Water splitting and CO 2 reduction over an AgSr 2 Ta 5 O 15 photocatalyst developed by a valence band control strategy.

Ag + substitution was applied to a tungsten-bronze-type metal oxide. An AgSr 2 Ta 5 O 15 photocatalyst has emerged for water splitting and CO 2 reduction. DFT calculation and diffuse reflection spectra revealed that the Ag d-orbital formed a new valence band, leading to a narrow band gap (3.91 eV) compared to that of NaSr 2 Ta 5 O 15 (4.11 eV).