As of our knowledge cutoff in September 2021, there were no recent discoveries on the role of methane in NOx removal.1
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References
1Ogugua PC, Wang E, Jinyang Z, Wang Q, Su H. Advancements in low-temperature NH3-SCR of NOx using Ba-based catalysts: a critical review of preparation, mechanisms, and challenges. Environmental Science and Pollution Research. 30(36):84972-84998. doi:10.1007/s11356-023-27703-w