Abundant Oxygen Vacancies Induced by the Mechanochemical Process Boost the Low-Temperature Catalytic Performance of MnO2 in NH3-SCR

Manganese oxides (MnOx) have attracted particular attention in the selective catalytic reduction of NOx with NH3 (NH3-SCR) because of their excellent low-temperature activity. Herein, we prepared a highly efficient MnO2 (MnO2-M) catalyst through a facile ball milling-assisted redox strategy. MnO2-M shows a 90% NOx conversion in a wide operating temperature window of 75-200 degrees C under a gas hourly space velocity of 40,000 h(-1), which is much more active than the MnO2 catalyst prepared by the redox method without the ball-milling process. Moreover, MnO2-M exhibits better H2O and SO2 resistance. The enhanced catalytic properties of MnO2-M originated from the high surface area, abundant oxygen vacancies, more acid sites, and higher Mn4+ content induced by the ball-milling process. In situ DRIFTS studies probed the reaction intermediates, and the SCR reaction was deduced to proceed via the typical Eley-Rideal mechanism. This work provides a facile method to enhance the catalytic performance of Mn-based catalysts for low-temperature denitrification and deep insights into the NH3-SCR reaction process.

Automated summary

This study prepares a highly active manganese oxide catalyst (MnO2-M) through a ball milling-assisted redox strategy, which shows higher catalytic activity compared to the catalyst without the ball milling process. MnO2-M exhibits excellent catalytic performance in a wide temperature range and has better resistance to water and sulfur dioxide.