Effect of CaO on the selectivity of N2O decomposition products: A combined experimental and DFT study

- Calcium oxide decreases the NO selectivity from N2O decomposition compared to N2O homogeneous decomposition.
- N2 has a much higher selectivity from N2O decomposition compared to NO for both homogeneous and CaO-catalyzed N2O decomposition.
- The NO formation on the CaO (1 0 0) surface is likely to proceed via the reaction between a surface adsorbed atomic O and a gaseous N2O molecule.

The effect of CaO on N2O decomposition and the selectivity of its decomposition products (NO and N2) was investigated using a fixed-bed flow reactor with varying temperatures from 317 °C to 947 °C. The selectivity of NO from CaO-catalyzed N2O decomposition is much lower than the N2 selectivity with the N2/NO products ratio greater than 12.1. Compared to N2O homogeneous decomposition with the minimum N2/NO products ratio of 6.2 at 718 °C, CaO also decreases the NO selectivity from 718 °C to 947 °C. Density functional theory calculations provide possible N2O decomposition routes on the CaO (1 0 0) surface considering both N2 and NO as N2O decomposition products. The N2 formation route is more favorable than the NO formation route in terms of energy barrier and reaction energy, and NO formation on the CaO (1 0 0) surface is likely to proceed via N2O + Osurf2- → N2 + O2 , surf2- and N2O + O2 , surf2- → 2NO + Osurf2-.

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