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.

It is an intractable issue to improve the low-temperature SO2-tolerant selective catalytic reduction (SCR) of NO x with NH3 because deposited sulfates are difficult to decompose below 300 °C. Herein, we established a low-temperature self-prevention mechanism of mesoporous-TiO2@Fe2O3 core–shell composites against sulfate deposition using experiments and density functional theory. The mesoporous TiO2-shell effectively restrained the deposition of FeSO4 and NH4HSO4 because of weak SO2 adsorption and promoted NH4HSO4 decomposition on the mesoporous-TiO2. The electron transfer at the Fe2O3 (core)-TiO2 (shell) interface accelerated the redox cycle, launching the “Fast SCR” reaction, which broadened the low-temperature window. Engineered from the nano- to macro-scale, we achieved one-pot self-installation of mesoporous-TiO2@Fe2O3 composites on the self-tailored AlOOH@Al-mesh monoliths. After the thermal treatment, the mesoporous-TiO2@Fe2O3@Al2O3 monolith catalyst delivered a broad window of 220–420 °C with NO conversion above 90% and had superior SO2 tolerance at 260 °C. The effective heat removal of Al-mesh monolithcatalysts restrained NH3 oxidation to NO and N2O while suppressing the decomposition of NH4NO3 to N2O, and this led to much better high-temperature activity and N2 selectivity. This work supplies a new point for the development of low-temperature SO2-tolerant monolithic SCR catalysts with high N2 selectivity, which is of great significance for both academic interests and practical applications.

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Catalytic combustion of volatile organic compounds (VOCs) at low temperatures is still an urgent issue to be solved. Herein, low-temperature combustion of toluene over Cu-doped SmMn 2 O 5 mullite catalysts via creating highly active Cu 2+ −O− Mn 4+ sites has been originally demonstrated. Cu-doped SmMn 2 O 5 mullite catalysts exhibited 90% conversion of toluene at 206 °C and displayed robust stability even in the presence of water. It has been demonstrated that Cu doping created Cu 2+ −O−Mn 4+ active composite sites that were more exposed after removing surface Sm species via acid-etching. Benefiting from this, the redox and oxygen activation ability of catalysts was significantly enhanced. The consumption of benzaldehyde and benzoic acid as intermediate species and the CO 2 generation ability were apparently promoted, which were the direct reasons for the enhanced low-temperature combustion of toluene. This work provides novel ideas for the development of high-performance catalysts for low-temperature VOC combustion, which has great industrial application prospects.

Selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR) is an efficient NO x abatement strategy, but deNO x catalysts suffer from serious deactivation due to the coexistence of multiple poisoning substances such as K, SO2, etc. in the flue gas. It is essential to understand the interaction among various poisons and their effects on NO x abatement. Here, we unexpectedly identified the K migration behavior induced by SO2 over K-poisoned FeVO4/TiO2 catalysts, which led to alkali-poisoning buffering and activity recovery. It has been demonstrated that the K would occupy both redox and acidic sites, which severely reduced the reactivity of FeVO4/TiO2 catalysts. After the sulfuration of the K-poisoned catalyst, SO2 preferred to be combined with the surface K2O, lengthened the K–OFe and K–OV, and thus released the active sites poisoned by K2O, thereby preserving an increase in the activity. As a result, for the K-poisoned catalyst, the conversion of NO x increased from 21 to 97% at 270 °C after the sulfuration process. This work contributes to the understanding of the specific interaction between alkali metals and SO2 on deNO x catalysts and provides a novel strategy for the adaptive use of one poisoning substance to counter another for practical NO x reduction.