Controllable synthesis of 3D hierarchical Co3O4 catalysts

Their excellent catalytic performance for toluene combustion

Significance 

Volatile organic compounds, high pollutant substances, have posed a significant threat to both the environment and human health. To this note, different technologies have been developed for its removal. Among them, low catalytic combustion has been identified as a promising solution owing to its low operating temperature and eco-friendly nature. This approach, however, requires the use of highly efficient catalytic materials for enhanced catalytic combustion. Unlike noble metal-based catalysts, transition metal oxides such as Co3O4 exhibiting good catalytic activities for certain volatile organic compounds have been researched. Their catalytical performance has been mainly associated with the exposed crystal plane and their morphologies. Additionally, previous findings have shown that Co3O4 catalysts with three-dimensional hierarchical morphology outperform the traditional Co3O4 materials as far as the catalytic combustion of volatile organic compounds concerned. Despite the several research work about the design and synthesis of Co3O4 catalysts, few studies have been reported about the synthesis of three-dimensional hierarchical catalysts for toluene combustion, unfortunately.

To this note, researchers at the Shenyang University of Chemical Technology: Wei Liu (Ph.D.), Rui Liu (Ph.D. student), and led by Professor Xuejun Zhang reported a controllable synthesis of the three-dimensional hierarchical Co3O4 catalysts and presented a detailed investigation of their catalytic performance for toluene combustion. The three-dimensional hierarchical Co3O4 catalysts were synthesized with different morphologies and with preferentially exposed planes, the primary factors affecting their catalytic performance. Their work is published in the research journal, Applied Surface Science.

Unlike most of the previous synthesis methods, the authors here employed a facile, surfactant- and template-free method. Two samples: S-160 and U exposed to different planes, were specifically prepared and compared. Various techniques were employed to investigate the properties of the as-obtained Co3O4 catalysts and examine the relationship between the structure and properties of Co3O4 catalysts.

The results confirmed that the catalytic performance of the Co3O4 catalysts highly depends on their morphologies. The S-160 sample exposed to {1 1 0} planes exhibited high catalytic performance than the U sample exposed to the {1 1 1} planes. S-160 sample achieved a total toluene conversion of T50% at 234°C, which was significantly lower than those of the other samples making it the best catalyst. Interestingly, the authors also noted that the morphology of the synthesized catalysts could be tuned, i.e., from urchin- to shale, by simply changing the synthesis temperature. Apart from the highly reactive {1 1 0} planes, the excellent catalytic performance of the S-160 sample could also be attributed to highly defective structure, good redox property, and rich oxygen species. Furthermore, the S-160 sample exhibited remarkable stable toluene removal efficiency.

In summary, the study presented a facile and eco-friendly morphology-controlled synthesis and application of three-dimensional hierarchical Co3O4 catalysts. Among three catalysts, the S-160 sample with dominantly exposed {1 1 0} planes exhibited the best catalytic performance of the total oxidation of toluene. Additionally, it showed a stable activity for the efficient removal of toluene during the tests under the provided conditions. In a statement to Advances in Engineering, Professor Xuejun Zhang said their research provides important know-how that would see the development of Co3O4 catalysts, specifically the S -160 sample, for practical oxidation of toluene.

Reference

Liu, W., Liu, R., & Zhang, X. (2020). Controllable synthesis of 3D hierarchical Co3O4 catalysts and their excellent catalytic performance for toluene combustion. Applied Surface Science, 507, 145174.

Go To Applied Surface Science

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