Pd- and Pt-Doped Graphene Quantum Dots for SO۲ Adsorption and Dissociation: A Non-periodic DFT Study

Commonly, transition metal catalysts such as Pt and Pd are used to adsorb and dissociate SO۲ gas. Usually, SO۲ adsorption energies on these metals are in the range of -۱.۰ to -۱.۵ eV, and the barrier energies are in the range of +۰.۵ to +۱.۰ eV. These small values of barrier energies cause that SO۲ 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 SO۲ removal catalysts from flue gas emission. SO۲ removal catalysts should have high barrier energy to prevent sulfur formation from SO۲ dissociation, but have moderate SO۲ adsorption energy to simply adsorb and desorb SO۲. Using non-periodic density functional theory, the adsorption and dissociation of SO۲ on Pd- and Pt-doped graphene quantum dots are investigated to test whether these catalysts are suitable for SO۲ removal. The data show that the adsorption energies of SO۲ on Pt- and Pd-doped graphene are in the range of -۰.۶ to -۰.۸ eV and -۰.۶ to -۱.۰ eV, respectively. However, their barrier energies are greater than +۲.۰ eV which is more than twice those on the transition metal surfaces. While these catalysts are good candidates for SO۲ removal, they are not suitable for SO۲ dissociation. The high barrier energies, contrary to the pristine transition metal surfaces, prevent the poisoning of the surfaces of the studied catalysts.

کلیدواژه ها:

SO۲ adsorption ، SO۲ reduction ، Pt-doped ، Pd-doped ، Graphene quantum dot