Al- or Si-decorated graphene oxide: A favorable metal-free catalyst for the N2O reduction

Abstract

The structural and catalytic properties of Al- or Si-decorated graphene oxide (Al-/Si-GO) are studied by means of density functional theory calculations. The relatively large adsorption energy together with the small AlO or SiO binding distances indicate that the epoxy groups over the GO surface can strongly stabilize the single Al or Si atom. Hence, Al-GO and Si-GO are stable enough to be utilized in catalytic reduction of N2O by CO molecule. It is found that the adsorption and decomposition of N2O molecule over Si-GO is more favorable than over Al-GO, due to its larger adsorption energy (Eads) and charge transfer (qCT) values. On the other hand, the CO molecule is physically adsorbed over both surfaces, with relatively small Eads and qCT values. Therefore, at the presence of N2O and CO molecules as the reaction gas, the Al or Si atom of the surface should be dominantly covered by N2O molecule. Our results indicate that the N2O decomposition process can take place with a negligible activation energy over Al-/Si-GO surface, where the N2 molecule can be easily released from the surface. Then, the activated oxygen atom (Oads) which remains over the surface reacts with the CO molecule to form the CO2 molecule via the reaction Oads+CO→CO2. Based on the calculated activation energies, it is suggested that both Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N2O molecule at ambient conditions.