Unique reactivity of Fe nanoparticles-defective graphene composites toward NHx (x=0, 1, 2, 3) adsorption: a first-principles study

We investigated the electronic structure of Fe nanoparticle-graphene composites and the impact of the interfacial interaction on NHx (x = 0, 1, 2, 3) adsorption by first-principles based calculations. We found that Fe-13 nanoparticles can be stabilized by the sp(2) dangling bonds on single vacancy graphene substrate with a binding energy up to -7.07 eV. This interaction not only deformed the carbon atoms around the defect and gave rise to the stability of the Fe nanoparticle against sintering, but also had significant impact on the adsorption of NHx that is related to the catalytic performance of these composites in NH3 decomposition. Doping of the single vacancy graphene with N or B can finely tune the adsorption of NHx. Further analysis revealed that the calculated adsorption energies of NHx on these composites correlated well with the shift of the average d-band center of the Fe nanoparticles and they were around the peak of the activity-adsorption energy curve for NH3 decomposition catalysts, especially when doped with B. The optimal adsorption of NHx on Fe nanoparticles deposited on boron-doped defective graphene suggests the possible high stability and superior catalytic performance of these composites in the low-temperature catalytic decomposition of NH3.