Al-Decorated C₂N Monolayer as a Potential Catalyst for NO Reduction with CO Molecules: A DFT Investigation

Developing efficient and economical catalysts for NO reduction is of great interest. Herein, the catalytic reduction of NO molecules on an Al-decorated C₂N monolayer (Al-C₂N) is systematically investigated using density functional theory (DFT) calculations. Our results reveal that the Al-C₂N catalyst is highly selective for NO, more so than CO, according to the values of the adsorption energy and charge transfer. The NO reduction reaction more preferably undergoes the (NO)₂ dimer reduction process instead of the NO direct decomposition process. For the (NO)₂ dimer reduction process, two NO molecules initially co-adsorb to form (NO)₂ dimers, followed by decomposition into N₂O and O_ads species. On this basis, five kinds of (NO)₂ dimer structures that initiate four reaction paths are explored on the Al-C₂N surface. Particularly, the cis-(NO)₂ dimer structures (D_cis-N and D_cis-O) are crucial intermediates for NO reduction, where the max energy barrier along the energetically most favorable pathway (path II) is as low as 3.6 kcal/mol. The remaining O_ads species on Al-C₂N are then easily reduced with CO molecules, being beneficial for a new catalytic cycle. These results, combined with its low-cost nature, render Al-C₂N a promising catalyst for NO reduction under mild conditions.