Stable, while Still Active? A DFT Study of Cu, Ag, and Au Single Atoms at the C₃N₄/TiO₂ Interface

Hybrid DFT calculations are employed to compare the adsorption and stabilization of Cu, Ag, and Au atoms on graphitic C₃N₄ and on the heterojunction formed by g- C₃N₄ and TiO₂. While Cu and Ag can be strongly chemisorbed in form of cations on g- C₃N₄, Au is only weakly physisorbed. On g- C₃N₄/TiO₂, all coinage metal adatoms can be strongly chemisorbed, but, while Cu and Ag forms cations, Au form an Au^- species. Ab Initio Molecular Dynamics simulations confirm that the metal adatoms on g-C₃N₄ are highly mobile at room temperature, while they remain confined in the interfacial spacing between C₃N₄ and TiO₂ on the heterojunction, being both stably bound and reachable for the reactants in a catalytic cycle. Doping g- C₃N₄/TiO₂ with metal single atoms permits thus to generate catalytic systems with tunable charge and chemical properties and improved stability with respect to bare C₃N₄. Moreover, the changes in the electronic structure of g- C₃N₄/TiO₂ induced by the presence of the metal single atoms are beneficial also for photocatalytic applications.