Graphyne-supported single Fe atom catalysts for CO oxidation

Single atom catalysts (SACs) are highly desirable for the effort to maximize the efficiency of metal atom use. However, the synthesis of SACs is a major challenge that largely depends on finding an appropriate supporting substrate to achieve a well-defined and highly dispersed single atom. This work demonstrates that, based on the density functional theory (DFT) calculation, graphyne is a good substrate for single Fe atom catalysts. The Fe atom can be tightly embedded in a graphyne sheet with a high binding energy of similar to 4.99 eV and a high diffusion energy barrier of similar to 1.0 eV. The graphyne-supported Fe (Fe-graphyne) SAC shows high catalytic activity towards CO oxidation, which is often regarded as a prototype reaction for designing atomic-scale catalysts. We studied the adsorption characteristics of CO and O-2 on Fe-graphyne SACs, and simulated the reaction mechanism of CO oxidation involving Fe-graphyne. The simulation results indicate that O-2 binding on Fe-graphyne is much stronger than that of CO, and the adsorbed O-2 prior to occupy the Fe atoms as the co-existence of O-2 and CO. The reaction of CO oxidation by adsorbed O-2 on Fe-graphyne SACs favors to proceed via the Eley-Rideal (ER) mechanism with the energy barrier of as low as similar to 0.21 eV in the rate-limiting step. Calculation of the electronic density of states (DOS) of each reaction step demonstrates that the strong interaction of the O-2 and Fe adatom promotes the CO oxidation on Fe-graphyne SACs. The results presented here suggest that graphyne could provide a unique platform to synthesize SACs, and the Fe-graphyne SACs could find potential use in solving the growing environmental problems caused by CO emission from automobiles and industrial processes, in removing CO contamination from vehicle exhaust and in fuel cells.