The doping of foreign cations and anions is one of the effective strategies for engineering defects and modulating the optical, electronic, and surface properties that directly govern the photocatalytic O 2 and H 2 evolution reactions. BaTaO 2 N (BTON) is a promising 600 nm-class photocatalyst because of its absorption of visible light up to 660 nm, small band gap (E g = 1.9 eV), appropriate valence band-edge position for oxygen evolution, good stability under light irradiation in concentrated alkaline solutions, and nontoxicity. Although the photocatalytic and photoelectrochemical water-splitting efficiencies of BaTaO 2 N have been progressively improved, it is still far from the requirements set for practical applications. Here, we employ a 5% B site-selective doping of aliovalent metal cations (Al 3+ , Ga 3+ , Mg 2+ , Sc 3+ , and Zr 4+ ) to enhance sacrificial visible light-induced photocatalytic H 2 and O 2 evolution over BaTaO 2 N. The results of physicochemical characterizations reveal that no significant change in crystal structure, crystal morphology, and optical absorption edge is observed upon cation doping. Therefore, the difference observed in O 2 and H 2 evolution during the photocatalytic reactions over pristine and doped BaTaO 2 N photocatalysts is explained by examining optical, electronic, and surface properties. Also, molecular dynamics (MD) is used to gain insights into the respective effect of cation doping on adsorption energy of water molecules and formed intermediates (H* for H 2 evolution and HO*, O*, and HOO* for O 2 evolution) on the BaTaO 2 N surfaces terminated with TaO 6 , TaN 6 , and TaO 4 N 2 octahedra. Finally, the experimental reaction rates for H 2 and O 2 evolution are correlated well using a linear energy−performance relationship, elucidating the doping and surface-termination trends observed in the BaTaO 2 N photocatalysts.

No abstract

No abstract