradigm to enhance the VOCs oxidation performance of metal oxide catalyst by multi-defects engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • The anion defective Co 3 O 4 is successfully engineered by N doping. • N doped Co 3 O 4 showed a toluene conversion rate 6.8 times that of pristine Co 3 O 4. • N doping could promote active oxygen generation and enhance the oxygen reactivity. Development of advanced metal oxide catalysts for volatile organic compounds (VOCs) abatement is of great environmental and economic importance. Herein, a defective Co 3 O 4 catalyst is delineated via N doping. The anionic defects engineering significantly facilitated the oxygen vacancies formation, leading to a distorted lattice structure, increased active surface oxygen and enhanced oxygen mobility of Co 3 O 4 catalyst. These features promise an excellent toluene oxidation performance with 50% toluene conversion temperature (T 50) of 208 °C and 90 % toluene conversion temperature (T 90) of 218 °C at a space velocity of 60,000 mL g−1h−1, about 33 °C and 53 °C lower than that of the pristine Co 3 O 4 , respectively. Meanwhile, the N doped Co 3 O 4 catalyst maintains a high hydrothermal stability at 210 °C. This work exemplifies the significance of anionic defects for the intrinsic catalytic oxidation ability improvement, providing a guidance for the upgradation of the metal oxide for the application of VOCs catalytic degradation and beyond. [ABSTRACT FROM AUTHOR]