Understanding the Photocatalytic Activity of La 5 Ti 2 AgS 5 O 7 and La 5 Ti 2 CuS 5 O 7 for Green Hydrogen Production: Computational Insights.

Green production of hydrogen is possible with photocatalytic water splitting, where hydrogen is produced while water is reduced by using energy derived from light. In this study, density functional theory (DFT) is employed to gain insights into the photocatalytic performance of La 5 Ti 2 AgS 5 O 7 and La 5 Ti 2 CuS 5 O 7 -two emerging candidate materials for water splitting. The electronic structure of both bulk materials was calculated by using hybrid DFT, which indicated the band gaps and charge carrier effective masses are suitable for photocatalytic water splitting. Notably, the unique one-dimensional octahedral TiO x S 6- x and tetragonal MS 4 channels formed provide a structural separation for photoexcited charge carriers which should inhibit charge recombination. Band alignments of surfaces that appear on the Wulff constructions of 12 nonpolar symmetric surface slabs were calculated by using hybrid DFT for each of the materials. All surfaces of La 5 Ti 2 AgS 5 O 7 have band edge positions suitable for hydrogen evolution; however, the small overpotentials on the largest facets likely decrease the photocatalytic activity. In La 5 Ti 2 CuS 5 O 7 , 72% of the surface area can support oxygen evolution thermodynamically and kinetically. Based on their similar electronic structures, La 5 Ti 2 AgS 5 O 7 and La 5 Ti 2 CuS 5 O 7 could be effectively employed in Z-scheme photocatalytic water splitting.