Pd- and Pt-Doped Graphene Quantum Dots for SO2 Adsorption and Dissociation: A Non-periodic DFT Study

Commonly, transition metal catalysts such as Pt and Pd are used to adsorb and dissociate SO2 gas. Usually, SO2 adsorption energies on these metals are in the range of -1.0 to -1.5 eV, and the barrier energies are in the range of +0.5 to +1.0 eV. These small values of barrier energies cause that SO2 is readily converted to atomic sulfur, and the catalysts surfaces are poisoned by sulfur. In this paper, Pd- and Pt-doped graphene quantum dots are proposed as SO2 removal catalysts from flue gas emission. SO2 removal catalysts should have high barrier energy to prevent sulfur formation from SO2 dissociation, but have moderate SO2 adsorption energy to simply adsorb and desorb SO2. Using non-periodic density functional theory, the adsorption and dissociation of SO2 on Pd- and Pt-doped graphene quantum dots are investigated to test whether these catalysts are suitable for SO2 removal. The data show that the adsorption energies of SO2 on Pt- and Pd-doped graphene are in the range of -0.6 to -0.8 eV and -0.6 to -1.0 eV, respectively. However, their barrier energies are greater than +2.0 eV which is more than twice those on the transition metal surfaces. While these catalysts are good candidates for SO2 removal, they are not suitable for SO2 dissociation. The high barrier energies, contrary to the pristine transition metal surfaces, prevent the poisoning of the surfaces of the studied catalysts.

Pd- and Pt-Doped Graphene Quantum Dots for SO2 Adsorption and Dissociation: A Non-periodic DFT Study Keywords:

SO2 adsorption , SO2 reduction , Pt-doped , Pd-doped , Graphene quantum dot