A Theoretical Investigation on the Structural, Electronic and Photocatalytic Properties of BaTaO₂N Adsorbed with Metal Cocatalysts

We have performed DFT calculations to study the adsorption of single metal atoms (M=Ti, V, Cr, Mn, Fe, Co, Ni, Cu) on both BaO- and TaON-terminated surfaces of cis-BaTaO₂N (001). We have identified the most stable adsorption configuration of each case and explored the relative stability, structural deformations, charge transfer, work function, density of states and mechanism of photocatalytic HER. For BaO termination, all of the adatoms bind covalently on top of the surface oxygens. For TaON termination, the metal atoms are located at the fourfold hollow site. The single metal atoms tend to exist on TaON-termination while they are apt to aggregate on BaO-termination. The formation of impurity states in the band gap is mostly originated from the adatom. When electrons are transferred from the adatom to the surface, the conduction band of semiconductor becomes partially occupied. The charge gained from the BaO termination or transferred to the TaON termination reduces with the increase in electronegativity of metal adatoms. The attachment of metal atoms on the BaO termination is favorable to the improvement of HER activity. While the TaON termination adsorbed with Ti, V and Cr may have better or comparable performance of HER compared with the pure surface.