Theoretical and experimental study on the N₂O reduction by H2 over char decorated with transition metal at low temperatures

In this study, a catalytic system for N2O reduction by H(2 )onto char decorated with transition metals is proposed, which have excellent reduction efficiency at low temperatures below 200 C and efficiently utilizes pyrolysis char and hydrogen. Density functional theory (DFT) is used to reveal the reaction mechanism and found that transition metal decoration can significantly promote reaction rate and decrease the activation energy required for N2O reduction by H-2 on char, from 383.7 kJ/mol to 50-160 kJ/mol. Furthermore, transition states in the process of reducing N2O by H-2 over metal-char were observed, including reduction of N2O and the removal of the surface oxygen complex. Through kinetic analysis, the activation energy and reaction rate order was found as Ni-char (50.0 kJ/mol)>Co-char (95.1 kJ/mol)>Fe-char (151.0 kJ/mol)>Cu-char (158.8 kJ/mol). According to experiments phenomenon, the sequence of reduction efficiency over different metal-char was consistent with the simulation results and it was even possible to convert N2O to N-2 below 200 celcius. This research contributes to a more mechanistic understanding of the N2O-H-2 reaction over char and provides new insights for improving the design of catalysts for N2O abatement at low temperatures.