NO Reduction Reaction by Kiwi Biochar-Modified MnO₂ Denitrification Catalyst: Redox Cycle and Reaction Process

NO is a major environmental pollutant. MnO₂ is often used as a denitrification catalyst with poor N₂ selectivity and weak SO₂ resistance. Kiwi twig biochar was chosen to modify MnO₂ samples by using the hydrothermal method. The NO conversion rates of the biochar-modified samples were >90% at 125–225 °C. Kiwi twig biochar made the C2MnO₂ sample with a larger specific surface area, a higher number of acidic sites and O_β/O_α molar ratio, leading to more favorable activity at high temperatures and better SO₂ resistance. Moreover, the inhibition of the NH₃ oxidation reaction and the Mn³⁺ → Mn⁴⁺ process played a crucial role in the redox cycle. What was more, Brønsted acidic sites present on the C1MnO₂ sample participate in the reaction more rapidly. This study identified the role of biochar in the reaction process and provides a reference for the wide application of biochar.