No Reduction Over Highly Dispersed Zerovalent Iron (Fe0) Supported on Graphene: A Mechanistic Study Using In-Situ Ftir and Dft Calculations

NO reduction over highly dispersed zerovalent iron (Fe0) supported on graphene (G), with and without the presence of CO in the reacting stream, was systematically studied using a fixed-bed reactor and the reaction mechanism examined with the aid of in-situ Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) calculations. The in-situ FTIR results showed that NO adsorbed on Fe0 site is reduced to form active surface oxygen species (O*) which is then reduced by a carbon in graphene to form CO2. The presence of CO in the reacting stream helps to reduce the oxidised Fe(O) sites to regenerate Fe0 sites, making NO reduction easier. It was revealed that NO and CO2 are easily adsorbed on the active surface oxygen species (O*) to form nitrate and carbonate, inhibiting their reduction by CO and deactivating the catalyst. The DFT calculations results suggest that the role of Fe is to reduce the energy barrier of the NO decomposition, which controls the formation of active surface oxygen species and CO2. The combined FTIR and DFT results offer a new insight into the possible mechanism of catalytic NO reduction over graphene loaded with Fe, with and without CO.