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Catalytic decomposition of aromatic polluters at room temperature represents a green route for air purification but is currently challenged by the difficulty of generating reactive oxygen species (ROS) on catalysts. Herein, we develop a mullite catalyst YMn2O5(YMO) with dual active sites of Mn3+and Mn4+and use ozone to produce a highly reactive O* upon YMO. Such a strong oxidant species on YMO shows complete removal of benzene from −20 to >50 °C with a high COxselectivity (>90%) through the generated reactive species O* on the catalyst surface (60 000 mL g–1h–1). Although the accumulation of water and intermediates gradually lowers the reaction rate after 8 h at 25 °C, a simple treatment by ozone purging or drying in the ambient environment regenerates the catalyst. Importantly, when the temperature increases to 50 °C, the catalytic performance remains 100% conversion without any degradation for 30 h. Experiments and theoretical calculations show that such a superior performance stems from the unique coordination environment, which ensures high generation of ROS and adsorption of aromatics. Mullite’s catalytic ozonation degradation of total volatile organic compounds (TVOC) is applied in a home-developed air cleaner, resulting in high efficiency of benzene removal. This work provides insights into the design of catalysts to decompose highly stable organic polluters.

Large ambient temperature changes (−20–>25 °C) bring great challenges to the purification of the indoor pollutant formaldehyde. Within such a large ambient temperature range, we herein report a manganese-based strategy, that is, a mullite catalyst (YMn2O5) + ozone, to efficiently remove the formaldehyde pollution. At −20 °C, the formaldehyde removal efficiency reaches 62% under the condition of 60,000 mL gcat–1h–1. As the reaction temperature is increased to −5 °C, formaldehyde and ozone are completely converted into CO2, H2O, and O2, respectively. Such a remarkable performance was ascribed to the highly reactive oxygen species generated by ozone on the YMn2O5surface based on the low temperature-programed desorption measurements. The in situinfrared spectra showed the intermediate product carboxyl group (−COOH) to be the key species. Based on the superior performance, we built a consumable-free air purifier equipped with mullite-coated ceramics. In the simulated indoor condition (25 °C and 30% relative humidity), the equipment can effectively decompose formaldehyde (150 m3h–1) without producing secondary pollutants, rivaling a commercial removal efficiency. This work provides an air purification route based on the mullite catalyst + ozone to remove formaldehyde in an ambient temperature range (−20–>25 °C).

Exploring the effect of interfacial structural properties on catalytic performance of hybrid materials is essential in rationally designing novel electrocatalysts with high stability and activity. Here, in situ growth of mullite SmMn2O5on nitrogen-doped reduced graphene oxide (SMO@NrGO) is achieved for highly efficient oxygen reduction reaction (ORR). Combining X-ray photoelectron spectroscopy and density functional theory calculations, interfacial chemical interactions between Mn and substrates are verified. Interestingly, as revealed by charge density difference, the interfacial Mn–N(C) bonds display a sponge effect to store and compensate electrons to boost the ORR process. In addition, bidentate adsorption of oxygen intermediates instead of monodentate ones is observed in hybrid materials, which facilitates the interactions between intermediates and active sites. Experimentally, the hybrid catalyst SMO@NrGO exhibits a half-wave potential as high as 0.84 V, being comparable to benchmark Pt/C and higher than that of the pure SMO (0.68 V). The Zn–air battery assembled with SMO@NrGO shows a high discharge peak power density of 244 mW cm–2and superior cycling stability against noble metals.

Developing transition metal compound (TMC) catalysts is complicated by the intricate relationship between their crystal and electronic structures and their catalytic performance. To address this challenge, we propose the “from active unit to catalyst” (FAUC) strategy starting with optimizing the physical property of a Mn-centered [MnO6] entity to ensure its catalytic performance. These entities are then arranged to reveal how their assembly influences the electronic structures. Notably, a two-dimensional (2D) entity-formed lattice shows a promising low theoretical overpotential (0.08 V) for oxygen reduction reaction due to the optimal occupied orbital position. According to the catalytic requirements of an individual entity and its stacking modes, we further developed a search algorithm to identify three-dimensional (3D) structures from 154,718 candidates, pinpointing CaMnO3as the most effective one among the screened candidates. This FAUC approach provides a comprehensive framework for designing catalysts from basic units to complex assemblies.

The strong adsorption of water molecules at the active site of the catalyst presents significant challenges in ozone decomposition, particularly at room temperature and in humid environments. To address this issue, we doped carbon atoms into the Mn-mullite YMn2O5catalyst to replace oxygen, resulting in efficient and stable ozone decomposition under highly humid conditions. Utilizing DFT calculations, our study demonstrated that carbon doping disrupts hydrogen bond networks on the catalyst surface, thereby reducing water adsorption. Furthermore, carbon doping regulated the electronic structure of active sites, fundamentally reversing the adsorption strength of water and ozone molecules, which avoids the decline in catalytic activity caused by competitive water adsorption. Experimentally, under room temperature and relative humidity (RH) 50%, the carbon-doped YMn2O5catalyst maintained 100% conversion in decomposing 100 ppm of ozone for at least 24 h, surpassing the most reported catalysts against water poisoning. Furthermore, the utilization of a carbon-doped mullite-loaded air cleaner demonstrated promising application in degrading ozone. The approach of enhancing catalyst water resistance through carbon doping, which disrupts hydrogen bonds, provided valuable insights into the design of stable and efficient room-temperature ozonolysis catalysts.

Interface engineering is one of the key strategies to modify the intrinsic electronic structures of catalysts and consequently improve the electrochemical activity of the oxygen reduction reaction (ORR) in the cathodes of the energy conversion devices such as fuel cells and metal-air batteries. Herein, we proposed the mixed-phase mullite (AxSm1−xMn2O5-δ, x = 0–0.5, A=Ca, Sr, Ba), prepared by facile one-step co-precipitation method, to catalyze the oxygen reduction reaction (ORR). The X-ray diffraction (XRD) spectra show that each mixture includes three phases, i.e., mullite SmMn2O5, O-deficient perovskite AMnO3-δand MnOx. Atomic bonding interfaces are formed between SmMn2O5and AMnO3-δ, based on the observations of the high resolution transmission electron microscopy (HRTEM). Among these different mixed-phase samples, we find that BaxSm1−xMn2O5-δ/C exhibits the best ORR catalytic activity with the half-wave potential ~ 0.79 V (vs. RHE) and the highest stability over 20,000 s. This performance can be ascribed to the largest charge transfer from BaMnO2.83to SmMn2O5. Subsequently, partial Mn4+in mullite SmMn2O5phase are reduced to active sites Mn3+to achieve the egunit occupancy in the interfacial depletion region. In comparison with the reactions over pure-phase mullite SmMn2O5,these transferred electrons are involved into ORR and thus accelerate the proceeding. Our work thus provides insights into designing heterogeneous compound catalysts via interfacing engineering in the applications of the electrochemical oxygen reactions.

The rationally designed vacancy-modified heterostructured FeMoSx/CoNiPxelectrocatalyst shows excellent OER performance due to modulated electron structure and reaction kinetics by vacancy introduction and heterojunction formation, presenting great promising applications in seawater splitting and Zn-air battery.