First-Principles Investigation on Electronic Properties and Surface Reactions of NaTaO3 Adsorbed with Single-Metal Atoms

The rational design of cocatalysts in a photocatalytic system is necessary to improve the reaction activity since they can act as the reaction sites and promote the separation of photogenerated carriers. In this work, we have performed detailed density functional theory calculations on the effect of adsorbing single-metal atoms (M = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) on the surface structure, electronic structure, work function, charge transfer, and photocatalytic reaction mechanism of the NaTaO3(001) surface. Our results reveal that the adsorption of metal atoms on the NaO-terminated surface is more stable than that on the TaO2-terminated surface. The formation of multiple new bonds and the surface reconstruction are in favor of stabilizing the studied systems. The impurity states in the forbidden gap mostly originate from the hybridized nd orbitals of the adsorbed metal atoms and Ta atoms. The adsorption energies of the metal atoms are related to the bond lengths of metal-oxygen bonds and the amounts of interfacial charge transfer. It is found that a decrease in the work function of the surface is fairly proportional to the charge gained from the metal adatom, which indicates that the work function of NaTaO3 can be regulated by the type of the metal adatom. Loading 3d metal atoms on the surface has better performance than 4d and 5d metal atoms in enhancing the activity of hydrogen evolution reaction. The performance of Co as the oxidation cocatalyst is better than other metals since its adsorption on the surface decreases the overpotential of oxygen evolution reaction by more than 1.1 V. The adsorption of single metal atoms on the NaTaO3 surface is favorable to the activation of CO2 due to the elongated C=O bonds and the bent configuration of the CO2 molecule. The results of the present study can be employed in synthesizing optimal photocatalysts.