Researchers from the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences, with colleagues from University of Jinan, have developed a novel electrification strategy to improve NO_x removal performance at low temperatures.

The study was published in Environmental Science & Technology.

NO_x storage reduction (NSR) is a promising approach to control NO_x emissions from diesel vehicles. However, due to the improvement of engine technologies and frequent idling in traffic, the exhaust temperatures are usually below 250 °C, which is too low for catalytic NO_x conversion to occur.

To address this issue, the researchers developed a novel electrified NSR strategy. Pt and K co-supported antimony-doped tin oxides (Pt-K/ATO) serve as conductive catalysts. Using C₃H₆ as a reductant, a low input power (0.5-4 W) was applied to the catalyst to trigger NSR reactions.

The procedure of electrified NO_x storage–reduction. (Image by NIMTE)

With this strategy, the ignition temperature for 10% NO_x conversion was reduced to 165 °C—nearly 100 °C lower than that of the traditional thermal counterpart.

To optimize the power configuration, the fuel-lean power was reduced, resulting in a 23% increase in the maximum energy efficiency.

In addition, the electrically driven release of lattice oxygen from the catalysts is shown to play crucial roles in the NSR reactions, including promoting NO oxidation for NO_x adsorption, O₂ evolution for NO_x desorption, as well as C₃H₆ activation for NO_x reduction, thus greatly improving the NSR performance.

As reported in the previous work of the research group, this effect has also been applied to the catalytic soot combustion, demonstrating its certain universality.

This electrification strategy may shed light on the design of hybrid vehicles, especially on the development of electronic control units, since the electric power input can be adjusted in real time to reduce exhaust pollutants.

The study was supported by the by the Zhejiang Provincial Natural Science Foundation of China, the Ningbo Municipal Natural Science Foundation of China, and the Postdoctoral Science Foundation of China.

Resources

• Xueyi Mei, Ying Xin, Yexin Zhang, Weiming Nie, Zhenghui Zhang, Peng Lu, Zhaoliang Zhang, Guoxin Chen, and Jian Zhang (2023) “Electrification-Enhanced Low-Temperature NO_x Storage–Reduction on Pt and K Co-Supported Antimony-Doped Tin Oxides” Environmental Science & Technology 57 (49), 20905-20914 doi: 10.1021/acs.est.3c05354